Engine Sensors
Contents
1. O2 signal in your 960 undo the red and blue four way 02 connector near the oil dipstick and check inside The metal spades in the male connector are surrounded by silicone like material which crumbles particularly after you apply electronic connection cleaner or the like The particles can fall within the male and female connection even inside the female connector contacts and cause a faulty O2 sensor signal Take out the loose material with sharp tweezers Make sure all contacts are clean and undistorted and connect back together WITHOUT using silicone dielectric grease because of low signal voltages Clear the codes This procedure should eliminate the faulty signal Crank Position or RPM Sensor B2XX Series Engines Symptoms of Failure No Hot Restart Suppose the car already has the upgraded silver terminal fuel pump relay but won t restart promptly after a hot soak Take an educated guess on a weak crank position RPM sensor If you have Bosch LH2 4 then replacing this permanent magnet sensor located in the top of the bellhousing fixes many hot restart complaints on 700 900s Tip from HansW Check the lead to the sensor it can rub against engine components or fray from flexing and expose the wiring Newer sensors come with plastic cable holders to prevent this Editor Many Regin equipped cars use the same sensor Testing Bellhousing RPM Sensor nquiry decided to find and remove my flywheel sensor Externally it s i2. crows foot or special slotted O2 sensor socket or adapted open closed end wrench Replacement Procedure Editor Tom s notes apply to a 960 but the procedure is similar for 740 940 query I m planning to change my O2 sensor on my 960 wagon Where is that thing How tough of a time will have in removing it because of heat related seizing Response Tom Irwin OK if you are w o a shop and hydraulic lift recommend the following FOUR JACKSTANDS Rated to 3 000 pounds apiece or better I ve been lifting the car under it s mid chassis reinforcement with a large wide saddle jack A skinny jack will damage the underside of your car Lifting the whole side place 1 jackstand each under the corner lifting points at FULL EXTENSION do the drivers side first Ditto the passenger side BUT LEAVE the jack in place and lower it maybe 0 5 so itis a back up in case the jackstands fail but it is NOT bearing any load could cause they whole deal to shift Lay down a HEAVY piece of corrugated cardboard Let s you SLIDE in and out from under the car real nice The O2 sensor is screwed in to the CAT up on top there are four wires FIRST Go open the hood and locate the O2 connector it s kinda near the oil dipstick tube about half way down It should be clipped to a metal standard release it there is enough slack to lift the whole assembly up higher for a better look It is a BLUE plastic connector with a RED slide Lock passing through
3. 20 C and 200 at 212 F 100 C However try checking your ECT wiring Between pins 13 and 5 at the LH ECU with sensor DISconnected resistance should be infinite Voltage with the ignition ON and sensor connected measured between pins 13 and 5 should be e 0 C around 3 volts 5v e 20C around 2 volts 5v e 100C around 3 volt 1v If these aren t correct check the connections in the ECT wiring harness Check engine ground connections at the intake manifold If the voltage is zero your ECU is at fault ECT Wiring Connector Failure JonP my 1990 LH2 4 still ran rich smoked stumbled and set codes 1 1 3 2 1 3 and others refering to rich mixture However during disassembly discovered the female connector for the ECT was file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors damaged by one of the sensors spade pins when someone pressed the connector on incorrectly The pin missed one of the female clips and mashed it The local Volvo dealer parts manager has been very helpful described the ECT connector problem and he gave a new connector to me with a couple of insulated pinch connectors and his tips for how to make the splice no charge He did say if this splice didn t fix it then he thought it was a failed ground in the ECU ECM for the fuel injection He said the bad connector could also cause a bad ground problem at the ECU 960 B6304 ECT Sensor Fail
4. B23X engines except for the wiring clip on the firewall DanR To get the connector off the bracket all you need is a fairly small flat bladed screw driver Pry away the metal collar that surrounds the connector it has a clip that snaps in place The part that snaps in is on the underside of the clip If you break the plastic shells holding it together they are replaceable from the dealer On reinstallation make sure you insert correctly the two wires from the trans oil temp sensor Knock Sensor file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors Symptoms of Failure Tips from Marc The car starts fine and will run for 2 miles and then lose power It never stalls just won t move If I shut it off and immediately restart it it will run fine again for another 2 miles and so on and so on When it runs fine with a timing light hooked up on acceleration the timing will retard 1 or 2 degrees before it advances If check it when the problem is occuring it will retard 6 or 8 degrees before it tries to advance Solution new knock sensor Other symptoms Retarded timing acting as though no fuel is reaching the engine Sensor Styles John Sargent The knock sensor is located on the cylinder head under the junction between number two and three intake manifold runners It is next to the two coolant temperature sensors also bolted to the head LH 2 1 LH 2 2 and LH 2 4 all use t
5. is a little tougher since it is buried under intake manifold runner number three Two contrary removal tips Tip from John Sargent Removing the intake manifold makes it less than a 30 minute job Trying to R amp R without removing the intake manifold can lead to a broken sensor The brass hex of the ECT is 19mm The electrical connector is larger than the 19mm hex and a socket or box end wrench will not fit over the electrical connector SO you Can only use an open end wrench to remove the ECT The wiring harness connector can be very difficult to disconnect without removing the intake manifold Save yourself on both aggravations just get an intake manifold gasket if the sensor needs to be replaced Jay Simkin This sensor s wiring connector housing fits inside a 19mm deep socket which then engages the sensor s brass hex fitting recently did this job and used a 3 8 19mm deep socket to remove the sensor from the head There was just enough work room between the manifold s runners have small hands put the socket on the sensor and then inserted the ratchet s square protrusion into the socket By contrast the temperature gauge s coolant sensor towards the front of the head has a wiring connector housing wider than is the sensor s brass hex fitting Therefore some may need to remove the connector housing before removing the sensor Installing the Sensors Editor Do NOT use Teflon tape or Teflon pipe sealer on the threads w
6. it s mid section Use a small thin screwdriver under the looped bail of the red slide lock and pry it gently to the side extend it as far as it will go Separate the 2 blue plastic halves make sure that the end of the harness that goes down below to the O2 sensor is not wire tied anywhere Go back Down Under the car pull the wire down and cut any cable ties holding it to the dipstick or elswhere Now on the left side of the transmission there are 3 plastic snap lock clips holding the wires to the transmission pan Squeeze them from the inside with a thin nosed plier and release all three On the UPPER TRAILING EDGE of the transmission tail bracket there are 3 10mm headed bolts file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors holding the wire to the bracket Remove all three A small 1 4 drive ratchet is great for this Then remove the ONE speed nut holding the wire up on a heatshield in front of the CAT Follow the wire THAR she IS sticking out of the top of the CAT in front of the honeycomb It is a 22mm facet on the base of the sensor Get a 22mm socket with the sidewall slotted out for the wire to pass thru Editor known as an oxygen sensor wrench if you can but just squirted a bit of PB Blaster on the base and let it sit for a few minutes ended up using a 22mm spanner wrench open end to the sensor It cracked free quite easily you may be so lucky Th
7. output to drop to its minimum 0 1v value Although a technician can read the O2 sensor s output with a scan tool or digital voltmeter the transitions are hard to see because the numbers jump around so much An analog voltmeter is better for viewing transitions but may not respond quickly enough on systems with higher transition rates So the recommended instrument for observing the O2 sensor s voltage output is a digital storage oscilloscope DSO A scope will display the sensor s voltage output as a wavy line that shows its amplitude minimum and maximum voltage as well as its frequency transition rate from rich to lean A good O2 sensor should produce an oscillating waveform at idle that makes voltage transitions from near minimum to near maximum If the sensor doesn t flip flop back and forth quickly enough it may indicate a need for replacement If the O2 sensor circuit opens shorts or goes out of range it may set a fault code and illuminate the Check Engine or Malfunction Indicator Lamp If additional diagnosis reveals the sensor is defective replacement is required Specific Diagnostics and Tests See the specific diagnostic procedures in the FAQ Fuel Injection section on Oxygen Sensor Diagnosis Inquiry Anybody know what the resistance of the O2 sensor heater should be file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors mine says 2 2 ohms With only the gre
8. silicone based RTV gasket file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors material anywhere on the engine especially in manifolds or valve covers make sure the tube says sensor safe RTV compound Silicone from the gasket can contaminate your oxygen sensor According to the Robert Bosch Corp replacing a degraded oxygen sensor with a new one will increase fuel efficiency by 10 to 15 Don t use silicone sprays anywhere near the intake system And Airtex Automotive reports replacing degraded oxygen sensors has the potential to reduce a vehicle s emissions of hydrocarbons HC by 23 and carbon monoxide CO by 33 In fact an EPA study found that 70 of the vehicles that failed an I M 240 emissions test needed a new O2 sensor Bosch recommends a professional service technician check a customer s oxygen sensor on a regular basis every 60 000 to 100 000 miles for a heated three or four wire sensor The O2 sensor works like a miniature generator and produces its own voltage when it gets hot Inside the vented cover on the end of the sensor that screws into the exhaust manifold is a zirconium ceramic bulb The bulb is HEATER coated on the outside with a porous layer of platinum CIRCUT Inside the bulb are two strips of platinum that serve as AMBIENT AIR electrodes or contacts Between the electrodes is a solid state electrolyte made up of a Zirconic ceramic mate
9. was not very tight anyhow just very hard to get to Tom Irwin Those rear ECT s are a pain in the ass The harness surprise allows very little slack As the insulation degrades the tension on the wires just pops it off Then the epoxy potting around the sensor starts to go Throttle Position Switch Editor This applies to both Bosch LH2 4 and Regina systems Symptoms of Failure High idle at startup or uncontrolled idle above 750 rpm Diagnosis This switch is a simple device at either extreme of motion an internal switch is closed and you will see continuity between one outer connector and the middle ground connector Disconnect the file Cl Users Steve Documents Volvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors switch connector and jump from one side connector to the middle ground connector If idle returns to normal then the switch is at fault The switch is not repairable Adjusting the TPS To adjust the TPS 1 Remove the throttle body from the car and loosen the TPS adjustment screws 2 Hold the throttle plate and keep it from moving Rotate the TPS clockwise then counterclockwise until a click is heard Continue rotating until it stops but does not cause the throttle plate to move This can z best be done by inserting a 25mm feeler gauge sical between the lever and the adjustment screw Secure the screws 3 Proper adjustment is obtained when you open the throttle plate
10. your mouth you can make a more hygienic mouthpiece from a couple of inches of scrap vacuum hose When cleaned my valve it had very little carbon dirt in the valve Noticeable build up of carbon on end of the EGR discharge pipe where it connects to the intake manifold Cleaned this up with a stiff wire and several squirts of throttle body cleaner EGR Valve Reinstallation put a little anti seize on the threads before replacement don t get any inside the ports though am hoping this will make it easier to get the nuts off next time Place the valve in its bracket Hand tighten clamping nut that holds it to the bracket Start the threads on the two acorn nuts Attach the outlet pipe to the intake manifold and tighten the nuts there all the way Tighten the bracket clamping nut all the way Tighten the two acorn nuts all the way Put a spot of silicone grease on the vacuum nipple and replace the vacuum tube again am hoping this will stop the rubber from gluing itself to the nipple Reconnect the temp sensor electrical connector Pulsair Valve Tops from Tom F Volvo introduced Pulsair system on B200 30A E and K engines and on the US 94 95 B230FD engines The Pulsed Secondary Air injection system adds oxygen to the exhaust Ma BAIARD AM ARE Aas E manifold to d continue the me combustion of unburned fuel in the exhaust system and provides additional oxygen for the catalytic converter thereby lowering harmful emissions It is in
11. 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors valve so took the valve off with this pipe still connected disconnect the other end of the pipe from the intake manifold first The valve is held on a bracket with a 25mm nut managed to get this off with a 1 inch AF open ended wrench Again it took some force to break it free and access is limited so it was 1 6 or 1 4 turn at a time to get the nut off had a difficult time getting the vacuum hose off the valve the rubber boot at the end of the hose was in very poor conditon rubber was breaking down and had taken on a tacky gummy consistency and was stuck to the vacuum nipple on the valve assume this is due to the high temps that this valve sees will be looking for a replacement as do not think it is going to last much longer EGR Valve Vacuum Checking Cleaning If you don t have a vacuum pump to test operation improvise Insert an allen wrench or small screwdriver or other Suitable probe into the inlet port threaded opening on the end of the valve until it contacts the valve seat Keep one hand on this probe while maintaining a small force to keep it in contact with the seat Place vacuum nipple in mouth and suck You will feel the valve seat opening The valve should hold open without any additional suction If the valve fails to open or if the diaphragm leaks when you do this then the valve may need to be replaced If you don t want to put engine parts in
12. CT which is in effect two sensors in one housing Two NTC thermistors are combined in one ECT sensor housing with two flat connectors and ground through the housing into the manifold One of the temp sensor signals goes to the LH fuel injection computer the other to the EZK ignition computer When you remove any of the sensors disconnect the battery negative cable Removing the Sensors Do Need to Drain the Coolant John McRaven Release any residual pressure in the system by opening the cap then close it again Get the old ECT loose get the new one ready to go then just pop the old one out and put the new one in as quickly as possible You really won t lose very much coolant at all The sealed system will glug out a little bit then build a slight vacuum and stop Put the new one in tighten then rinse away the slight leakage with a hose and top off the missing pint or less Gauge Temperature Sensor Inquiry How do I remove the gauge temperature sensor Mark Duval This is the front sensor under intake manifold runner number two with the two round pins A 19mm socket will not work because of the width of the wiring connector bought the stubby 19mm combination wrench and a 19mm crow foot socket First tried the open end side of the stubby and although could get it squarely on the hex head could not put enough force on the wrench to turn the sensor Then used the crow foot socket with a long extension This rotated off the h
13. Engine Sensors Electrical Engine Sensors FAQ Home Volvo Maintenance FAQ for 7xx 9xx 90 Cars Air Mass Meter Hall Sensor Engine Temperature Sensors Diagnosing ECT Failures 960 B6304 ECT Sensor Failure Throttle Position Switch Oxygen Sensor Crank Position or RPM Sensor Knock Sensor EGR Valve Pulsair Valve Regina Air Temperature Sensor Regina Manifold Air Pressure Sensor Abbreviations AMM Air Mass Meter ECT Engine Coolant Temperature sensor ECU Engine Control Unit computer either fuel injection or ignition FI Fuel Injection FPR Fuel Pressure Regulator IAC Idle Air Control solenoid valve TB Throttle Body TPS Throttle Position Sensor VSS Vehicle Speed Sensor file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors Air Mass Meter See FAQ section in Engine Fuel Injection for AMM information Hall Sensor See Electrical Ignition for more details on Hall sensors in LH 2 2 and earlier distributors Engine Temperature Sensors The B230F of the vintage discussed 1989 1995 have in effect three temp sensors The Temperature Gauge Sensor is at the front under intake manifold runner number two just ahead of the knock sensor which is bolted in at an angle It has two round pin connectors one signal one ground For resistance ratings see the link noted Behind the knock sensor under manifold runner three is the Engine Coolant Temperature Sensor E
14. When the O2 sensor reading goes lean low voltage the computer reverses again making the fuel mixture go rich This constant flip flopping back and forth of the fuel mixture occurs at different speeds depending on the fuel system Engines with multiport injection do this five to seven times per second at 2 500 rpm The O2 sensor must react quickly to these changing fuel conditions in order for the computer to maintain the best average air fuel ratio As sensors age they become sluggish and respond more slowly to changes in the air fuel ratio This may cause emissions and fuel consumption to rise Before it will start to generate a voltage signal the oxygen sensor must be hot usually from about 450d F to 600d F or even higher The sensor incorporates an internal electric heating element to bring the O2 sensor up to operating file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors temperature quickly under 35 seconds Internal heating elements usually operate continuously while the engine is running to maintain an operating temperature of approximately 1292 degrees Fahrenheit to 1472 degrees Fahrenheit Heated O2 sensors operate at a more consistent temperature and allow greater flexibility of placement locations in the exhaust system Three and four wire sensors have this heater installed two wires for the heating element one signal wire and possibly a ground wire Oxygen sensors tha
15. a cars A direct replacement for the Regina sensor is an NGK 25002 Amazon has a good price on these When is Replacement Recommended Tip from Import Car Magazine Apr 2003 Replace if e Antifreeze contaminates oxygen sensors Oxygen sensor replacement is highly recommended after replacing cracked cylinder heads leaking intake gaskets or file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors leaking cylinder head gaskets e Oil contamination also ruins oxygen sensors Oil ash accumulating on the sensor thimble or wicking through the sensor wire may cause erroneous air fuel ratio readings Other Conditions Causing Oxygen Sensor Malfunctions e Leaking exhaust manifolds and air injection systems contribute to faulty air fuel measurements by the oxygen sensor because they dilute the exhaust gas stream with atmospheric oxygen e Leaking fuel pressure regulators or leaking vacuum hoses and intake gaskets often will cause a no switching condition at the oxygen sensor Replacement Procedures Opening Caution J ohnO If doing it yourself do it with a cold engine as many O2 sensors are more likely to cross thread if done hot although not so much so with Volvos If you doubt your skills with this just take it to dealer and pay them to replace it as it won t be that much for the labor about 1 hour Tool Notes Which tool do use to remove the O2 sensor Paul Seminara Us a
16. acket is to pull the transmission and replace it However have seen reports of using a Dremel or drill along with a shop vac to suck up metal chips to enlarge the bellhousing opening and remove the bracket screws before installing a new sensor bracket This is done without pulling the transmission Robert Drill and a dremel worked fine Tried to pull tranny out but got stuck on one pesky bolt So had to abort and went for a drill Was done in 2 hours and back on the road today only had to trim about half an inch on each side The bracket itself is only about 30 Bent Flywheel Sensor Plate The sensor uses a toothed plate mounted on the flywheel to sense revolutions if this is bent it will not record the pulse Odd symptoms including difficult starting and poor power may result Bending commonly occurs when working around the flywheel or when jamming the ring gear to change the timing belt so be VERY careful when working in that area B6XXX Series Six Cylinder Engines Tip Rob Bareiss The 960 B6304 engine uses a sensor mounted at the back end of one of the camshafts It s in the same position as the distributor on an 850 S V70 5cylinder Since the 960 has no distributor it uses this thing instead Also saves a bunch of space at the back of the engine Probably should consider it a regular service item as with the 4 cylinder models Replacing it is probably cheaper than having the car towed one time Removing it is similar to the
17. and air fuel ratio You can check this resistance by connecting an ohmmeter between pins to read e 20 C 4 F 15K ohms e 20 C 68 F 2 5K ohms e 100 C 212 F 160 ohms Use a heat gun to change temperature Problems may occur in the sensor the connector or the wiring leads Regina Manifold Air Pressure MAP Sensor The Regina fuel injection system uses air pressure and temperature in the intake system to compute the air mass moving into the engine The MAP pressure sensor is located on the driver s strut tower support It is connected to the intake manifold through a hose and takes a reading of intake pressure The sensor is piezo electric and changes a voltage input to an output signal proportional to manifold pressure The system calibrates file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors atmospheric pressure when the engine is started and under full load conditions To test turn ignition on and test the back of the sensor connector or the pins on the back of the ECU connector do not disconnect with the ignition on e Connector A or pin 6 is ground e Connector C is the constant voltage input from pin 7 on the ECU and should read 5 volts to ground e Connector B is the variable output signal from the pressure sensor to pin 11 on the ECU Connect a hand vacuum pump to B or 11 apply vacuum and read the signal Voltage should drop from 5 volts to a lower numbe
18. and insert a feeler gauge at the throttle stop screw o When you close the throttle against a 45mm feeler gauge no click is heard from the TPS o When you close the throttle against a 15mm feeler gauge a click is heard Oxygen Sensor Theory and Operation 1 Oxygen sensors should last over 100k miles under ideal conditions various contaminants will shorten that considerably 2 Excerpts from Underhood Service magazine Nov 2000 et al The O2 sensor is mounted in the exhaust manifold to monitor how much unburned oxygen is in the exhaust as it exits the engine Monitoring oxygen levels in 1 the exhaust is a way it gauges the fuel mixture The sensor tells the computer if the fuel mixture is burning rich less oxygen or lean more oxygen Although O2 sensors are amazingly rugged considering the operating environment they live in they do wear out and eventually have to be replaced The performance of the O2 sensor diminishes with age as contaminants accumulate on the sensor tip and gradually reduce its ability to produce voltage The aging process is caused by a buildup of contaminants on the sensor s zirconium sensing element If the engine burns oil phosphorus deposits may contaminate the sensor and catalytic converter over time If the engine has an internal coolant leak cracked combustion chamber or leaky head gasket silicone additives in the antifreeze can become a source of contamination Contamination Caution If you use
19. arrow space Put it somewhere safe Removing the Sensor The sensor usually will come free as soon as the screw is removed If it does not grip it close to where it enters the housing not at the top into which the wire enters and pull straight up Do not pull on the wire If the sensor will not come out you may need to break any seal between the sensor base and the bell housing Use penetrating oil Turn the sensor gently about 1 16 turn in either direction You may rock the sensor gently but no more than 1 16 side to side Do not use any tool or brute force and DO NOT PRY since the housing is plastic see the Cautionary Note below The sensor goes only about 3 4 into the bell housing The sensor has smooth sides and no locking lugs so it is removed by pulling straight up Do not use brute force if the sensor snaps and plastic fragments fall into the bell housing the transmission will have to be removed to allow removal of the fragments Disconnect the sensor at the connector near the driver s side firewall Pry the spring clip loose and put it safely somewhere It s file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors small and easily lost You can fish the plug through the zip tie on the firewall but it s not all that easy Move the other wires etc until you get it out Caution Some Cars Have a Flimsy Sensor Mounting Bracket Another Tip Trouble started when co
20. ch a mixture because of a failing ECT may lead to idle surges high idle poor warm running or other symptoms of too much fuel See Engine Tune and Performance Symptoms for more examples If the control unit receives a signal higher than 302F 150C or lower than 40F 40C it will interpret the signal as a fault the control unit will assume a substitute value corresponding to 32F OC on starting and 68F 20C when the engine has started With the control unit connected connect a voltmeter across LH ECU terminals 13 and 5 ground for Bosch LH 2 4 systems or terminals 2 and 5 ground for LH 2 2 systems This unit is in the passenger side footwell under the plastic cover Remove the cover of the large electrical connector to access the backs of the pins for the test Turn the ignition switch ON e At 68F 20C the voltage should be 2 0 5v volts e At 104F 40C the voltage should be 1 2 3volts e At 176F 80C the voltage should be 5 2volts The resistance values between ECU pins 13 and 5 or between each of the pins on the sensor and ground are by eye from the chart e 32F OC about 6000 ohms within a range of 10 e 68F 20C about 2300 ohms e 104F 40C about 1300 ohms e 140F 60C about 600 ohms e 176F 80C about 300 ohms e 212F about 190 ohms Response Steve Ringlee ECT resistance cold for LH2 4 systems should be around 6k ohms at 32 degrees F 0 deg C 2300 2700 ohms at 68 degrees F
21. closed throttle signal is supplied to Chrysler ignition ECU and it cancels knock sensor retard activity If you have Bosch ignition systems you can t do the whack it and watch it test for knock sensor operation The Bosch systems are cylinder specific and you would have to knock within a few crank degrees of a given cylinder firing and be monitoring the timing light attached to that cylinder s plug wire don t think any of us are that good Tip for Chrysler Ignition Systems from Duane Hoberg On the right side of the engine in the area above and to the rear of the oil filter tap the block with a metal faced hammer while observing the timing with a timing light The timing should retard 6 degrees then return If not then the sensor or the circuit in the control box is bad When installing the new knock sensor use thread lock Apply too much torque and the sensor becomes sensitive as it is prestressed and reacts to normal file Cl Users Steve Documents Volvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors engine vibration When this happens you will idle fine but above idle run at retarded timing all the time Acts like poor fuel delivery and doesn t like hills Diagnosis Additional Tips from Dave Stevens Procedures for dealing with suspected knock sensor problems for an LH 2 4 system with EZ116 K ignition Tests for other systems will be similar Check the wiring diagram for your particular model and year to ve
22. d be replaced if they are black from soot They do wear out Tom There are two tubes that come off the manifold that go to the pulsair valves Inside the pulsair valve there is a stainless steel one way flapper that allows clean filtered air into the exhaust using back pressure every time an exhaust valve closes and prevents exhaust flow into the intake system The first sign of a failed pulsair valve is a cooked and cracked hose attached to the pulsair valves In my case the plastic valve with the small tube going to the pair valve did not fail There are no disks at the manifold or tubing the one way flapper disks are in the pulsair valves am not sure what causes the failure of the valve but think exhaust crud is a result of the valve failure The valve cannot be repaired Regina Air Temperature Sensor The Regina fuel injection system uses air pressure and temperature in the intake system to compute the air mass moving into the engine The temperature sensor is located in the intake hose or pipe The air mass passes through holes in the sensor and over a bulb which sends a temperature signal from the incoming air charge to the ECU Information from this sensor is added to the pressure sensor information to calculate the air mass being sent to the cylinders The sensor is an NTC Negative Temperature Coefficient thermister which means that resistance declines as the temperature increases This sensor helps the ECU to determine spark timing
23. dependent of the EGR system and many cars have both The pulsed secondary air injection solenoid or PAIR Solenoid file Cl Users Steve Documents Volvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors receives a signal from the ECU allowing the vacuum control valve to open via the small diameter tube to the plastic shut off valve The solenoid is located on the left strut support between the EGR Converter and the OBD box The shut off valve is located at the single end of the Y hose opposite the two pulsair valves The PAIR valve Pulsair valve with permission from the ECU allows oxygen in every time the exhaust valve closes which causes an instance of negative pressure the pulse and introduces oxygen into the manifold No air pump required The photo shows the two Pulsar valves feeding the exhaust manifold and a vacuum control valve which get its a signal from the PAIR solenoid to allow air from the air cleaner box to pass through If a valve fails it can allow exhaust gas flow back cooking the rubber hose The hose is connected to a vacuum operated shutoff valve connected to the air cleaner To test the pulsair valve on a cold engine place your hand over the valves near enough to verify that air is being taken in and exhaust gas is not escaping The action of the valve is a quick pulse corresponding to the opening and closing of the exhaust valves Also pull the hoses and look down to see the valves they shoul
24. dielectric grease EGR Valve Removal Procedure from Kevin The EGR intake tube is held to the intake manifold via 2 10mm bolts and a flange The exhaust side is screwed into the exhaust manifold with a 22mm acorn nut Once the tubes are separated the valve itself is held in a bracket via a large thin nut best removed with a large pliers found it took a good two handed pull to break the 22mm acorn nuts free the nuts that attach the pipes to the valve Your only option here is to use a 22mm open ended wrench unless you happen to have such a thing as a 22mm crows foot Be real careful not to have the wrench slip and round off the nut The valve gets hot in operation so the nuts tend to seize to the valve fittings and take some persuasion to break loose sprayed PBlaster penetrating oil on the fittings and let it sit for 20 minutes before trying This is a classic kKnuckle buster situation so it is a good idea to put on a pair of gloves Access is limited with a big wrench like this one but once the nuts are started you will be able to turn them 1 6 turn at a time till they are off Once the nuts were off had to tap the inlet pipe with a hammer to get it loose from the port on the end of the valve The compression fitting on the end of the pipe was kind of wedged in the port on the valve and did notwant to come off at first could not get the outlet pipe off of the side of the file Cl Users Steve Documents V olvo 20FAQ
25. e an approved type of electrical contact cleaner Squeeze dielectric grease into both sides of the connectors before re assembly 5 Charles Dinges Make sure the wiring feed to the knock sensor is not close to the alternator anecdotal reports of interference and retarded timing upon acceleration were solved by moving this wire Some electromagnetic interference from the alternator is the likely cause Electrical Sensor and Wiring Checks Note that testing at the ECU connectors requires the use of a multi meter and some skill in electronic electrical testing Accidents can be very expensive To avoid connector damage do not probe connectors from the end probe only from the sides or back When working with ECU modules and sensors always keep the ignition OFF KPO and disable power to the electronic unit by pulling all ECU fuses or disconnecting the battery except when required during testing This will help avoid accidental damage due to 1 At the ICU connector EZ116 K EZ117 K or Rexl ignition control unit check the wiring from the knock sensor 1 Remove the knock sensor connector 2 Remove the ICU connector and remove the shell to access the side of the connector for testing note the pin numbers stamped on the connector 3 Measure the resistance between ICU pin 12 and ground and between pin 13 and ground Both should be infinite open Anything else indicates damaged shorted wiring 4 Place a jumper wire at the knock senso
26. eft hand put your index finger on the top of the file Cl Users Steve Documents Volvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors retaining bolt grasp the sensor with your thumb and second finger and carefully maneuver the sensor into position lowering the sensor into the hole in the bell housing You may have to fiddle a bit but if you oriented yourself well before starting you ll find the hole easily with the part by feel Keep your index finger on the top of the retaining bolt as it rises when the sensor enters the bell housing Gently turn the assembly until you feel the retaining bolt find its threaded hole It s hard to describe but you ll feel it Very carefully move your hand and work with thumb and forefinger to start the bolt in the threads If you don t have lots of experience this will be the most difficult part of the job since the quarters are so tight and since you can t rotate the bolt much Don t rush and don t accidentally pull the bolt out and drop it The bracket is deep enough to keep the bolt from falling out on its own Just don t raise the bolt Once you ve started the threads with your left hand switch to your right hand thumb down and continue turning the bolt head to tighten it When you can no longer move it with your fingers use the ratchet box end of the wrench to finish the tightening job Broken Sensor Bracket Removal Editor The usual solution to a broken crank sensor br
27. en wire connected to the ECU get a pretty stable 52 volts which have read in the archives to be the ECU reference voltage Hopefully all is well at that end If connect the heater there is 13 5v on the harness side btw the sensor voltage decays over about 30 seconds to 01 volts At no time does voltage sweep from 3 to 7 v Also can you replace the heated one with non heated A Bosch Ford 5 litre sensor is 97 80 cdn at a local import autoparts store the Volvo sensor is 280 something Response 1 Abe Crombie That is the right resistance on the heater Use a digital voltmeter with impedance at least 10 megohm Before you replace the sensor warm up engine and attach the voltmeter positive probe to O2 sensor lead the green wire into pin 24 on the Fuel Injection ECU or using a sharp probe tip into the black sensor wire at the firewall connector the negative probe to a convenient chassis ground and leave the ozygen sensor connected Then turn on the engine and momentarily pinch the rubber return line behind fuel pressure regulator If the voltage of sensor goes to 7 9 V then look for something other than the sensor causing a lean condition A faulty sensor can give you the low V reading but an air leak or defective MAF sensor can do the same With regard to heated three wire versus non heated two wire yes and no The heated sensors are used to keep the signal active while idling Idling in cold weather primarily the sensor wil
28. en you just un screw it know this is trite but Re Assembly IS reverse order REALLY Tip In truly corroded cases heating the pipe or converter bung with an oxyacetylene torch should loosen the screwed in sensor Note from WBain Use an anti seize compound on the threads if the sensor did not come with any It will make any future disassembly easier Caution from David Hunter Also make sure you are not cross threading it easy to do on the O2 sensor Replacement Use of Generic Sensors Generics Editor You can install a generic Bosch or other three wire heated sensor instead of the more expensive Volvo OEM sensor in Bosch LH systems but you will have to splice in the connector The separate FAQ File on sensor replacements shows some wire length and splice information Bosch model numbers 13953 13942 and 13913 are reputed to work depending on your year and engine same sensor listed as for Ford 5 0 V8 Mustang engine but different harness lengths check the Bosch site for applications and see the FAQ File on sensor replacements Note See the table of generic replacements compiled by Brickboard members Note that several correspondents have noticed hesitation on acceleration after installing generic sensors due to peak voltages of 1 3 instead of 0 9 Replacing the sensor solved the problem OEM in 93 Bosch Frank In March of 1993 Volvo switched from a three wire O2 sensor to a four wire sensor The three wire generic s
29. engine bend the universal at 60 degree angle Pass the tool string behind the engine block There is a black cable that can be pushed out of the way The 3 extension and 10mm socket will align pretty easily with the top of the hex head machine screw Set the socket on the machine screw head Gently insert the ratchet into the extension string Turn gently to remove the machine screw Remove the tools Use your left hand to grip the sensor Using the Ratcheting Wrench Orient the wrench so that it will loosen the bolt and then using your left hand with your index finger placed over the ratcheting box insert your hand and the wrench carefully behind the engine block and place the racheting box end over the retaining bolt head The reason for putting your index finger over the box end is to make it easier to find that bolt head since you won t be able to see Carefully re orient your hand on the wrench trying not to pop the box end off the bolt head and then loosen the retaining bolt You ll be able to move the wrench only about 10 degrees so keep going until the ratchet won t loosen the retaining bolt any further then remove the wrench and your left hand Insert your right hand behind the engine block thumb down and use thumb and index finger to finish removing the retaining bolt Keep one finger on the bolt at all times You ll only be able to manage a partial turn each time When the bolt is free carefully remove it and take it out from the n
30. ensors are not interchangeable with the newer four wire applications Regina If you have a Regina equipped car use a sensor specifically engineered for Regina systems Regina cars through 1993 use a Volvo 394 sensor which is the same as NGK OTA4F B The Walker catalog lists 250 23811 as a direct fit replacement for Regina systems Note many aftermarket sites including FCPGroton do not distinguish between Bosch and Regina and claim that the Bosch unit fits all Not true To be sure buy the NGK unit for Regina which is listed at their website they confuse 8 and 16 valve cars but the correct Regina sensor is shown Installation Ken To install the generic sensor you will need to cut the wires on your harness and splice them to the sensor wire Crimping is recommended instead of soldering because solder weakens stranded wire subject to heat and vibration by decreasing its fatigue life The NGK website also recommends crimping using heat shrink tubing to protect the crimp Buy 3M crimp connectors with integral heat shrink tubing Walmart has these Do not use silicone dielectric grease on the connection since silicone contaminates the sensor Code 2 1 2 Faulty Oxygen Sensor in 960 Cars Rafael Riverol If the check file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors engine light on the dashboard lights up and you read OBD diagnostic code 2 1 2 faulty oxygen sensor
31. ex and cracked the electrical connection at the top of the sensor The answer all along was to remove the sensor s molded on electrical connector destroying the sensor and gain access to the hex with an offset 19mm box wrench or a 3 4 inch socket Jay Simkin Remove the old sensor and prep the new sensor by applying a thin coat of grease on the threads Then apply grey pipe joint compound not the white teflon loaded joint compound in a collar of compound on the underside of the sensor s lip above the threads Keep the joint compound away from the threads To reinstall gently screw the prepped sensor into the opening in the block Tighten snug using a 3 4 open end wrench A 3 4 socket will not work as the electrical connector housing is wider than the brass hex fitting used to secure the sensor Check for leaks Tighten gently if required to stop any leaks Replace the knock sensor using a 12mm wrench to tighten it securely file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors against the engine block Replace both electrical connectors and reconnect the battery negative Editor It helps to first remove assorted tubes and pipes including the IAC valve and the knock sensor nearby which is merely bolted into the block Engine Coolant Temperature Sensor Removing the Engine Coolant Temperature Sensor the rear most of the three sensors Volvo p n 1346030 or Bosch 0280130032
32. hat would coincide with a misfire Start by making sure any engine diagnostic codes are for real by resetting the trouble codes or disconnecting the battery and wait to see if they reappear Then do the physical and electrical checks below If all other tests check out you may want to swap in a known good knock sensor on spec Failing that an ICU swap may be in order Only in desperation should the FCU be swapped on spec Physical checks 1 Les Daniels One fault with these detectors is that the plastic housing cooks and then the detector basically falls to pieces 2 Check that the knock sensor on the block left side down below intake runners 2 and 3 is properly connected to the wiring harness It s easy to leave this connector off if you ve been working on the engine 3 Make sure the wiring connector for the knock sensor green with black or brown wire has not been accidentally switched with the block temp sensor connector red black with grey white wire The connectors are alike 4 Make sure all connections are making good contact straighten bent separated contacts check pins are fully seated by pushing in from back side Remember file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors to check the associated connector block at the strut tower or firewall Make sure all connections are clean and protected from oxidation Inspect for deteriorated damaged wiring Us
33. he same knock sensor offered in two interchangeable styles that may be used on the red engines Type 1 is on the left in the photo on the right and Type 2 on the right The only difference in the parts is the torque for the bolt holding the sensor to the block Type 1 has the flat top and the fastening bolt is torqued to 8 ft lbs 11Nm and Type 2 has the domed top and the fastening bolt is torqued to 15 ft lbs 20Nm If you use anti seize paste reduce the torque setting by 30 40 to account for the lubrication by the paste Operation nquiry How do test the knock sensor Response Abe Crombie If there is not a fault code for it then it is okay The ignition control unit tests it every time you exceed some thing around 3000 rpm with moderate to high throttle If it is not torqued properly it might not be as sensitive as it should or be overly sensitive Torque is 8 11 ft lbs It produces a high voltage pulse when it senses the shock wave in the range of combustion knock The voltage level iS proportional to the severity of the knock It will read 1 5 or greater megaohms but this is not really an effective test only the control unit detecting a sensor signal when the conditions would absolutely assure a Signal would be made is the real check The knock sensor test by whacking on block better than on the intake next to knock sensor see Duane s note below is only effective on early Chrysler systems with the throttle opened as the
34. hen reinstalling since they may interfere with temperature readings and with grounding against the block Better to use thin coat of a conductive grease such as OxGard or apply pipe joint compound above the threaded area Diagnosing ECT Failures Response Don Foster adapted to 700 900 series by Editor Your engine has two temp sensors one for the gauge it s mounted in the head about under intake header 2 and one for the FI it s mounted in the head about under intake header 3 The latter is the ECT sensor The sensor is an NTC thermistor negative temperature coefficient As the temp drops the resistance rises and as the temperature rises the resistance drops Thus if you have a broken wire defective sensor or bad connection I ve seen it happen the resistance measured by the ecu will be very high or infinite The ECU interprets this as minus a Zillion degrees and pours in the gas The car saw filled the oil with gas and certainly wouldn t run And the problem was only a displaced spade lug in the plastic connector housing According to file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors Chilton s you may choose to disregard this The coolant temperature signal to the control unit has a great influence on the computed injection period For example when the engine is being started and is cold the amount of injected fuel must be relatively large Editor Too ri
35. l fall below its 600F temp at which the reaction that makes it output voltage begins to work If it were to stay above this temp the non heated would be okay There are different sensors out there also Most all the Bosch up to 92 have the same output voltage at the same O2 gradient After 92 there are differences in some of the applications in this respect Regina vs Bosch Oxygen Sensors The Bendix Siemens Regina fuel injection systems use a titania type sensor which varies resistance and is not interchangeable with the Bosch zirconia units which create a varying voltage signal This sensor does not work with a 5 V reference out of the ECM as do the Bosch versions The Regina unit uses the heater power supply to feed a sensor circuit which responds to O2 level variations The Bosch zirconia unit measures an electrochemical reaction and the heater merely maintains the temperature stability of the sensor and does not supply current to be modified and used as output signal Compared to the more common zirconia O2 sensors titania sensors have three advantages 1 they don t need an air reference there is no internal venting to the outside atmosphere to plug up 2 they have a fast warm up time about 15 seconds and 3 they work at lower exhaust temperatures they won t cool off at idle and they can be located further downstream from the engine or used with turbochargers See the notes below regarding the use of generic sensors in Regin
36. le Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM Engine Sensors Removal of Bellhousing RPM Sensor Tips from Jay Simkin George Campbell and others The rpm sensor is awkward to access as it is below the cylinder head on top of bell housing It can be removed by using 21 of 1 4 or 3 8 extensions then a universal joint a 3 extension and a 10mm standard depth socket to turn the retaining 10mm hex head screw OR you can use a 10mm combination wrench with a racheting box end GearWrench Note that some cars use an 8mm bolt head Use a flashlight to locate the sensor and the bolt You ll have to peer at the thing from the passenger side fender looking over the air conditioning pipes It s below the distributor on the top of the bell housing Carefully put your left hand between the engine block and firewall and locate the retaining bolt head and the wire from the sensor with your fingers The reason for this is so you can orient yourself to its exact location While you re removing and replacing it you won t be able to see what you re doing so you ll need to visualize it in your mind Then clean the area around the sensor using brake cleaner and spray it with penetrating oil Using the Socket and Extensions to Loosen Without inserting the ratchet in the extension end pass the tools between the firewall and the aluminum colored air conditioning pipe Once the tools enter the space beside the
37. n perfect condition The cable and ends are pristine looking Is there a way to test it with a multimeter Response Ivan K To find the sensor stand at the left or drivers side front fender and look behind the rear of the cylinder head down towards the bell housing The crank sensor sits in a hole at the very top of the bell housing and has a black 1 4 inch diameter wiring harness leading into it down from the firewall harness Often these rpm sensors fail intermittently usually when hot This makes them hard to test Since the sensor is cheap enough just replace it With high mileage cars it s only a matter of time before they fail Response Measure the signal while the sensor is still installed by unplugging the sensor at the cable connections at the firewall to the drivers side of the engine Measure voltage here as the engine is being cranked Use a low voltage setting on a digital volt meter preferably in an alternating current setting if available in a low voltage setting If no signal is detected the unit is suspect The other simple measurement is to unplug the unit without removing it from its location behind the engine on top of the transmission housing Check all 3 terminals for resistance or an open circuit The new sensor measured about 160 ohms between the center lug and a side lug red and blue wires The black wire is the grounded shielding wire My old defective unit had no continuity and no measurable resistance fi
38. neSensors html 01 13 14 10 07 45 PM Engine Sensors go off Drive the car under light and heavy engine loads If diode flashes 4 times chech knock sensor wiring If wiring checks OK replace knock sensor and run above check again If diode continues to flash with road test you may have to replace the ignition control unit EGR Valve Service Requirements E i A LIN I I l TE Q Inquiry What exactly is the EGR It is specified in the service manual that it must be checked cleaned during the 90 000km 60000 mi service Response Tom Irwin The Exhaust Gas Recirculation EGR valve is located underneath the intake manifold If it gets plugged you can ruin an O2 sensor or get incorrect fuel metering basically the engine will run like crap and use a lot of gas To service the EGR it will be necessary to remove the air induction apparatus for clearance Removing the throttle body also helps and it is a good time to clean it out as well The same is true for the IAC Idle Air Contro EGR Valve valve Once you remove the EGR valve Take it to a bench and use a NTC later PTC EGR System Schematic vacuum pump to check operation and hold open the diaphragm and valve or follow the procedure below Spray carburetor cleaner through it Also spray into the tubes A stiff wire might be useful if there is large debris or a plugged line The temperature sensor electrical connector should be de oxidized and protected with silicone
39. r If it does not drop replace the sensor Problems may also occur in the sensor the vacuum tube leading to it the connector or the wiring leads OEM and Replacement Parts ACDelco makes these sensors with replacement parts as follows MAP sensor Volvo 3517892 146 ACDELCO Part 2131545 47 or GM Part 12569240 Volvo Maintenance FAQ for 7xx 9xx 90 Cars file Cl Users Steve Documents V olvo 20FAQ 20Updated EngineSensors html 01 13 14 10 07 45 PM
40. r connector between pins 1 and 2 5 Measure the resistance between ICU connector pins 12 and 13 It should be zero ohms Infinite resistance indicates an open wire or bad connector Anything else indicates a dirty connector 6 At the FCU connector LH 2 4 fuel injection control unit check the knock sensor signal from the ICU pin 4 Applies to EZ116 K ignition only 7 Remove the FCU connector and remove the shell to access the side of the connector for testing note the pin numbers stamped on the connector 8 Re install fuses Turn the ignition to ON KPII 9 Measure the voltage between FCU connector pin 28 and ground It should be approx 0 7 volts Anything else indicates a problem with the ICU or its wiring Sensor Testing Procedure Rafael Riverol Andreas Lofgren Connect test diode Volvo tool 5280 or LED from Radio Shack connected in series with 750 1500 ohm resistor which will work just as well for a couple of dollars black lead to connector on drivers side of the car wheel housing near steering fluid reservoir RED AND YELLOW LEAD Connect red lead of tool or LED to battery or ignition coil terminal 15 where you find 12V Use enough wire to run LED to passenger compartment or at least to hold it with windshield wiper where yoo can see while driving the car Turn ignition on and diode should stay lit Start the engine and run it about 900 rpm Diode should now file Cl Users Steve Documents V olvo 20FAQ 20Updated Engi
41. rial that acts like a galvanic battery electrolyte under certain SENSOR SIGNAL _ CIRCUIT conditions When the sensing element is cold the zirconia material behaves similar to an insulator At STREAM oi elevated temperatures the zirconia material performs ag gt Cie more like a semiconductor and can generate a Sas Wyctenen characteristic voltage output on the sensor connections ELECTROLYTE The outside of the bulb is exposed to the hot gases in the exhaust while the inside of the bulb is vented internally through the sensor body to the outside atmosphere Newer style O2 sensors breathe through their wire connectors and have no vent hole This is why grease should never be used on O2 sensor connectors because it can block the flow of air The difference in oxygen levels between the outside air and the exhaust within the sensor is what causes voltage to flow through the ceramic bulb The greater the difference the higher the voltage reading Typically an oxygen sensor will generate up to about 0 9 volts when the fuel mixture is rich and there is little unburned oxygen in the exhaust When the mixture is lean the sensor s output voltage will drop down to about 0 1 volts When the air fuel mixture is balanced or at the equilibrium point of about 14 7 to 1 the sensor will read around 45 volts When the computer receives a rich signal high voltage from the O2 sensor it leans the fuel mixture to reduce the sensor s reading
42. rify connector pins and wire colors When no knock sensor signal is detected the EZK ignition system defaults to full spark retard see also Engine Performance 1 OBD ignition trouble code 1 4 2 Missing signal from knock sensor 2 OBD fuel system trouble code 3 1 2 Missing knock sensor signal 3 The fuel system control unit FCU isn t getting the knock sensor signal from the ignition unit ICU at start up 4 Poor performance and acceleration due to excessively retarded timing 5 Over sensitive knock sensor possibly due to over torqued or failed knock sensor Cheap gas and heavily carboned engines may cause misfiring to the point that the knock sensor signal is not believed by the ECU Wiring and the knock sensor itself are by far the most common sources of knock sensor problems Les Daniels If this piezo detector fails it goes open circuit and the ECU thinks that a massive retarding of ignition called for hence the drop off in performance On carb models there can be backfiring as well Knock Sensor Testing The knock sensor can only be tested dynamically for proper waveform output with an oscilloscope Unless it makes you feel useful there is no point in tapping on the block to simulate knock sensor activity The voltage output of the piezoelectric quartz is too small and brief for normal measurement and furthermore the newer ignition systems won t be fooled into changing the timing as they selectively only detect knocking t
43. screw extractor into it then douse the thing with PBlaster penetrating oil and wait for it to work its magic The penetrant won t hurt anything like the clutch on the standard trans car On the other hand you want to avoid harming the timing ring on the automatic because it is not very strong You still run the risk of demolishing the bracket if you pry at it too hard so make sure you are patient and let any penetrant or silicone get in there before you pull it Once they move side to side they can gently be removed This sometimes takes a while but the rewards are that you don t have to pull the transmission On installation put a light coating of grease on the perimeter of the sensor where it contacts the bracket That will make your life a lot easier when you go to get it out of there next time And if you have the trans out for any reason take the RPM sensor out whether or not you reuse it and coat it LIGHTLY with a film of grease That will avoid the problem should the sensor need replacement in the future Editor Reinstallation George Campbell Don t bother trying to fish the new sensor s plug through there It s a waste of time Just zip tie the wire to the other wires after installation After plugging in and securing the new sensor carefully route it and let it drop behind the distributor near where it will go Coat the 10mm bolt threads and face with antiseize Insert the retaining bolt in the sensor s extension Using your l
44. t are not equipped with a ground wire must have a well grounded exhaust system to complete the sensing circuit Basic electrical wiring circuit checks should be made to determine if the vehicle s wiring harness has good continuity and is free from short circuits The ECU will set an O2 sensor diagnostic code if the sensor does not produce a voltage signal stays rich too long stays lean too long does not switch rich lean center too long or does not switch rich lean fast enough If the sensor dies altogether the result can be a fixed rich fuel mixture The rich mixture therefore can cause the converter to overheat resulting in severe damage and higher repair costs for the driver As one aftermarket manufacturer points out sensor checks come down to paying a little now or a lot later One way technicians can test oxygen sensors is to see if the sensor s output voltage changes when the fuel mixture changes When the mixture is lean the sensor s output voltage should be low down around 0 1 volts and when the mixture is rich the sensor s output should be high up around 0 9 volts A steady low voltage reading or no voltage reading would indicate a bad sensor Making the fuel mixture artificially rich by adding propane into the intake manifold should cause the sensor to respond almost immediately within 100 milliseconds and go to maximum 0 9v output On the other hand creating a lean mixture by opening a vacuum line should cause the sensor s
45. uldn t get the old sensor out of the hole into which it fits over the flywheel Where it s located makes it hard to get much of a grip on it tried rotating it in the hole to free it and then prying it up with a screwdriver To make a long story short it s not mounted in the beefy Volvo bell housing like thought but in a flimsy Fiat like aluminum casting that bolts into the back of the block And very easy to break I ve discovered And designed so you need to separate the bell housing from the engine to R amp R it Moral of the story is go easy on a stuck sensor Chris Herbst NEVER PRY the RPM sensor out of the bracket The poor quality bracket that they use to hold the sensor is SO weak that can break if you force the sensor around Prying side to side on the sensor can break either the bracket or the sensor leaving you helpless to do anything but pull the trans back to replace the bracket When you really pry that thing is usually when it breaks But because those brackets are so flimsy it can still get you when you don t expect it Usually 99 out of 100 is a piece of cake But when you re the one who has 100 it sucks Just be careful and you ll be fine Turn it lightly back and forth to remove it but don t force it at all Wait until it moves On a standard trans cars use a tiny bit of silicone spray to get the thing out and work it gently back and forth until it gradually loosens If it is an automatic get an Easy Out
46. ure Tip from Tom Haywood 95 960 B6304 with Motronic 1 8 the symptoms in my case were sudden very high idle surges 2500 3000 RPMs while sitting at idle and hot start problems This engine has two coolant sensors the rear coolant temperature sensor is Volvo 68 49 350 SWF 602 101 and apparently plays a role in fuel injection and various timing functions It is similar to the front one FRONT Volvo 35 45 031 but without the 5 inch connector wire Testing the sensor in heated water indicated normal operating ranges until reaching 180deg 220 ohms at which point the circuit would open completely infinite ohms When the brass housing would heat up it would pull the connector pin away from the thermistor leg have further learned that these symptoms can also point to the wiring to this sensor because of the location between the fire wall and hot engine parts could suggest to anyone with this engine to keep a new sensor handy because it looks like the car will be dead in the water when it fails This sensor is at the rear of the head and requires a mirror taped to the firewall and a 19mm open end wrench for removal drain the antifreeze and remove the heater hoses first Work from the top of the engine standing on a stepstool and using a pillow on which to kneel It has a 2 pin D type connector mounted right on the brass housing The large size of the connector keeps you from being able to get a good box end wrench on it but mine
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