Troubleshooting your TBI Fuel Injection System - 73
Contents
1. Replace Sensor Check voltage between harness terminal A and C with voltmeter Below 4 6 volts 4 6 Volts Check for open or short to brown wire Check for open or short to ground on connector Pin B orange wire ground on connector Pin C connector or ECM Circuit OK Faulty ECM Circuit OK Faulty ECM connector or ECM 44 Oxygen sensor lean Code 44 02 Lean Verify O2 Sensor is not unplugged If vehicle is equipped with a governor insure proper operation of the governor before using this chart Codes 33 and 34 can cause a code 44 codes are present repair them first before proceeding If either of these Sensor is not unplugged Ground diagnostic terminal field service mode Run warmed up engine for approximately 1 minute between 1200 and 1800 RPM note Check Engine Light Flashing Closed Loop Trouble Is intermittent Light staying off more than on or flashing Open Loop at either RPM Ignition off diagnostic terminal grounded Disconnect O2 sensor Start engine and note Check Engine Light at least 15 seconds Check Engine light off for Check Engine Light Flashing Open Loop Check Purple wire from ECM Pin D 7 for open or short to ground If cir2. Verify Sensor is not unplugged With a ohmmeter verify continuity between Pin C 10 and the ECT Sensor Sensor is not unplugged Clear code and verify that the code still sets before moving on with diagnostics if any actions were taken Engine off Clear codes Disconnect Coolant sensor and jumper harness terminals together Start engine and run until check engine light comes on Gound diagnostic connector and note code Cod e15 Code 14 Probe coolant sensor harness yellow wire with a voltmeter to ground Should measure 4 6 volts Faulty coolant sensor or connection 4 6 volts Below 4 volts Ignition off disconnect ECM connector C D Check yellow wire C 10 for open circuit If no open circuit it is faulty ECM or ECM connector ECM connector Ignition off disconnect ECM connector C D Check yellow wire C 10 for open circuit If no open circuit it is faulty ECM or 21 High voltage at throttle positon sensor Sensor could be unplugged Code 21 TPS High Verify Sensor is not unplugged With an ohmmeter verify continuity between Pin C 13 and Pin B flat TPS or Pin C round TPS on the TP Sensor Engine off Clear codes Start engine and run until check engine light comes on Gound diagnostic connector and note code
3. Sensor is not unplugged Clear code and verify that the code still sets before moving on with diagnostics if any actions were taken Cod e21 No Code set problem is intermittent Clear codes Disconnect TP Sensor Start engine and idle till CE light comes on Note the code that is set Key on engine off Backprobe with voltmeter between Pin B flat TPS or Pin C round TPS and ground Manually move throttle slowly from closed to WOT Insure that voltmeter increases in voltage and does not glitch open or closed during the process If there are Code 22 any disruptions replace sensor If OK check connections and connector aa Code 21 Probe TPS Harness pin A flat TPS or Pin B round TPS with test light to 12 Check Pin B flat TPS or Pin C round TPS for short to other voltage Check for short to pin C flat TPS or Pin A If all OK ECM could be at fault volts Light ON round TPS Light Off Faulty TPS Repair open in Blk wht wire connection or Pin A flat TPS Pin B round Sensor TPS 22 Low voltage at throttle position sensor Code 22 TPS Low Verify Sensor is not unplugged With an ohmmeter verify contin Pin C round TPS on the TP Sensor uity between Pin C 13 and Pin B flat TPS or Sensor
4. OK go to b b Check voltage at check engine light if 12 volt are not present the check engine light is not connected properly If 12 volts are present either the ECM is not powered properly or is defective 1 Insure that the IGN1 wire is not connected to a battery feed a Check pink wire to the power relay and or the pink wire powering up the injector s to insure there is no voltage with the key off If voltage is present with the key off the pink wire is not properly connected or the power relay is bad b Check fuel pump relay for proper operation e Turn ignition off for at least 15 seconds e Connect voltmeter or test light to the blue wire at the fuel pump relay e Turn ignition on voltage should be present at this wire for the first 2 or 3 seconds after turning on the ignition switch e If voltage is not present either the ECM is not powered or grounded properly or the ECM is faulty e If voltage is present check for voltage at the fuel pump with the same type of operation e If voltage is not present at the fuel pump check the wiring if wires appear to be OK replace the fuel pump relay e f voltage is present verify the ground for the fuel pump is sufficient and securely fastened If fuel pump ground is OK the fuel pump is defective If you have gone through all of the above procedures and the fuel pump is still not coming on when you turn the key on you will need to call tech support When you call tech support you will nee
5. TO BLOCK GROUND TOTAL CONNECT WD 1 D 6 B 1 BAT RED FUSED CONNECTS WITH C 16 B 2 ORANGE FUEL PUMP RELAY PIN A B 3 BLACK WHITE PIN D DIST GROUND W SMALL DIST PIN A B 5 TAN PINB DIST REF W SMALL DIST PIN C B 7 WHITE 60 ESC PINC PIND GND PINBING PINE KNOCK SEN if equipped B 8 GREEN A C or Compressor Winch idle increase B 10 P N 4 C 3 GREEN IAC W MALE WP PIN D C 4 BLUE IAC W MALE W P PIN C C 5 GREEN IAC W MALE W P PIN A C 6 BLUE IAC W MALE W P PINB C 7 GREEN HIGH GEAR C 9 TAN CRANK INPUT TO STARTER STUD or IGNITION SWITCH C 10 YELLOW ECT C 11 BROWN MAP INPUT PIN B ON GREEN CON C 12 TAN MAT if equipped C 13 BROWN TPS PIN B ROUND TPS PIN C C 14 ORANGE 5V REF GOES TO MAP amp TPS PIN C ROUND TPS PIN A C 16 RED 12 VOLT CONNECTS IN WITH B 1 gt A D 1 BLACK BLOCK GROUND CONNECT W D 6 A 12 D 2 BLACK WHITE ECT amp TPS RETURN ON TPS PIN A ROUND TPS PIN B D 4 TAN DIST SIGNAL PIN A W SMALL DIST PIN D D 5 BLUE IGN BYPASS FOR TIMMING PIN C W SMALL DIST PIN B D 6 BLACK WHITE 0 2 GROUND GOES TO BLOCK GROUND CONNECT W D 1 A 12 D 7 PURPLE 0 2 D 14 GREEN INJECTOR S PIN B D 16 PURPLE INJECTOR S PIN B PINK WIRE TO IGN 1 PIN A FROM INJECTORS FROM A6 PIN D ON FUEL PUMP RELAY TO BLOCK GROUND 28 BLACK PIN E ON FUEL PUMP RELAY TO IGN PIN A ON ALDL TO BLOCK GROUND RELAY 85 FROM ING SWITCH 30 86 GROUND 85 87A 86 30 12V ALSO CONNECT W 12V TO ECM B1 C16 87 87 ING OUT PIN A FOR SMALL DIST 2 PIN CONN IS IGN PIN B IS
6. at hand 4 do not seem to have as much power as I should Verify that you have set your timing properly by disconnecting the set timing connector setting the timing to the specified value reconnecting the connector and shutting the engine off and starting it back up before proceeding For tach filter applications insure that the timing is set to factory specifications and that both the mechanical and vacuum advance units are operating properly In some instances you can advance your timing an additional 4 5 degrees and evaluate If you do not have any spark knock this setting may be OK for your application Evaluate for spark knock and return the ignition timing back to its base at any time you may encounter spark knock Ensure that your plug wires are properly connected with the correct firing order Your fuel pressure may be insufficient see fuel system checks at the beginning of this guide Verify that there are no vacuum leaks and that the MAP sensor is properly connected 5 am getting a sag when I accelerate Timing is a critical issue with sags Verify that your timing is correctly set by disconnecting the set timing connector and properly setting the timing see 4 also Fuel pressure is not adequate for proper operation make sure that there is no contamination in the tank or your fuel filter is plugged See Fuel System check above A plugged fuel filter may be an indication of a contaminated tank Bad ground to the blo
7. position voltage check between the brown wire and the black white striped wire on the TPS with the TPS still connected and the key on DO NOT PUNCTURE THE WIRES to measure this voltage and only use a digital voltmeter Voltage can be measured by back probing the TPS connector between these wires either with a thin paper clip or appropriate tool used for this type of measurement If you have gone through all of the above procedures and the engine still will not start you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available Fuel pressure at the inlet of the TBI unit Return line fuel pressure Codes stored in the ECM Any information that you feel is important for diagnosing the issue at hand 2 My engine is running to lean or is backfiring on acceleration Assumption here is that all plug wires are installed properly the secondary ignition system plug wires coil cap and rotor is in good operating order and the engine is in good order Perform fuel system checks found at the beginning of this guide Check initial ignition timing again If the timing is OK check to insure that the timing is advancing as it should with throttle lever actuation If the fuel system checks performed are OK and the initial ignition timing is OK we may not have been given the proper info
8. terminal of the coil for external coil applications or to the positive slot for coil in cap applications Remove plug wire and check for spark while cranking No Spark Repair ignition system Has spark Insure wire continuity between the ECM and the distributor or tach Filter If fuel is still not spraying go to fuel system troubleshooting before replacing any components If all wires are in tact and routed correctly and all fuel system checks are correct replace distributor module or tach filter 2 Perform the fuel system checks found at the beginning of this troubleshooting Guide If the fuel pressure and fuel system are operating as required Insure that the check engine light is on with the key on but the engine not running and there are no stored codes except for code 42 if you have just set the ignition timing or code 12 If you have installed a new distributor removed the distributor for any reason your ignition timing may be off too much to operate the engine properly Disconnect the connector s from the injectors and set the ignition timing to its proper setting while cranking the engine Assumption here also is that the timing mark on the balancer is lined up with TDC of 1 cylinder and that the distributor is seated properly and not 180 degrees off If all of this checks OK go to step 3 3 Measure the voltage on the throttle position sensor If using a scan tool you can read TPS if not measure the voltage To measure the throttle
9. the crank side of the starter solenoid Check that the MAP sensor is properly connected to a full manifold vacuum source Ensure that the vacuum source to your MAP sensor is free from restrictions and has a secure connection Throttle plates are not adjusted properly not allowing an adequate amount of air for starting the engine Go to Troubleshooting guide 10 and verify the adjustment Throttle position sensor is out of adjustment or faulty Throttle position voltage with throttle fully closed with the key on should be 5 volts 2 volts If you have gone through all of the above procedures and the engine is still sagging on acceleration you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available IAC counts at stabilized idle in drive if using a scan tool Engine operational temperature Initial ignition timing Any information that you feel is important for diagnosing the issue at hand 7 The fuel pump is not coming on when first turn the key on Is the check engine light on with the key on engine off Assumes check engine light is connected properly see installation instructions to verify check engine light installation Yes Go to step 1 No Check for proper installation of check engine light a Check fuses to insure that they are not blown If fuses are
10. well to use your stereo again A better place to remove power is at the fuse TROUBLE CODES 12 No reference pulses to Electronic Control Module ECM The code is always flashed when checking codes and only indicates that the engine is not running 13 Oxygen sensor signal stays lean during warm engine cruise your O2 sensor could be unplugged Code 13 02 open Verify Sensor is not unplugged With a voltmeter verify continuity between Pin D 7 and the O2 Sensor With an ohmmeter verify continuity from ground to Pin D 6 Sensor is not unplugged Signal and ground wire both have continuity moving on with diagnostics kk Service diagnostic mode Clear code and verify that the code still sets before With engine fully warmed up Place the engine into Flashes Closed Loop Problem is Intermittent Check for chaffed or loose wires O2 sensor may be bad Flashes Open Loop Turn engine off Diagnostic terminal grounded still Unplug O2 sensor and ground connector terminal Start engine and im note check engine light mediately Check engine light went out for at least 15 seconds Faulty connector or sensor Check engine light fl ashing Open Loop Check for opens in the circuits just as above If no opens exist then you have a faulty ECM connecto
11. COIL WIRE WHITE
12. Troubleshooting your TBI Fuel Injection System Most of the problems encountered while installing your fuel injection system or after a time of operation are very simple If your check engine light is on you more than likely have a hard fault meaning something is grounded out unplugged operating out of range or has gone bad See below for how to determine what your fault may be and what the codes mean With the addition of Fuel Injection to your engine it is important to remember that the basics are still there necessary and have not changed Batteries must be fully charged charging systems fully operational the ignition system is fully operational and the integrity of the engine is intact All of these items are common to an engine and need to be in full operational condition regardless of the fuel system that has been added to your engine The ALDL connector allows for full diagnostics of your unit A scan tool can be used and set up for a GM TBI application to read the data or to check for stored codes Consult a service manual or see below for any check engine light code definitions You can use a late 80 s or early 90 s GM TBI definition If you have access to a scan tool use a hook up for a 1990 350 cu in 5 7L Chevrolet truck For some scan tools enter VIN 10 L 3 c 8h K If you have installed a Fuel Injection system in your vehicle and are having some initial issues here is a quick checklist to work from to get you s
13. ck insure that the surface that you are making the connection to on the block is clean and making a positive connection Your O2 sensor may be contaminated bad or not properly installed in the exhaust You may have left out some of the important specifications for the proper calibration chip to be made If you have gone through all of the above procedures and the engine is still Sagging on acceleration you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available Return line fuel pressure Voltage measured at the battery while running Voltage measured at the pink wire on the injector while cranking Engine RPM at start up idle on a cold start ___ 2222222 Engine RPM at idle with stabilized temperature Engine operational temperature Initial ignition timing Any information that you feel is important for diagnosing the issue at hand 6 My engine takes longer to start than I think it should Check for vacuum leaks this is the most common cause Make sure that your timing is set correctly see Troubleshooting point 4 Fuel pressure is not adequate for proper operation See Fuel System Checks at the beginning of this guide Fuel pump relay is not coming on or is faulty On a TBI system verify that the crank wire is connected to the crank side of the ignition switch or
14. cuit and wire OK Faulty ECM or ECM connector Check the following Sensors Bad or lean injectors Contaminated fuel EGR valve if equipped Low fuel pressure Vacuum leaks or exhaust system leaks If all check OK replace O2 sensor Service diagnostic mode is entered the same as Engine Off Self Test Ground out Pin A and B on the ALDL connector with the engine running Rapid flashing approx 1 2 1 sec interval is open loop Flashing at a slower rate indicates closed loop 45 Oxygen sensor rich Code 45 02 Rich Verify O2 Sensor is not unplugged If vehicle is equipped with a governor insure proper operation of the governor before using this chart Codes 33 and 34 can cause a code 45 If either of these codes are present repair them first before proceeding Sensor is not unplugged Ground diagnostic terminal field service mode Run warmed up engine for approximately 1 minute between 1200 and 1800 RPM note Check Engine Light Flashing Closed Loop Light staying on more than off or flashing Open Loop Trouble is intermittent perform fuel system check contaminated O2 sensor Ignition off diagnostic terminal grounded or other forms of non metered fuel Disconnect O2 sensor and ground harness end of connector Start engine and note Check Engine Light Check Engin
15. d to have the following information available Voltage measured with voltmeter between the black wire and pink wire on the fuel pump for the first 3 seconds of the keyon Any information that you feel is important for diagnosing the issue at hand 8 The RPM on my engine does not come down when come to an idle e More than likely you have a large vacuum leak verify that your system is free from vacuum leaks e Check that all non used vacuum ports are plugged e Verify that the bolts holding down your throttle body are not protruding through the bottom of the adapter plate causing the plate to lift off its base e Your ignition wire is connected to a battery source and not an ignition 1 source e The engine has not come to full operating temperature as of yet e Your thermostat is inoperable or opens at too low of a temperature You should be using at least a 180 stat e Throttle cable or throttle on the throttle body is not coming to a complete close Throttle plate is binding in the throttle bores e The throttle plates are adjusted too far out see procedure 10 for proper adjustment sequence e IAC is not working either faulty or there is a wiring issue If you have gone through all of the above procedures and the engine is still idling too high you will need to call tech support When you call tech support you will need to have the following information available Voltage measured between the black wire and brown wire on th
16. e fresh air hole that the IAC receives its air from f If you do not have a fast idle then it is OK and you can proceed to adjust the throttle plates Let the engine idle for a little bit and then check you idle speed The speed should be about 575 600 at idle in drive or about 50 rpm less than you requested for your chip If it is lower than this you can raise the idle up or if it is above this determine if you should bring the speed down More than likely it will always be lower g There is a little cap on the side of the throttle body by your throttle lever that has an adjustment screw under it if not already removed h Remove this cap and use the screw under there to adjust your base idle speed without the IAC operational Base idle is to be set in drive for an automatic transmission i If you have done all of this and you still have an issue we may not have received all of the proper information to build your chip and you will need to call tech support If you have gone through all of the above procedures and the engine is still idling too high you will need to call tech support When you call tech support you will need to have the following information available Voltage measured between the black wire and brown wire on the TPS with the key on engine not Any information that you feel is important for diagnosing the issue at hand 11 My fuel pump is real noisy If your fuel pump is real noisy you may not have isolated it from the bod
17. e light off for at least 30 seconds Steady Light System is Rich Faulty ECM Check the following Sensors Bad or leaking injectors Contaminated fuel EGR valve if equipped High fuel pressure Performfuel system check out Service diagnostic mode is entered the same as Engine Off Self Test Ground out Pin A and B on the ALDL connector with the engine running Rapid flashing approx 1 2 1 sec interval is open loop Flashing at a slower rate indicates closed loop 51 PROM error 52 Calpak Missing 54 Low voltage at fuel pump OR Low voltage at Fuel pump relay 55 Problem at Electronic Control Module ECM ECM failure OR Serial bus error Code 51 Eprom Problem Check that all pins are fully inserted in the socket If OK replace PROM clear memory and recheck If code 51 reappears replace ECM PR cere eae Code 52 Fuel CALPAK missing Install missing or faulty CALPAK Code 54 Fuel Pump Relay or relay wiring Code 55 Replace ECM FUEL INJECTION T B I WIRE PINOUT A 1 BLUE FUEL PUMP RELAY F A 4 WHITE EGR if equipped A 5 ORANGE CHECK ENGINE LITE A 6 PINK IGN 1 RUN TO PIN A ON INJECTORS A 7 PURPLE TOURQUE CONVERTER if equipped A 8 BLUE ALDL CON PIN E A 9 BROWN ALDL CON PIN B A 10 BROWN VEHICLE SPEED SENSOR A 11 BLACK WHITE MAP RETURN GREEN CON A A 12 BLACK
18. e TPS with the key on engine not Engine operational temperature Initial ignition timing 2222 Any information that you feel is important for diagnosing the issue at hand 9 am not getting as good of fuel economy as think should If all is set up properly with the installation of your fuel injection system you are probably getting as good of fuel economy as you are going to get 1 Insure that your timing is set properly 2 Your thermostat is in good working order 3 Your fuel pressure is at the specified pressure see fuel system check at the beginning of this guide 4 You may have other factors such as tires brake drag or other external issue from the fuel injection system that is not working properly 5 Re evaluate your driving habits and insure that you are driving in a fashion that will provide you optimum fuel economy If you are trying to race everyone from the light chances are you will not get the fuel economy that you expect If you have gone through all of the above procedures and you still feel that you should be getting better fuel economy you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available Voltage measured between the black wire and brown wire on the TPS with the key on engine not Any information that you feel is important for diagnosing the is
19. fuel pressure Fuel pressure should be a constant 10 15 PSI on a TBI fuel injection system and is typically around 12 13 psi Higher pressure than 15 psi indicates that there is an issue with the installation Many times this is due to kinked fuel lines improper routing of the return line and or fuel line restrictions See Part 3 of Troubleshooting guide 3 Many fuel tanks have fittings on them which are used for a fuel tank vent These fittings are not suitable to use as a return line because they have an orifice in them and restrict the flow of fuel back to the tank If you have installed your return line to a vent line you will need to route the return line in a different fashion Fuel pressure on a TBI unit should stay constant under all throttle conditions There should be less than 1 psi of pressure difference from idle to WOT operation of the TBI unit A pressure drop of more than 1 psi under these conditions indicates an issue with the fuel delivery system With retrofit fuel injection systems many times we are drawing fuel from gas tanks that are many years old hence many years have passed where contamination can settle into the fuel tank The electric fuel pump installed for a fuel injection system will draw considerable more volume of fuel from your tank than your old system did If there are any contaminants in the tank this many times will plug up or greatly restrict the flow of fuel to the system causing many issues Step by S
20. ge sucking sound coming from the throttle body when it is warmed up My engine stalls or almost stalls when come down to an idle 11 My fuel pump is real noisy 12 My check engine light does not come on when I turn the key on 13 My check engine light is flashing fast all the time 14 My check engine light is on when the engine is running 1 Engine cranks but will not start There is an assumption that the battery is at a full state of charge the fuel tank has fuel in it and that all sensors are correctly connected and there are no trouble codes in the ECM 1 Does the injector spray fuel when cranking the engine Yes Go to step 2 No Remove one of the injector connectors from an injector With a voltmeter or test light measure the voltage or validate power to the pink wire of the connector with the key on Yes Pink wire has voltage go to step 1a No There is no power getting to the system Check for proper connection to the battery fuses are good relays have been connected and seated properly Correct the power issue if there is still no fuel spray when cranking the engine after this has been corrected go to step la la With the voltmeter or test light still connected crank the engine and verify voltage to the pink wire on the injector connector Results 0 volts or the light goes out when cranking the engine The primary pink ignition wire is incorrectly connected to the vehicle This is to be an ign
21. is not unplugged Clear code and verify that the code still sets before moving on with diagnostics if any actions were taken Start engine and run Engine off Clear codes until check engine light comes on Gound diagnostic connector and note code Code 22 Clear codes Disconnect TP Sensor and jumper pin C to B flat TPS or Pin A to C round TPS Start engine and idle till CE light comes on Note the code that is set Code 22 No Code set problem is intermittent connector Key on engine off Backprobe with voltmeter between Pin B flat TPS or Pin C round TPS and ground Manually move throttle slowly from closed to WOT Insure that voltmeter increases in voltage and does not glitch open or closed during the process If there are any disruptions replace sensor If OK check connections and Code Remove Jumper from pins 21 Check voltage between Pin C and A flat TPS or Pin A and B round TPS Replace TPS 4 6 volts Below 4 volts Disconnect ECM connector and check for open or short to ground in TPS signal brown wire If OK it is faulty ECM connector terminal or ECM Disconnect ECM connector and check for open or short to ground in 5v signal orange wire If OK it is faulty ECM connector terminal or ECM 33 High
22. ition 1 ING1 source which is power in both the key run and crank position Correct the connection of this wire and verify voltage to the pink wire on the injector connector Test again for fuel spray during crank If the engine still cranks is spraying fuel but will not start go to step 2 Low volts lt 8 This is an indication of either a battery in a state of very low charge a bad battery or too much resistance in the system record the battery voltage while cranking at the battery record the voltage at the pink wire of the injector connector while cranking the engine compare these two voltages they should be within 2 2 10 volts of each other If these voltages are greater than 2 there is a bad connection or too much resistance in the wire feeding the ECM Correct the issue with low voltage If cranking voltage is above 9 volts while cranking and there is still no fuel spraying the issue is in the fuel delivery system 9 volts or higher this is normal cranking voltage If there is no fuel spraying while cranking the issue is in the fuel delivery system or ignition system Trouble shoot the fuel system for improper operation See Fuel System checks at the beginning of this guide Troubleshoot ignition system go to 1b 1b Your TBI fuel injection system fueling is triggered from the ignition system It is assumed that the coil is operational a 12 volt ignition 1 IGN1 source is connected to the positive
23. memory area of the ECM and follow the diagnostic procedures for that particular code If you have a scan tool this is very easy If you do not have a scan tool you can use your check engine light to output the fault codes Below you will find this procedure along with a definition of all the different fault codes that can be output THE CONNECTOR tab IM L K JT To Display Trouble Codes Run a wire I use a paper clip that is in a U from Pin A to Pin B with the ignition on but the engine not running The Check Engine light will flash in the following sequence flash pause flash flash long pause flash pause flash flash long pause flash pause flash flash long pause This is a code 12 which will always be there After this series of flashes and pauses any stored trouble codes will now flash If you do not see the 12 flash three times your diagnostic circuit is defective Vehicles will display stored trouble codes then 12 again followed by energizing most system controlled relays The fuel pump relay will not energize The idle air control valve will fully extend to enable checking minimum idle speed CLEARING THE TROUBLE CODES Turn the keyswitch to the off position To clear any trouble codes disconnect the battery for 30 seconds or unplug the connectors to the ECM If this is done at the battery and your car stereo is equipped and programmed with a four digit pin code you may have to re enter that as
24. ose is OK check for open ground circuit in blk wht wire pin A If ground circuit is OK Replace sensor 34 Low voltage high vacuum at MAP sensor Code 34 MAP Low Verify Sensor is not unplugged If vehicle is equipped with a governor insure proper operation of the governor before using this chart If engine idle is rough unstable or incorrect correct any issues before using this chart Sensor is not unplugged Clear code and verify that the code still sets before moving on with diagnostics if any actions were taken Engine off Clear codes Start engine and run until check engine light comes on Gound diagnostic connector and note code Code 34 No Code set problem is intermittent Clear codes Disconnect sensor and jumper harness terminal B to C and run engine for 1 minute or until CE light comes Key on engine off Backprobe with voltmeter between Pin B and Pin A With no vacuum applied voltage should be over 4 volts Apply 25 of vacuum with a hand held or similar vacuum pump Voltage should be approx 1 1 5 on volts If these voltages are correct system is working as it Note the code that is set should Look for loose or chaffed wires terminals or connectors See first note on idle conditions Check TPS Code 34 adjustment Code 33 Remove jumper B to C
25. r or ECM Service diagnostic mode is entered the same as Engine Off Self Test Ground out Pin A and B on the ALDL connector with the engine running Rapid flashing approx 1 2 1 sec interval is open loop Flashing at a slower rate indicates closed loop 14 High temperature indicated at engine coolant temp sensor Sensor could be unplugged Code 14 Coolant Sensor Low Verify Sensor is not unplugged With a ohmmeter verify continuity between Pin C 10 and the ECT Sensor Sensor is not unplugged taken wire and ground Clear code and verify that the code still sets before moving on with diagnostics if any actions were With engine fully warmed up unplug ECT sensor and check voltage between ECT connector yellow Over 4 volts Check resistance across sensor resistance should be more than 100 ohms Below 4 volts If all wiring checks out OK above the problem is the ECM or ECM connector If resistance is above 100 ohms the problem is intermittent Verify that all wiring is OK and not chaffed or grounding out Disconnect ECM connector and insure yellow wire to Pin C 10 is not grounded out to the chassis or another wire Resistance is below 100 ohms replace sensor 15 Low temperature indicated at engine coolant temp sensor High Code 15 Coolant Sensor
26. ressure measured at 12 psi or 1 psi while running Yes If the engine is still running rich go to step 4 No Is the return line connected to an unrestricted return port on the fuel tank Many fuel tanks have a port on the fuel tank that is for a fuel vent These ports are not adequate for a fuel return There is an orifice in these ports that will restrict the flow of fuel Check that you have not used a vent port for the fuel return line No Go to step 3a Yes Fuel is being returned to a vent line Re route fuel return line to a non orificed port or fabricate a free flowing return line port to the fuel tank or fuel return If still running rich go to step 3a 3a Measure return line fuel pressure This pressure should be less than 3 psi if not there is a restriction in the return fuel line If return fuel line pressure is less than 3 psi and the engine is still running rich go to step 4 If return line pressure is not less than 3 psi there is a restriction in the fuel line Find and repair the restriction until the fuel pressure on the return line is less than 3psi In some cases this requires a larger diameter fuel return line Go to step 3b to help determine root cause of increased return line pressure 3b Remove the fuel return line and attach a length of rubber hose of sufficient length to run into an approved gasoline container Run engine and recheck fuel pressure on both the feed side and the return side If both
27. ressure to the system Fuel Pressure is critical for proper operation Fuel tank must be free from debris and fuel pressure needs to be constant and consistent Some aftermarket high density fuel filters can cause a large drop in fuel pressure under load and are not recommended for use with your system If you are using one of these types of filters insure that you have proper fuel pressure during all modes of operation 99 of all issues are usually taken care of with one or more of these 8 steps of diagnosis First and foremost the engine and fuel injection system must be free from vacuum leaks Vacuum leaks are the leading cause of installation issues with your fuel injection system Check all sources of potential vacuum leaks including components not related to the fuel injection system There are instances where the vacuum leak is coming from the adapter plate used to attach the throttle body to the manifold If this is the case make sure that the seal is positive between the manifold and the adapter plate also between the adapter plate and the throttle body In some instances it is necessary to seal these with silicone to provide a positive seal Another common issue is a lack of good grounding Many issues have been resolved simply by making sure that the ground path is secure and clean Fuel System Checks Fuel Pressure is critical to the operation of a fuel injection system Always check to insure that you have the proper
28. rmation to build your system and you will need to call tech support If you have gone through all of the above procedures and the engine is still running lean or is backfiring on acceleration you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available Engine operational temperature Initial ignition timing Timing at 2000 RPM____ Any information that you feel is important for diagnosing the issue at hand 3 Engine runs too rich Check for vacuum leaks and insure that all vacuum leaks are corrected and sealed If the engine is also running at a higher than expected idle this is a good indication of a vacuum leak as well 1 Is the vacuum line to the MAP sensor securely fastened to both the MAP sensor port and the port on the throttle body Yes If engine is still running rich go to step 2 No Repair leak kink or routing is engine still running rich If yes go to step 2 2 Is the MAP sensor connected to a full manifold vacuum port For 2 bbl units this will be the port on the back of the throttle body between the two fuel lines or the far left port on the front side of the throttle body as you are looking at the Yes If engine is still running rich go to step 3 No Correct the vacuum source issue if the engine is still running rich go to step 3 3 Is the fuel p
29. sides are within the above ranges there is a restriction in the fuel delivery system that needs to be repaired 4 Does the engine have a fully operational thermostat Yes insure that the engine will reach 180 deg in a reasonable time go to step 5 No Install new thermostat proper size thermostat will be 180 or higher 160 degree in many cases is OK but the preference is 180 or higher If still running rich go to step 5 5 Is the coolant sensor installed in a portion of the engine or the cylinder block which provides a constant flow of coolant over the tip of the sensor Yes Go to step 6 No Reinstall the coolant sensor in a different location to insure constant flow of coolant over the sensor If still running rich go to step 6 6 Is the charging system operating properly and is the voltage measured at the battery and the injector 13 volts or higher with the engine running Yes Go to step 7 No Repair charging system Note the discussion about older style AC Delco single wire alternators If still running rich after reparing go to step 7 7 If you have gone through all of the above procedures and the engine is still running rich you will need to call tech support In many cases the specifications of the engine are different than what was originally discussed or assumed When you call tech support you will need to have the following information available Any information that you feel is important for diagnosing the issue
30. sue at hand 10 The engine is revving up and down when come down to an idle There is a large sucking sound coming from the throttle body when it is warmed up My engine stalls or almost stalls when come down to an idle This is usually an indication of a vacuum leak again make sure that you have no vacuum leaks This could also be an indication of the wrong base ignition timing Verify that you have set your ignition timing correctly see 4 Your engine may also require more air going through the throttle plates at idle than it is currently set for Here is a procedure to check this setting a Make sure your engine temperature is at full operating temperature b Jumper Pins A amp B of the ALDL connector I use a paper clip with the key on but the engine off This is the same thing you do when checking for engine codes and your check engine light will flash off and on c Wait about 45 seconds or until any trouble codes present have flashed through code 12 is normal see 14 After this then unplug your IAC valve which is on the throttle body but do not turn off the key d Remove the jumper from the ALDL turn the key off wait 15 seconds and start the engine It may start hard and you may have to depress the throttle pedal a little bit to start the engine e If you have a fast idle this did not work or you have a vacuum leak that is not repaired or the throttle plates are already too far open You may have to tape over th
31. tarted Pink Ignition wire MUST be connected to 12 volt switched ignition that receives power during crank and key on 1 Check to make sure your check engine light is not on or that it is on with the key on but the engine is not running 2 Make sure that the red battery wire is connected to a battery source It is highly recommended that this wire is connected directly to the battery and the pink wire is connected to an ignition 1 source If your ignition wire is not connected to an ignition 1 source your ECM will not be powered while cranking the engine 3 Check that the ground wire is securely fastened to the block and that the interface between the block and the terminal are clean 4 Ensure that there are NO vacuum leaks 5 Ensure that your MAP sensor is connected to a full manifold vacuum source and not a ported source 6 Set the ignition timing correctly making sure that you disconnect the set timing connector to set it In some cases you cannot set the timing with the connector disconnected and keep the engine running If this happens set timing to 15 degrees allow the engine to fully warm up then disconnect the set timing connector to set the base timing to the correct specification 7 Ensure that you have full manifold vacuum routed to your fuel pressure regulator if equipped on MPFI systems and there are no vacuum leaks with this connection 8 Check your fuel pressure to ensure that you are providing the proper p
32. ted see wiring diagram provided If you are not receiving 12 volts to the ECM something in the vehicle s power circuit is not connected properly d If 12 volts is available at the proper cavities of the ECM please check that you have a proper ground circuit to the engine block If you have gone through all of the above procedures and the fuel pump is still not coming on when you turn the key on you will need to call tech support When you call tech support you will need to have the following information available Any information that you feel is important for diagnosing the issue at hand 13 My check engine light is flashing fast all the time A constant rapid flashing check engine light indicates that you have a fault in the ECM and it is operating in back up or limp home mode Make sure that the calibration chip is in the ECM and there are no bent pins on the chip If the chip is properly installed and there are no bent pins the ECM or the chip is faulty and needs to be replaced or repaired 14 My check engine light is on when the engine is running A check engine light indicates a hard fault with your fuel injection system Insure that all of your sensors are connected you have a good ground and that no wires are pinched Also insure no vacuum leaks and that your MAP sensor is connected to a full manifold vacuum source If all of these steps indicate a proper installation and no issues you will need to read the codes from the
33. tep Troubleshooting guide Your fuel injection system has been pre calibrated to your particular vehicle As long as the information about your engine was correctly stated the system as received will provide many years of trouble free use However from time to time problems are encountered with your fuel injection system Here are a few commonly asked questions about fuel injection problems Match the issue with the chart below for an explanation of the issue and use the troubleshooting fault tree Use of this section may require a digital voltmeter test light fuel pressure gauge timing light tachometer and or a diagnostic scan tool If you are familiar with vehicles and how they are serviced you should be able to work through this section with no issues In many instances you may want to have a professional automotive technician familiar with fuel injection repair to help you 1 My engine cranks but will not start 2 My engine is running to lean or is backfiring on acceleration 3 My engine is running rich 4 do not seem to have as much power as I should 5 I am getting a sag when I accelerate 6 My engine takes longer to start than I think it should 7 The fuel pump is not coming on when first turn the key on 8 The RPM on my engine does not come down when I come to an idle 9 I am not getting as good of fuel economy as I think should 10 The engine is revving up and down when come down to an idle There is a lar
34. voltage low vacuum at MAP sensor sensor could be unplugged Code 33 MAP High Verify Sensor is not unplugged If vehicle is equipped with a governor insure proper operation of the governor before using this chart If engine idle is rough unstable or incorrect correct any issues before using this chart Sensor is not unplugged Clear code and verify that the code still sets before moving on with diagnostics if any actions were taken Engine off Clear codes Start engine and run until check engine light comes on Gound diagnostic connector and note code Code 33 Clear codes Disconnect sensor and run engine for 1 minute or until CE light comes on Note the code that is set No Code set problem is intermittent Code 33 Check for short to voltage on Brown wire Pin B Key on engine off Backprobe with voltmeter between Pin B and Pin A With no vacuum applied voltage should be over 4 volts Apply 25 of vacuum with a hand held or similar vacuum pump Voltage should be approx 1 1 5 volts If these voltages are correct system is working as it should Look for loose or chaffed wires terminals or connectors See first note on idle conditions Code 34 If circuit is OK Replace ECM Check for Plugged or leaking Sensor vacuum hose If vacuum h
35. y or the frame real well Isolation brackets were provided with your fuel pump If these are properly installed it should isolate any radiated noise from the pump If this is insufficient you may need to isolate it more with some rubber grommets We have also diagnosed noisy fuel pumps with fuel return lines being too small By stepping up the size of the return line you may eliminate fuel pump noise after the other items have been addressed Fuel pump noise also can radiate through the fuel lines to the frame or body of the vehicle Insure that the fuel lines are isolated as well if need be to eliminate the noise A noisy fuel pump can also be an indication that it is starving for fuel Insure that all filters are in good order and that the fuel tank sock is clean Prolonged fuel starvation will damage the fuel pump and not allow proper flow it may also radiate a lot of noise 12 My check engine light does not come on when I turn the key on Your check engine light should illuminate when you turn the key to the on position for a bulb check Check for proper installation of check engine light a Check fuses to insure that they are not blown If fuses are OK go to b b Check voltage at check engine light if 12 volt are not present the check engine light is not connected properly If 12 volts are present either the ECM is not powered properly or is defective c If the fuse is OK insure that you are receiving 12 volts to the ECM where indica
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