Module 33 Evaporative Monitor
Contents
1. use the bi directional commands from a Mastertech scan tool using the Honda Software Version SNO10 or later If you do not have the capability to activate these valves with a scan tool you can always activate each one individually by providing a ground to the valve All the valves are fed battery voltage and the ECM provides the ground You can manually activate each valve by providing a ground at each of the valves You will need to first identify the power and ground wire on the sensor using a test light or DVOM Sure Seal Products Greensboro NC All Rights Reserved Page 33 10 Visit Our Website www tech2tech net Following is the menu sequence to follow to activate the solenoids with a Mas tertech scan tool using Honda software Version SNO1O or later TEST MODE MENU PGM FI DTCs DATA LIST FREEZE DATA SNAPSHOT CLEAR 6 INSPECT TOW T SETUP CPT Pe Ga DN pe INSPECTION MENU PGM FI 1 IDLE ADJUST 2 EVAP TEST 3 VTEC LOV T CHECK EVAP TEST MENU PGH F I 1 SINGLE SOLENOID 2 MULTI SOLENOIDS SINGLE SOLENOID MENU ES TEET 2 PCS OFF CUS ON CUS OFF BPS ON BPS OFF Screen Capture 33 2 This is the main menu of a Mastertech scan tool us ing the Honda software Version SNO10 or later From this menu choose 6 INSPECTION Screen Capture 33 3 From the Inspection Menu choose 2 EVAP TEST Screen Capture 33 4 From the Evap Test Menu choose 1 SINGLE SOLENOID To activat2. voltage rises to 1 5v start timing a 20 sec ond period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passed the leak check there is no problem If it failed the leak check go to step 7 Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 13 Leave the vacuum pump attached but pinch off the hose between the two way valve and the gas tank Note that on most models the two way valve is under the car and close to the gas tank such as shown in Im On a few models this valve is located under the hood Re run the leak check de scribed in Step 5 If the system passes the test there is a leak in the tank area If the system fails the test there is a leak in the two Sure Seal Products Greensboro NC All Rights Reserved Page 33 14 Visit Our Website www tech2tech net 33 4 P1456 Test Procedure For Under Car Canister Models Use this diagnostic procedure if you have a stored P1456 DTC This is an indica tion that you have a leak in the tank area of the system This procedure is for models with the canister mounted under the car For models with the canister mounted under the hood see Section 33 3 1 The gas tank should be at least 1 2 full but not com pletely full Pace OOOO is in place and tight 3 Apply vacuum until the FTP sensor reads 1 49v As soon as the voltage rises to 1 5v sta
3. way valve at the canister this 1s often labeled at the canister as Tank Attach a vacuum pump to this hose T Sctomsep ane test from step 8 18 If the system passes this leak check the canister is leaking replace the canis ter and retest the system If the system fails the test there is a leak in the two way valve bypass valve area Diagnose repair and retest the system Sure Seal Products Greensboro NC All Rights Reserved
4. Module 33 Evaporat ve Monitor Author Grant Swaim E mail sureseal nr infi net URL www tech2tech net Phone 336 632 9882 Fax 336 632 9688 Postal Address Tech 2 Tech Website PO Box 18443 Greensboro NC 27419 Physical Address 220 4 Swing Rd Greensboro NC 27409 Last Update October 2000 IMPORTANT READ Do not read or study this information unless you agree to the following conditions The information in this training module is the intellectual property of Grant Swaim and is copyrighted by Sure Seal Products Inc As a subscriber to the Tech 2 Tech website or the on line training Tech 2 Tech offers the following training modules in printed manual CD ROM and on line formats PGMFI Training Modules OBD II Training Modules The PGMFI System Overview Part 1 The PGMFI System Overview Part 2 PGMFI Flash Type DTCs Inputs Outputs Part 1 Inputs Outputs Part 2 Engine Control Module Air Flow MAP Sensor Base Inj Pulse Width Fuel Delivery System Closed Loop Strategies Theory Closed Loop Strategies Case Studies Thermistor Inputs Throttle Position Sensor EGR Valve Lift Sensor MAP BARO Sensor Ignition Inputs Vehicle Speed Sensor Oxygen Sensor Lean Air Fuel Sensor Miscellaneous Input Signals Fuel Injectors Multi Port Injection Fuel Injectors Dual Point Injection Ignition System Outputs Idle Air Control Valve e On Board Diagnostics General Overview e Diagnostic
5. Trouble Codes e MIL Freeze Frame e Scan Tool e Scan Tool Advanced e Monitor Tests Overview e Comprehensive Component Monitor e Catalyst Monitor e EGR Monitor e Evaporative Monitor e Fuel System Monitor e Misfire Monitor e Oxygen Sensor Monitor e Oxygen Sensor Heater Monitor e P Codes Miscellaneous Training Material e Glossary of Terms 2000 All Rights Reserved Sure Seal Products Inc Greensboro NC Visit Our Website www tech2tech net Page 33 1 33 Evaporative Monitor Enable Criteria Using an OBD II compatible scan tool monitor the ECT and IAT parameters The car must be started with an ECT and IAT sensor read ing of at least 32 F but not over 95 F The ECT and IAT sensors must be within 5 F of each other Fuel tank must not be over 85 full or below 15 full Monitor the bypass valve for activation to be assured the EVAP monitor has begun to run by either a Watching for the sensor s ground activation b Watching for the sensor s ON status with a Mastertech scan tool equipped with the Honda software Start the car If the bypass is activated at start up go to step 10 If the bypass valve is not activated within 3 seconds cut the car off Restart the car If the bypass valve is not activated within 3 seconds cut the car off The monitor is not going to run under the cur rent conditions Test drive the car as close to a steady road speed as possi ble Th
6. closed or off vent open The valve is normally open and is only closed by the ECM to run the EVAP leak check The valve is fed battery voltage directly and the ECM controls the ground You may manually activate this valve make it close by providing a ground to the valve at the valve or the ECM while the key is On 33 1 3 Two Way Valve By Pass Valve As you leave the canister headed towards the gas tank the next component you find is the two way valve by pass valve All Honda evaporative systems have a two way valve but only the enhanced systems have the by pass valve Image 33 3 Two Way and By Pass Valve The two way valve is usually located under the car and close to the gas tank A few models have the two way valve located under the hood The left ward pointing arrow in Image 33 3 shows the valve s location on a 2000 CR V The two way valve is a mechanical pressure controlling valve When the gas cap is installed all the tank venting both positive and negative is controlled by the two way valve When the tank pressure builds up to approximately 6 inHg either positive or negative the two way valve opens and allows the pressure to either vent the fumes to the canister or draw air into the tank The by pass valve is an electrically actuated solenoid type valve that is normally closed The valve is attached to the two way valve and is designed to allow the two way valve to be by passed when it is actuated Th
7. d systems Loose or improper gas REMOVE SLOW caps are the number one cause of EV AP monitor failures 33 2 Preliminary Testing Honda s enhanced evaporative system is tested for both proper canister purge and for leaks The EVAP monitor can also narrow a leak down to the tank part of the system or the canister part of the system When a tank area leak is detected on two consecutive EVAP monitor tests a P1456 DTC is stored When a canister area leak is detected on two consecutive EVAP monitor tests a P1457 DTC is stored The test procedures covered in this manual will concentrate on these two failures Section 33 2 will concentrate on preliminary tests that should be performed before any specific leak checks are performed Sections 33 3 amp 33 4 will concentrate on the tank area leaks which store a P1456 DTC Section 33 5 amp 33 6 will concen trate on the canister area leaks which store a P1457 DTC Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 7 33 2 1 Visual Inspection When checking a Honda that has stored a DTC indicating an evaporative system leak begin by performing a visual on the entire system Look for loose hose con nections unplugged electrical connectors or for any wreck damage to the evapo rative system components Keep in mind that evaporative components start at the intake manifold and end up at the gas tank Some systems have the canister under th
8. e EVAP monitor should run within approximately 5 miles You can find more information about the location and operation of the bypass valve in Section 33 1 3 Tn most cases the bypass valve will activate on and stay on for a long period In some cases the bypass valve is only activated for approximately 3 seconds Either one of these situations is an indi cation that the EVAP monitor is running DTC A diagnostic trouble codes DTC generated from this monitor is stored on the second malfunction first malfunction on a purge flow switch during a consecutive running of the monitor All DTCs set from this monitor are standard priority within the freeze frame writing strategy A freeze frame written by one of these DTCs can only be over written by a high priority DTC not another standard priority DTC MIL Info illumination Sure Seal Products Greensboro NC All Rights Reserved Page 33 2 General Info Visit Our Website www tech2tech net The malfunction indicator light MIL is illuminated when a sec ond first on purge flow switch malfunction DTC is stored Extinguishing The MIL is extinguished after three trips without a malfunction reoccurring Hondas are equipped with an evaporative system that stores fuel vapors during parked periods and burns those vapors during run ning periods Some of the newer models also have an on board refueling vapor recovery ORVR system to capture fuel vapors during ref
9. e by pass valve is indicated by the down ward pointing arrow in Image 33 3 The two way valve is only by passed during the EVAP monitor leak checks The valve is fed battery voltage directly and the ECM controls the ground You may manually activate this valve make it open and bypass the two way valve by providing a ground to the valve at the valve or the ECM while the key is On Sure Seal Products Greensboro NC All Rights Reserved Page 33 6 Visit Our Website www tech2tech net 33 1 4 Fuel Tank Pressure FTP Sensor All enhanced systems are also equipped with a fuel tank pressure FTP sensor The sensor 1s a 5v reference type sensor that produces a voltage that is propor tional to the gas tank s pressure The FTP sensor is connected to the two way valve by a short hose The FTP sensor is indicated by an up ward pointing arrow in Image 33 3 When the tank is not pressured is open to the atmosphere the FTP reading should be between 2 45 2 55v You may read this with a digital volt ohm meter DVOM or with a Mastertech scan tool equipped with Honda software 33 1 5 Enhanced System Gas Cap Image 33 4 Enhanced System Cap The gas cap is also different on an enhanced system The gas cap on an enhanced system should contains the words Tf not tightened 3 clicks check engine light may come on E be a ay Beall tees st ENa Image 33 4 shows the proper gas cap for the HONDA MOTOR C0 u enhance
10. e hood and some have the canister under the car The two way and bypass valves are usually located under the car also You will need to put the car on a lift to do a thorough visual inspec tion of the evaporative system If diagnosing an evaporative leak after any significant body damage be sure to check all the components for cracks Most of the components are plastic and can be easily damaged Also the steel lines located underneath the car that run from the front of the car to the rear of the car should be closely inspected after any body damage 33 2 2 Gas Cap One of the biggest causes of evaporative leak check failures is an incorrect gas cap or loose gas cap Confirm that the gas cap is in fact the correct one for an en hanced evaporative system Refer to Section 33 1 5 for more information about the enhanced system gas cap If the gas cap is the correct part you will need to confirm that it is tight Before you twist on the gas cap you might want to do a quick preliminary check to see if the cap was loose when it came in You can do this by determining if the tank is leaking before you check the tightness of the cap then see if the leak stops after you tighten and or replace the cap Screen Capture 33 1 To do a quick check for a leaking gas cap start by checking the fuel tank pressure FTP sensor volt age This can be done with a DVOM or a Mas tertech scan tool equipped with Honda software Screen Capture 33 1 is from a Mast
11. e the valves one at a time 2 MULTI SOLENOIDS To activate more than one valve at a time Screen Capture 33 5 From the Single Solenoid Menu you can activate and deactivate each of the three evaporative valves Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 11 MULTI SOLENOIDS MENU PCS ON CVS ON nd BPS ON a PCS OFF CVS ON and BPS OFF 3 PCS OFF CVS OFF and BPS ON Screen Capture 33 6 From the Multi Solenoids Menu you can activate more than one of the evaporative valves in different combinations Sure Seal Products Greensboro NC All Rights Reserved Page 33 12 Visit Our Website www tech2tech net 33 3 P1456 Test Procedure For Under Hood Canister Models Use this diagnostic procedure if you have a stored P1456 DTC This is an indica tion that you have a leak in the tank area of the system This procedure is for models with the canister mounted under the hood For models with the canister mounted under the car see Section 33 4 The gas tank should be at least 2 full but not com pletely full 2 Make sure the proper cap is in place and tight Activate the Bypass Valve See Section 33 2 4 4 Disconnect the hose be tween the two way valve and canister at the canister This hose is usually la beled Tank on the canis ter Connect a vacuum pump to the hose 5 Apply vacuum until the FTP sensor reads 1 49v As soon as the
12. em If the system failed this leak test go to step 7 Disconnect the hose from the purge control valve to the canister from the purge control valve Attach a vacuum pump to this hose Apply vacuum until the FTP sensor reads 1 49v As soon as the voltage rises to 1 5v start timing a 20 sec ond period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passes this leak check the purge con trol valve is leaking re place the valve and retest If the system fails the test go to step 10 Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Ee eee 33 19 With the vacuum pump Image 33 14 a still attached pinch off the w 4 4 canister vent shut valve z Poe ae hose k ee r 2 Di z i T a gan a 3 d z A n Re test for a leak using the test from step 8 12 If the system passes this leak check the canister vent shut valve is leaking replace the valve and re test If the system fails the test go to step 13 Disconnect the hose from the canister and two way valve at the canister this 1s often labeled at the canister as Tank Attach a vacuum pump to this hose Sure Seal Products Greensboro NC All Rights Reserved NN y Pireti Page 33 20 Visit Our Website www tech2tech net la test from step 8 If the system passes this leak check the canister 1s leaking
13. ems by 1998 This training module concentrates on the enhanced systems The enhanced systems are composed of these main components Valve tain proper canister purge Canister Vent The valve is normally open and is only commanded shut Shut CVS by the ECM when it is leak checking the evaporative sys Valve tem The canister stores the gas tank emissions during parked periods The canister is purged during driving periods Two Way Valve This mechanical valve allows the gas tank to vent when the pressure exceeds approx 6 inHg either positive or negative E Bypass Valve During a leak check the ECM activates the bypass valve which bypasses the two way valve F Fuel Tank Pres A 5v reference type sensor that produces a voltage propor sure FTP Sen tional to tank pressure A tank with no pressure produces a sor FTP sensor voltage of 2 45 2 55v Gas Tank With The gas tank filler cap for an enhanced evaporative system Special Filler is specially designed Cap Sure Seal Products Greensboro NC All Rights Reserved Page 33 4 Visit Our Website www tech2tech net 33 1 1 Purge Control Valve Image 33 1 Purge Control Valve on a 2000 CRV The purge control valve is a duty cycled solenoid type valve The valve is normally closed The valve is fed battery voltage di rectly and the ECM controls the ground You may manually acti vate this valve by providing a ground to the valve at the valve or the ECM while the ke
14. ertech For more information about reading the FTP sensor voltage ets see Section 33 2 3 IAC COMMAND EVAP PC DUTY When there is no pressure on the tank the FTP sen sor voltage should read between 2 45 2 55v As tank pressure rises the voltage will rise above this level As the tank pressure decreases the voltage will drop below this level Sure Seal Products Greensboro NC All Rights Reserved Page 33 8 Visit Our Website www tech2tech net With the ever changing temperature of the fuel in the gas tank it is rare that the FTP sensor reads 2 5v For instance 1f a car has sat outside and has cooled over night it is normal for the FTP sensor voltage to be under 2 5v If a car is sitting outside during the day where the temperature has risen significantly it is normal to see a FTP sensor reading over 2 5v Due to the fuel being constantly pumped to the fuel rail and returned to the tank except for return less systems on some 2001 models the fuel in the tank will usually rise at least 30 F ona running Honda This means that a running Honda will almost always have a rising FTP sensor voltage If the ambient temperature is extremely cold or falling this may not be the case With this in mind before disturbing the gas cap check the FTP sensor voltage If the reading is 2 5v yet conditions exist that would normally created a high or low tank pressure then there probably is a leak Then tighten the cap to see if the ta
15. l Rights Reserved Visit Our Website www tech2tech net Page 33 9 one should have a ground less than 50mv on it and one will have the input volt age of approx 2 5v Fuel Tank Pressure Sensor Test 1 Remove the gas cap 2 Make sure the tank is not completely full drain out gas as needed 3 With key on engine off KOQEO Check the FTP sensor voltage It should be between 2 45 2 55v and steady If so the sensor is good If not go to step 4 4 Disconnect the hose between the FTP sensor and the two way valve 5 With KOEO recheck the FTP sensor voltage It should be between 2 45 2 55v and steady If so the sensor is good however there is a restriction in the evaporative system go to step 5 If not replace the FTP sensor and re test 6 Look for a restriction between the FTP and the gas tank This is usually caused by a defective onboard refueling vapor recycling ORVR system which allows gasoline to enter the evaporative system If gas 1s present replace all components exposed to the gas replace the ORVR valve and re test the FTP sensor 33 2 4 Solenoid Check The last step in the preliminary checks is to confirm that each of the three electri cally activated valves purge control canister vent shut and bypass do respond to activation You should activate each valve and confirm that the valve clicks whole holding it Replace any defective valves and retest the system The easiest way to activate these valves is to
16. nk pressure changes over the next 15 20 minutes If it does the gas cap was not tight enough If tightening the cap did not make a difference try a known good gap and see if the tanks pressure changes If so the original cap is bad The best way to create a situation where the fuel tank pressure should be changing is to heat up the fuel in the tank by running the engine which will cause a pres sure rise A Honda running at least 20 minutes should have a rising FTP sensor voltage On a hot day the FTP sensor voltage will quickly reach the maximum of about 3 1v The two way valve will bleed off any pressure above this 33 2 3 Check FTP sensor Image 33 5 Since almost all evaporative leak checks revolve around the FTP sensor output you need to start by checking it first The FTP sensor has three wires and 1s a 5 volt reference type sensor The ECM supplies a reference volt age Sv and a ground to the sen sor over two of the wires The FTP sensor returns back an ana log voltage to the ECM over the third wire While this is a listed parameter on a Mastertech scan tool equipped with Honda soft ware you can also get this volt age using a standard DVOM Image 33 5 shows the FTP sensor on a 2000 CRV Note the 3 wire connector If checking the FPT sensor voltage using a DVOM simply back probe this connec tor until you find the input wire Remember one wire should have approx 5v on it Sure Seal Products Greensboro NC Al
17. replace the canis ter and retest the system If the system fails the test there is a leak in the two way valve bypass valve area Diagnose repair and retest the system Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 21 33 6 P1457 Test Procedure For Under Car Canister Models Isolate the fuel tank from the system by clamping off the hose that goes from the two way valve to the fuel tank Activate the purge control 2 valve canister vent shut valve and bypass valve either manually or by using the Mastertech scan tool See Section 33 2 4 Disconnect the hose be tween the intake manifold and the purge control valve at the manifold Attach a vacuum pump to this hose Apply vacuum until the FTP sensor reads 1 49v Then disconnect the purge control valve and vent the vacuum pump Sure Seal Products Greensboro NC All Rights Reserved lc a 33 22 Visit Our Website www tech2tech net As soon as the voltage rises to 1 5v start timing a 20 second period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passes this leak check there is no problem If the system failed this leak test go to step 7 Disconnect the hose from the purge control valve to the canister from the purge control valve Attach a vacuum pump to this hose Apply vacuum until the FTP sensor reads 1 49v As
18. rt timing a 20 sec ond period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passed the leak check there is no problem If it failed the leak check go to step 7 ea 4 Disconnect the hose be tween the two way valve and canister at the canister This hose is usually la beled Tank on the canis ter Connect a vacuum pump to the hose Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 15 7 Ifthe car is equipped with Image 33 9 an ORVR system follow this step if not skip to step 10 If the car 1s equipped with the ORVR system it will have an third hose attached to the canister The hose is large in size and is attached to the canister with a quick disconnect type fitting Disconnect the ORVR hose from the canister and plug the hose Re run the leak check de scribed in Step 5 If the system passes the test replace the ORVR If the system fails the test reconnect the ORVR hose and proceed to step 10 10 Leave the vacuum pump ee B attached but pinch off the AA e A SOA hose between the two way 7 3 N DOI GON valve and the gas tank ae E Was i BA 4 A Er Cj a L i q p J r I i w k 11 Re run the leak check de B scribed in Step 5 Sure Seal Products Greensboro NC All Rights Reserved Page 33 16 Visit Our Website www tech2tech net If the system pas
19. ses the test there is a leak in the tank area If the system fails the test there is a leak in the two way bypass valve area 13 Diagnose leak repair and retest the system Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 17 33 5 P1457 Test Procedure For Under Hood Canister Models Isolate the fuel tank from Image 33 11 __ the system by clamping off fm i wa the hose that goes from the i 1 Se two way valve to the fuel tank Note that on most models the two way valve is under the car and close to the gas tank such as shown in Im age 33 11 On a few models this valve is located under the hood Activate the purge control valve canister vent shut valve and bypass valve either manually or by using the Mastertech scan tool See Section 33 2 4 Disconnect the hose be tween the intake manifold and the purge control valve at the manifold Attach a vacuum pump to this hose Image 33 12 Apply vacuum until the FTP sensor reads 1 49v Then disconnect the purge control valve and vent the 4 vacuum pump Sure Seal Products Greensboro NC All Rights Reserved eee eee 33 18 Visit Our Website www tech2tech net As soon as the voltage rises to 1 5v start timing a 20 second period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passes this leak check there is no probl
20. soon as the voltage rises to 1 5v start timing a 20 sec ond period If the voltage rises above 1 55v in 20 seconds the leak check has failed If the system passes this leak check the purge con trol valve is leaking re place the valve and retest If the system fails the test go to step 10 Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net ee ee eee 33 23 10 With the vacuum pump still attached pinch off the canister vent shut valve hose ns 33 19 tt Re test for a leak using the tt Re from step 8 12 If the system passes this leak check the canister vent shut valve is leaking replace the valve and re test If the system fails the test 13 go to step 13 If the Honda is equipped with the ORVR system follow this step if not jump to step 16 If the car is equipped with the ORVR system the can ister will have a third hose The hose is large and is attached to the canister by a quick disconnect type fitting Disconnect the ORVR vent hose and plug the canister 14 Re test for a leak using the test from step 8 Sure Seal Products Greensboro NC All Rights Reserved eee ee ee 33 24 Visit Our Website www tech2tech net If the system passes this leak check the ORVR valve is leaking replace the valve and retest If the system fails the test go to step 16 16 Disconnect the hose from maze 33 21 the canister and two
21. ueling The evaporative systems fall into two different types standard and enhanced Both systems are checked for proper purge flow through the EVAP canister Only the enhanced systems are checked for leaks by the EVAP monitor Only a few 1996 models were equipped with the enhanced sys tems By 1998 all models were equipped with the enhanced sys tem As on most OBD II equipped vehicles the Honda evaporative system 1s somewhat complex For example in the 1998 Accord service manual the evaporative diagnostic and repair procedures include over 85 steps and 30 illustrations The remainder of this chapter is devoted to a diagnostic proce dure for testing the evaporative system for leaks This procedure is very effective and much easier to follow than most procedures covered in service manuals DTCs Generated by the EVAP Monitor MIL Trips Description Flash VAP Insufficient Purge Flow 90 2 V AP Leak Detected Fuel Tank System 90 2 2 EVAP Leak Detected Control Canister System VAP Purge Flow Switch Malfunction Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 3 33 1 Evaporative System General Overview Honda uses two different evaporative systems the standard system that checks for canister purge flow only and the enhanced systems that add leak detection En hanced systems are found on a few 1996 models and were added to all syst
22. y is On The ECM controls the amount of air that purges the evaporative canister by duty cycling this valve which applies manifold vacuum to the evaporative sys tem The duty cycle of the purge control valve varies widely based on many en gine conditions The canister is typically not purged at idle and is purged more at higher speeds The valve s duty cycle can be measured directly with a digital storage oscillo scope DSO or with a Mastertech scan tool equipped with Honda software The purge control valve is usually mounted on the intake manifold the left shock tower or the firewall One way to identify the purge control valve is to follow the hose from the canister back towards the engine 33 1 2 Canister Canister Vent Shut CVS Valve Image 33 2 Canister on a 2000 Accord As you follow the hose from the purge control valve towards the tank the next component you will find is the canister The can ister is either located under the car usually in front of the gas tank or under the hood on the firewall Image 33 2 is the can ister on a 2000 Accord and it is located under the car If the evaporative system is an enhanced version the canister will have a canister vent shut Sure Seal Products Greensboro NC All Rights Reserved Visit Our Website www tech2tech net Page 33 5 CVS valve mounted on it The CVS valve is an electrically activated solenoid type valve that is either on valve
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