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Diagnostic Aids

WARNING: This page is about a different car, the 1996 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

Perform this test when instructed during QUICK TEST  or if directed by other test procedures. This test is used to diagnose the following:

Fig 1: EVAP Components Using Purge Flow System
G95I12607
Fig 2: EVAP Components Using Vapor Management System
G95D27220
Fig 3: VMV Test Circuit & Connector Terminals
G95J35997
  1. Step 1) DTC P0443: Check VPWR Circuit Voltage  Disconnect canister purge valve or Vapor Management Valve (VMV) wiring harness connector. Turn ignition on. Measure voltage between VPWR terminal of canister purge valve or VMV wiring harness connector and battery ground. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open in VPWR circuit and repeat QUICK TEST .
  2. Step 2) Check Component Resistance  Turn ignition off. Leave canister purge valve or VMV wiring harness connector disconnected. Measure resistance between canister purge valve or VMV terminals. For canister purge valve, if resistance is 30-90 ohms, go to next step. For VMV, if resistance is 30-36 ohms, go to step 4). If resistance is not as specified, replace canister purge valve or VMV. Clear PCM memory and repeat QUICK TEST .
  3. Step 3) Check CANP Solenoid For Internal Short  Turn ignition off. Leave wiring harness connector disconnected. Measure resistance between each solenoid terminal and canister purge valve housing. If each resistance measurement is more than 90 ohms, canister purge valve is okay. Go to next step. If resistance is not as specified, replace canister purge valve. Clear PCM memory, repeat QUICK TEST .
  4. Step 4) Check VMV Circuit Continuity  Leave ignition off and canister purge valve or VMV wiring harness connector disconnected. Disconnect PCM wiring harness connector. Inspect pins for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance as follows:
    • For canister purge valve, between test pin No. 67 at breakout box and EVAP canister purge terminal of canister purge valve wiring harness connector.
    • For VMV, between test pin No. 56 at breakout box and VMV terminal of VMV wiring harness connector.

    If resistance is less than 5 ohms, go to next step. If resistance 5 ohms or more, repair open circuit and repeat QUICK TEST .

  5. Step 5) Check Circuit For Short To PWR GND  Leave ignition off. Disconnect scan tester from DLC (if applicable). Measure resistance between test pin No. 67 (canister purge valve) or 56 (VMV) and test pins No. 24 and 103. If each resistance is more than 10,000 ohms, go to step 22). If resistance is 10,000 ohms or less, repair EVAP canister purge/VMV circuit short to PWR GND circuit. Clear PCM memory and repeat QUICK TEST .
  6. Step 6) Continuous Memory DTC P1443  This DTC can set by Idle Air Control (IAC) valve speed error during vehicle operation. If Continuous Memory DTC P1507 is also present, go to CIRCUIT TEST KE, step 30). Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access IAC PID, TP PID and RPM PID. Turn all accessories off. Start engine and allow to idle. IAC duty cycle should be 20-45%. Observe IAC PID and RPM PID for indication of fault while shaking and bending IAC valve wiring harness and connector. A fault will be indicated by sudden increase of engine speed and decrease in IAC duty cycle. If fault indicated, isolate/repair as necessary. If no fault go to step 8).
  7. Step 7) Check Purge Flow (PF) Sensor  Connect scan tester to Data Link Connector (DLC). Start engine and allow to idle. Disconnect PF sensor wiring harness connector. Inspect connector for damage and repair if necessary. Using scan tester, access PF PID. If voltage fluctuates about 0.9-1.1 volts, go to step 19). If voltage fluctuates 2.2-2.6 volts, go to step 18). If voltage does not fluctuate as specified, go to next step.
  8. Step 8) Visual Check Of EVAP System  Check for kinked or pinched fuel vapor tubes/hoses between EVAP canister, EVAP canister purge valve and engine intake manifold. Check for cracked or smashed EVAP canister. If a fault is indicated, repair fuel vapor tubes/hoses as necessary. If EVAP canister is cracked or smashed, replace EVAP canister. If components are replaced, go to step 42). If fault is not indicated, go to next step.
  9. Step 9) Check VPWR Voltage To EVAP Canister Purge Valve  Disconnect EVAP canister purge valve harness connector. Turn ignition on, engine off. Measure VPWR circuit voltage between EVAP canister purge valve harness connector and battery negative post. Turn ignition off. If the voltage was greater than 10.5 volts, go to next step. If the voltage was not greater than 10.5 volts, repair open circuit. Clear DTCs and repeat QUICK TEST .
  10. Step 10) Check For Intake Manifold Vacuum To Canister  Install breakout box, connect PCM to breakout box. Disconnect fuel vapor hose to EVAP canister purge valve at EVAP canister. Install a vacuum gauge to open end of fuel vapor hose. Start engine. Idle engine for 5 minutes. Observe the vacuum gauge. Reading must be near 0 in. Hg (0 kPa). Connect a jumper between PCM test pins No. 51 and 56 or 103, while engine is still running. Idle the engine for additional 5-10 minutes. Observe the vacuum gauge. Turn ignition off. If the vacuum reading changes from near 0 in. Hg (0 kPa) to 10 in. Hg (33.77 kPa) or greater with addition of jumper, remove vacuum gauge. Inspect the fuel vapor tubes/hoses between the EVAP canister and the EVAP canister purge valve and between the EVAP canister purge valve and the intake manifold for small cracks, splits or holes. Repair as necessary and go to next step. If the vacuum reading does not change from near 0 in. Hg (0 kPa) to 10 in. Hg (33.77 kPa) or greater with addition of jumper, remove vacuum gauge. Leave the fuel vapor hose from EVAP canister disconnected. For vacuum readings within 6-10 in. Hg (20.26-33.77 kPa), go to step 12). For vacuum readings less than 6 in. Hg (20.26 kPa), go to step 13).
  11. Step 11) Check EVAP Canister  Disconnect fuel vapor hose to EVAP canister purge valve at EVAP canister. Check for contamination or blockages at all ports on EVAP canister (to the fuel tank, to the EVAP canister purge valve and to the atmosphere). If a fault is indicated, repair EVAP canister. If components are replaced, go to step 42). If a fault is not indicated, go to next step.
  12. Step 12) Check For Leak Between EVAP Canister Purge Valve And EVAP Canister  Disconnect other end of fuel vapor hose from EVAP canister at EVAP canister purge valve. Plug open end of fuel vapor hose at EVAP canister. Install a hand vacuum pump to open end of fuel vapor hose at EVAP canister purge valve. Apply 16 in. Hg (53 kPa) of vacuum with vacuum pump. If the vacuum pump holds the vacuum, remove plug in hose. Go to next step. If the vacuum pump does not hold the vacuum, replace damaged fuel vapor hose. After repair, go to step 42).
  13. Step 13) Check For Blockage Between EVAP Canister Purge Valve And EVAP Canister  Disconnect other end of fuel vapor hose from EVAP canister at EVAP canister purge valve. Install a hand vacuum pump to open end of fuel vapor hose at EVAP canister purge valve. Apply 16 in. Hg (53 kPa) of vacuum with vacuum pump. If the vacuum pump holds the vacuum, remove vacuum pump. Repair or straighten fuel vapor hose as necessary and go to step 42). If the vacuum pump does not hold the vacuum, remove vacuum pump. Reconnect fuel vapor hose between EVAP canister and EVAP canister purge valve and go to next step.
  14. Step 14) Check For Filter Contamination Or Damage To EVAP Canister Purge Valve  Disconnect vacuum line from input vacuum port to intake manifold on EVAP canister purge valve. Install a hand vacuum pump to input vacuum port on EVAP canister purge valve. Apply 10-15 in. Hg (48-52 kPa) of vacuum to EVAP canister purge valve. If the EVAP canister purge valve holds vacuum or shows a very slow release of vacuum to atmosphere, repair EVAP canister purge valve filter blockage or replace EVAP canister purge valve. After repair, go to step 42). If the EVAP canister purge valve does not hold vacuum and releases of vacuum to atmosphere, remove vacuum pump and go to next step.
  15. Step 15) Check For Vacuum At VMV  Ensure EVAP canister purge valve is electrically connected. Disconnect both input port vacuum and fuel vapor hoses from intake manifold vacuum source and fuel vapor ports at EVAP canister purge valve. Install a vacuum gauge (two gauges or one gauge at a time) to open end of input port vacuum hose and open end of the fuel vapor hose at EVAP canister purge valve. Start engine. If both vacuum gauge readings are greater than 10 in. Hg (33.77 kPa), leave input port vacuum and fuel vapor hoses to the intake manifold at EVAP canister purge valve disconnected and go to next step. If either vacuum reading is not greater than 10 in. Hg (33.77 kPa), isolate causes of missing intake manifold vacuum. Repair partially unconnected hoses or kinked/blocked hoses to intake manifold. Remove vacuum gauge(s), clear DTCs and go to step 42).
  16. Step 16) Check For Restrictions Between EVAP Canister Purge Valve And Intake Manifold  Disconnect input port vacuum hose and fuel vapor hose from EVAP canister purge valve at intake manifold (other end of hoses are already disconnected). Install a hand vacuum pump to one end of each completely disconnected hose from EVAP canister purge valve to intake manifold. Apply 16 in. Hg (53 kPa) of vacuum with vacuum pump. Observe the vacuum reading for 30 seconds. If the vacuum bleeds off immediately, remove vacuum pump. Correct minor concerns with input vacuum hose and fuel vapor hose between EVAP canister purge valve and intake manifold. If hoses were okay, replace damaged EVAP canister purge valve and go to step 42). If vacuum does not bleed off immediately, remove vacuum pump. Remove blockages or minor kinks in input vacuum hose and fuel vapor hose between EVAP canister purge valve and intake manifold. Drive vehicle and go to step 42).
  17. Step 17) Check VPWR To EVAP Canister Purge Valve  Disconnect EVAP canister purge valve harness connector. Turn ignition on, engine off. Measure VPWR circuit voltage between EVAP canister purge valve harness connector and battery negative post. Turn ignition off. If the voltage was greater than 10.5 volts, go to next step. If the voltage was not greater than 10.5 volts, repair open circuit. Clear DTCs and repeat QUICK TEST .
  18. Step 18) Check Canister Purge Valve Stuck Open Or PF Sensor Damage  Disconnect fuel vapor hose from intake manifold at PF sensor. Reconnect the EVAP canister purge valve (electrically). Install a hand-held vacuum pump to intake manifold side of PF sensor. Apply 16 in. Hg (53 kPa) of vacuum to open end of PF sensor. If the EVAP canister purge valve-PF sensor assembly holds vacuum for 20 seconds, leave the vacuum pump connected and go to next step. If the EVAP canister purge valve-PF sensor assembly does not hold vacuum for 20 seconds, replace PF sensor if PF sensor housing is cracked. Otherwise, replace fuel vapor hose between EVAP canister purge valve and PF sensor. If fuel vapor hose was okay, replace EVAP canister purge valve. After repair, go to step 42).
  19. Step 19) Check Hose Blockage Or EVAP Canister Purge Valve Stuck Open  Connect scan tool. Apply 16 in. Hg (53 kPa) of vacuum to open end of PF sensor. Turn ignition on, engine off. Access OUTPUT TEST MODE on the scan tool to cycle EVAP canister purge valve. Turn ignition off. If the EVAP canister purge valve opens and vacuum reading on the vacuum pump drops (air passes freely) when commanding the output on, remove vacuum pump and go to next step. If the EVAP canister purge valve opens and vacuum reading on the vacuum pump does not drop (air passes freely) when commanding the output on, remove the vacuum pump. Remove blockages in fuel vapor hose between EVAP canister purge valve and PF sensor. If okay, replace EVAP canister purge valve and go to step 42).
  20. Step 20) Check Vacuum To PF Sensor  Install a vacuum gauge to the open end of fuel vapor hose (intake manifold side) at PF sensor. Start engine. Observe vacuum gauge at idle. Turn ignition off. If the vacuum gauge reading was greater than 10 in. Hg (33.77 kPa) with engine running, check for small vacuum leaks between PF sensor and intake manifold. Repair as necessary. Drive vehicle and go to step 42). If the vacuum gauge reading was not greater than 10 in. Hg (33.77 kPa) with engine running, remove blockage, reconnect loose fuel vapor hose or replace cracked, split fuel vapor hose between the PF sensor and intake manifold. After repair, go to step 42). If DTC P1443 is still present, go to next step.
  21. Step 21) Check EVAP Canister Purge Valve Resistance  Disconnect EVAP canister purge valve. Measure EVAP canister purge valve resistance. If the resistance is 30-90 ohms, go to next step. If resistance is not 30-90 ohms, replace damaged EVAP canister purge valve. After repair, go to step 42).
  22. Step 22) Check EVAP Canister Purge Circuit For Short To VPWR  Install breakout box, leave PCM disconnected. Measure resistance between PCM test pin No. 67 or PCM test pin No. 56 and PCM test pin No. 71. If resistance is greater than 10,000 ohms, replace the PCM. Access the EVAPPDC PID on the scan tool. DRIVE vehicle (including a steady accelerator speed over 50 mph (80 km/h) until the EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Repeat QUICK TEST . If resistance is not greater than 10,000 ohms, repair short circuit and clear DTCs. Access the EVAPPDC PID on the scan tool. DRIVE vehicle (including a steady accelerator speed over 50 mph (80 km/h) until the EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Repeat QUICK TEST .
  23. Step 23) Check Leak Through EVAP Service Port  Remove atmospheric vent cap (blue or black) on EVAP canister(s) or canister vent line. Plug (or tape) open vent on EVAP canister(s). Disconnect and plug fuel vapor hose to PF sensor (or EVAP canister purge valve) from intake manifold at the intake manifold vacuum source. Locate evaporative emission test port (marked EVAPORATIVE SERVICE PORT) between EVAP canister purge valve and EVAP canister. If vehicle does not have a test port, go to next step. Access the Rotunda Evaporative Emission System Tester (134-00056), including the compressed gas source (nitrogen or argon) and pressure regulator. Perform a Tester Self-Test using the instructions provided with the Tester Kit. Regulate the gas pressure on the Tester to 27 in. H2O (6.74 kPa). Install the Rotunda Evaporative Emission System Tester to the test port and follow the system leak test instructions provided with the Tester Kit. If the pressure is not 26-28 in. H2O (6.46-6.97 kPa), use the ultra-sonic leak detector provided with the Tester Kit to check for leakage at the vehicle's fuel filler cap and filler pipe assembly. If a leak is indicated, remove and verify fuel filler cap according to original equipment specifications. Replace damaged fuel filler cap. Reinstall fuel filler cap and tighten cap only one eighth turn so that cap initially clicks by sound or touch. Repeat evaporative emission system leak test using Tester. If the leak is still present, repair or replace fuel tank, fuel filler pipe, fuel vapor valve or fuel vapor hose between fuel tank and EVAP canister as necessary. Verify a symptom no longer exists. If leak is not indicated, go to next step.
  24. Step 24) Check EVAP System Using EVAP System Tester  Remove the fuel filler cap. Install the Rotunda Evaporative Emission System Tester (134-00056), including the compressed gas (nitrogen or argon) and pressure regulator. Tester kit contains all required adapters (Schrader valve and fuel filler cap per vehicle application). Turn ignition on, engine off. Pressurize the vehicle evaporative emission system to 27 in. H2O (6.74 kPa) using the Evaporative Emission System Tester and the instructions that come with the tester. If a system leak is indicated by the tester Red light on, allow the two-position control on the tester to provide a continuing flow of the gas to the closed evaporative emission system. Maintain 27 in. H2O (6.74 kPa) pressure on the system (monitor tester pressure gauges) and go to next step. If a system leak is not indicated by the tester Red light on, remove Evaporative Emission System Leak Tester. Complete PCM Reset to clear DTCs. Access the EVAPPDC PID on the scan tool. Drive vehicle (including a steady accelerator speed over 50 mph (80 km/h) until the EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Repeat QUICK TEST  to verify a symptom no longer exists.
  25. Step 25) Check For Fuel Vapor Hose Restrictions  Turn ignition on, engine off. Disconnect and plug the fuel vapor hose from the EVAP canister(s) at EVAP canister purge valve. Reinitiate pressurizing of vehicle evaporative emission system using the Rotunda Evaporative Emission System Tester. When pressure on the evaporative emission system is stabilized close to 27 in. H2O (6.74 kPa), record the reading. Remove the plug at the fuel vapor hose to EVAP canister at the EVAP canister purge valve. Observe pressure gauges on tester. If the pressure immediately drops, remove plugs. REINSTALL the dust cap (blue or black) on EVAP canister or canister vent line at canister and go to step 42). If the pressure does not immediately drop, remove blockages and straighten fuel vapor tubes/hoses between fuel tank, EVAP canister purge valve and EVAP canister(s). Remove plugs. Reinstall the dust cap (blue or black) on EVAP canister and go to step 42).
  26. Step 27) DTC P1444: Check PF Sensor Low Voltage To PCM  Disconnect PF sensor. Check for loose pins or broken wires by pulling moderately on the VPWR circuit at PF sensor harness connector. Repair as necessary. Reconnect PF sensor. Connect scan tool. Turn ignition on, engine running. Access EVAPPF PID (PF sensor input range to the PCM is 0.40 to 4.80 volts). Turn ignition off. If EVAPPF PID voltage was less than 0.40 volt, for EVAPPF PID voltage between 0.20 and 0.40 volt, go to next step. For EVAPPF PID voltage less than 0.20 volt, go to step 30). If EVAPPF PID voltage was not less than 0.40 volt, fault is an intermittent DTC P1444, go to step 32).
  27. Step 28) Check For Open VPWR Circuit In PF Sensor  Disconnect PF sensor. Allow the vehicle and PF sensor to cool down or warm up to room temperature 55-80°F (13-27°C) before taking a resistance measurement on the PF sensor. This can take 15 to 20 minutes. Measure resistance between VPWR pin and PF, PWR GND pins on the PF sensor. See Fig 4. If resistance is greater than 160 ohms between VPWR and PF pins or greater than 190 ohms between VPWR and PWR GND pins, replace damaged PF sensor. Record data from this test step and go to step 42). If resistance is not greater than 160 ohms between VPWR and PF pins or not greater than 190 ohms between VPWR and PWR GND pins, go to next step.
    Fig 4: PFS Sensor Connector Terminals
    G95I27233
  28. Step 29) Check VPWR Circuit For Open  Install breakout box, leave PCM disconnected. Measure resistance of VPWR circuit between PCM test pin No. 71 and PF sensor harness connector. If resistance is less than 5.0 ohms, leave breakout box installed. For DTC P1444, go to next step. For DTC P1445, go to step 34). If resistance is not less than 5.0 ohms, repair open circuit. Clear DTCs, repeat QUICK TEST  to verify a symptom no longer exists.
  29. Step 30) Check For Short To PWR GND In PF Sensor  Disconnect PF sensor. Allow the vehicle and PF sensor to cool down or warm up to room temperature 55-80°F (13-27°C) before taking a resistance measurement on the PF sensor. This can take 15 to 20 minutes. Measure resistance between PWR GND and PF pins on the PF sensor. If resistance is less than 25.5 ohms, replace damaged PF sensor and go to step 42). If resistance is not less than 25.5 ohms, go to next step.
  30. Step 31) Check PF Sensor Circuit For Short To PWR GND  Install breakout box, leave PCM disconnected. Disconnect scan tool from DLC. Measure resistance between PCM test pin No. 11 and PCM test pins No. 24 and 103. If both resistances are greater than 10,000 ohms, replace damaged PCM. Reconnect all disconnected connectors and components. Repeat QUICK TEST . If either resistance is not greater than 10,000 ohms, repair short circuit. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST .
  31. Step 32) Check PF Sensor Circuit For Intermittent VPWR Open Or PWR GND Short  Turn ignition on, engine off. Access EVAPPF PID. Observe EVAPPF PID for an indication of a fault while lightly tapping on PF sensor and wiggling PF sensor connector and harness between sensor and PCM. A fault is indicated by a sudden change in EVAPPF PID voltage (less than 0.14 volt). If a fault is indicated, isolate fault and repair as necessary. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST . If a fault is not indicted, unable to duplicate or identify fault at this time. Go to test Z, step 1).
  32. Step 33) DTC P1445: Check PF Sensor High Voltage To PCM  Disconnect PF sensor. Check for loose pins or broken wires by pulling moderately on the PF and PWR GND circuits at PF sensor harness connector. Repair as necessary. Reconnect PF sensor. Connect scan tool. Turn ignition on, engine off. Access EVAPPF PID (PF sensor input to the PCM range is 0.40 to 4.80 volts). Turn ignition off. If EVAPPF PID voltage was greater than 4.80 volts, go to next step. If EVAPPF PID voltage was not greater than 4.80 volts, fault is an intermittent DTC P1445. Go to step 39).
  33. Step 34) Check VPWR For Short To PF Circuit In PF Sensor  Turn ignition off. Disconnect PF sensor. Allow the vehicle and PF sensor to cool down or warm up to a room temperature 55-80°F (13-27°C) before taking a resistance measurement on the PF sensor. This can take 15 to 20 minutes. Measure resistance between VPWR and PF pins on the PF sensor. See Fig 4. If resistance is 40-230 ohms, go to next step. If resistance is not 40-230 ohms, replace damaged PF sensor. Reconnect all disconnected connectors and components and go to step 42).
  34. Step 35) Check For PF Sensor Voltage Input To PCM  Turn ignition on, engine off. Measure PF circuit voltage at PF sensor harness connector to battery negative post. Turn ignition off. If voltage was greater than 10.5 volts, go to next step. If voltage was not greater than 10.5 volts, go to step 37).
  35. Step 36) Check PF Circuit For Short To VPWR  Install breakout box, leave PCM disconnected. Turn ignition on, engine off. Measure resistance between PCM test pin No.11 and PCM test pins No. 24 or 103. If the resistance is greater than 10,000 ohms, replaced damaged PCM. Reconnect all disconnected connectors and components. Repeat QUICK TEST . If the resistance is not greater than 10,000 ohms, reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST .
  36. Step 37) Check PF Circuit For Open  Install breakout box, leave PCM disconnected. Measure resistance of PF circuit between PCM test pin No. 11 and PF sensor harness connector. If the resistance is less than 5.0 ohms, go to next step. If the resistance is not less than 5.0 ohms, repair open circuit. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST .
  37. Step 38) Check PWR GND Circuit For Open  Measure resistance of PWR GND circuit between PCM test pin No. 24 or 103 and PF sensor harness connector. If the resistance is less than 5.0 ohms, replace damaged PCM. Reconnect all disconnected connectors and components. Repeat QUICK TEST . If the resistance is not less than 5.0 ohms, repair open circuit. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST .
  38. Step 39) Check PF Circuit For Intermittent Open Or VPWR Short  Turn ignition on, engine off. Access EVAPPF PID. Observe EVAPPF PID for an indication of a fault while lightly tapping on PF sensor, then wiggle PF sensor connector and harness between sensor and PCM. A fault is indicated by a sudden change in EVAPPF PID voltage (greater than 4.80 volts). If a fault is indicated, isolate fault and repair as necessary. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST . If a fault is not indicated, unable to duplicate or identify fault at this time. Go to test Z, step 1).
  39. Step 40) DTC P0443: Inspect EVAP Canister Purge Valve Circuit For Intermittent Failure  Rerun KOEO, KOER Self-Tests and retrieve Continuous Memory DTCs. If DTC P0443 is present in Continuous Memory Self-Test only, go to next step. If DTC P0443 is not present in Continuous Memory Self-Test only, go to step 1).
  40. Step 41) Check EVAP Canister Purge Valve Circuit Intermittent Open Or Short  Install breakout box, leave PCM disconnected. Measure resistance between PCM test pin No. 67 or PCM test pin No. 56 and PCM test pin No. 71, while lightly tapping on the EVAP canister purge valve and observe a resistance change. Wiggle the EVAP canister purge valve connector and vehicle harness between the valve and the PCM, observe a resistance change. If the resistance reading changes to below 30 ohms or above 90 ohms (vehicles with test pin 67) or above 38 ohms (vehicles with test pin 56), isolate fault and repair as necessary. Reconnect all disconnected connectors and components. Clear DTCs and repeat QUICK TEST . If the resistance reading does not change to below 30 ohms or above 90 ohms (vehicles with test pin 67) or above 38 ohms (vehicles with test pin 56), unable to duplicate or identify fault at this time. Go to test Z, step 1).
  41. Step 42) Verification Of EVAP Emission System Repair  Plug or tape atmospheric vent cap on EVAP canister (if applicable). Remove fuel filler cap at fuel filler pipe. Install Rotunda Evaporative Emission System Leak Tester (134-00056), including the nitrogen or argon gas supply and pressure regulator. Disconnect and plug fuel vapor hose to PF sensor from intake manifold at the intake manifold vacuum source. Pressurize the EVAP system at 27 in. H2O (6.74 kPa) with tester. Observe tester installation leak self-test for two minutes and then the EVAP system leak test. Listen for a vacuum leak noise and check for substantial fuel vapor odors at isolated areas in the EVAP system. If the pressure applied to the EVAP system holds, remove plug and reconnect fuel vapor hose from PF sensor (or EVAP canister purge valve) at intake manifold vacuum source. Remove EVAP System Leak Tester. Reinstall fuel filler cap. Tighten cap only one eighth turn so that cap initially clicks by sound or touch. Clear DTCs. Access EVAPPDC PID on scan tool. Drive vehicle (including a steady accelerator speed over 50 mph (80 km/h) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Rerun QUICK TEST  to verify a symptom no longer exists. If the pressure applied to the EVAP system does not hold, go to next step.
  42. Step 43) Check Location Of EVAP System Pressure Leak  Systematically isolate area of potential pressure leak. Close off pressure to EVAP system. Disconnect and plug fuel vapor hose from fuel tank at EVAP canister. Apply controlled pressure at 27 in. H2O (6.74 kPa) to the EVAP system with the leak tester. If pressure now holds, GO to the Powertrain/Engine Group, Evaporative Emissions Section in the Workshop Manual for EVAP canister diagnosis. If system pressure does not hold, close pressure supply to system. Disconnect and plug fuel vapor hose from EVAP canister at EVAP canister purge valve. Again, apply controlled pressure to the EVAP system. If the pressure holds, remove plugs. Reconnect fuel vapor hose at EVAP canister. Remove EVAP System Leak Tester. Reinstall fuel filler cap. Clear DTCs. Access EVAPPDC PID on scan tool. Drive vehicle (including a steady accelerator speed over 50 mph (80 km/h) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Rerun QUICK TEST  to verify a symptom no longer exists. If the pressure does not hold, remove plugs. Check for fuel vapor hose cracks or fuel vapor valve damage. Examine and secure fuel vapor hose connections to components. Repair or replace as necessary. Remove EVAP System Leak Tester. Reinstall fuel filler cap. Clear DTCs. Access EVAPPDC PID on scan tool. Drive vehicle (including a steady accelerator speed over 50 mph (80 km/h) until EVAPPDC PID shows 75 percent duty cycle). Then maintain approximate speed until duty cycle reaches zero percent. After additional two minute drive, bring vehicle to an idle. Rerun QUICK TEST  to verify a symptom no longer exists.
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