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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 by QUICK TEST . This test is only intended to diagnose:

Fig 1: EGR Vacuum Regulator Solenoid Connector Terminals
G95I35988
Fig 2: EGR Position (EVP) Sensor Connector Terminals
G95J35989
  1. Step 1) DTC P1400: Check EGRVP Voltage  This code indicates open in DPFE SIG circuit. Possible causes for this fault are:
    • EVP circuit shorted to GND or SIG RTN circuit.
    • Open in EVP or VREF circuit.
    • Faulty EGR Valve Position (EVP) sensor.
    • Faulty PCM.

    Turn ignition off. Connect scan tester to DLC. Turn ignition on. Using scan tester, access EGRVP PID. If voltage is less than 0.2 volt, go to next step. If voltage is 0.2 volt or more, go to step 6).

  2. Step 2) Generate Opposite DPFE Signal  Turn ignition off. Disconnect EVP sensor wiring harness connector. Using a jumper wire, connect EVP terminal and VREF terminals at wiring harness connector. Turn ignition on. Using scan tester, access EGRVP PID. If scan tester error occurs, disconnect jumper wire and go to step 3). If EGRVP PID value is not 4-6 volts, go to next step. If EGRVP PID value is 4-6 volts, replace EVP sensor and repeat QUICK TEST .
  3. Step 3) Measure VREF Voltage At DPFE Sensor  Leave EVP sensor disconnected. Turn ignition on. Measure voltage between SIG RTN terminal and VREF terminal at EVP wiring harness connector. If voltage is 4-6 volts, go to step 4). If voltage is not 4-6 volts, go to CIRCUIT TEST C.
  4. Step 4) Check EVP Circuit Continuity  Leave ignition off and EVP sensor disconnected. Disconnect PCM 104-pin connector. Inspect for damaged pins and repair if necessary. Connect EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 63 (EVP) and EVP terminal at EVP sensor wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in EVP circuit and repeat QUICK TEST .
  5. Step 5) Check EVP Circuit For Short To PWR GND Or SIG RTN  Leave EVP sensor disconnected. Turn ignition off. Measure resistance between test pin No. 63 (EVP) and test pins No. 91 (SIG RTN), 51 and 103 (PWR GND). If each measurement is 10,000 ohms or more, replace PCM and repeat QUICK TEST . If any measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST .
  6. Step 6) Wiggle Test Sensor & Harness  With ignition off, connect scan tester to DLC. Turn ignition on. Access EGRVP PID with scan tester. Observe EGRVP PID for indication of fault while shaking and bending EVP sensor wiring harness and connector. Tap lightly on EVP sensor to simulate road shock. An indication of fault is a sudden change in EVRVP PID voltage. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 10). No test procedures have been omitted.
  7. Step 10) DTC P1401: Check EVPVP PID Voltage  This code indicates PCM has detected EVP circuit input above maximum. Possible causes for this fault are:
    • Open in SIG RTN circuit.
    • EVP circuit shorted to VREF or PWR circuit.
    • Faulty EVP sensor.
    • Faulty PCM.

    With ignition off, connect scan tester to DLC. Turn ignition on. Access EVPVP PID. If voltage is more than 4.0 volts, go to next step. If voltage is 4.0 volts or less, go to step 15).

  8. Step 11) Check EVP SIG For Short To Power  Turn ignition off. Disconnect EVP wiring harness connector. Turn ignition on. Measure voltage between EVP terminal at wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, go to step 13).
  9. Step 12) Leave ignition off and EVP sensor disconnected. Disconnect PCM 104-pin connector. Inspect for damaged pins and repair if necessary. Connect EEC-V Breakout Box (014-000950), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 63 (EVP) and test pins No. 51 and 103 (PWR GND) at breakout box. If voltage is 10.5 volts or more, repair short between EVP and PWR circuit. Repeat QUICK TEST . If voltage is less than 10.5 volts, replace PCM and repeat QUICK TEST .
  10. Step 13) Verify VREF Is Within Range  Leave EVP sensor disconnected. Turn ignition on. Measure voltage between SIG RTN terminal and VREF terminal at EVP wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.
  11. Step 14) Generate Opposite EVP Signal  Turn ignition off. Leave EVP sensor disconnected. Turn ignition on. Using scan tester, access EGRVP PID. If EGRVP PID value is .05 volt or more, replace PCM and repeat QUICK TEST . If EGRVP PID value is less than .05 volt, replace EVP sensor and repeat QUICK TEST .
  12. Step 15) Wiggle Test Sensor & Harness  With ignition off, connect scan tester to DLC. Turn ignition on. Access EGRVP PID with scan tester. Observe EGRVP PID for indication of fault while shaking and bending EVP sensor wiring harness and connector. Tap lightly on EVP sensor to simulate road shock. An indication of fault is a sudden change in EVRVP PID voltage. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 20). No test procedures have been omitted.
  13. Step 20) DTC P1409  This code indicates self-test has detected electrical malfunction in EVR circuit. Possible causes are as follows:
    • EVR circuit open or shorted.
    • Faulty EGR Vacuum Regulator (EVR) solenoid.
    • Faulty PCM.

    Turn ignition off. Disconnect EVR solenoid wiring harness connector. Measure resistance across EVR solenoid terminals. If resistance is 26-40 ohms, go to next step. If resistance is not 26-40 ohms, replace EVR solenoid. Clear PCM memory and repeat QUICK TEST .

  14. Step 21) Check VPWR To EVR Solenoid  Leave EVR solenoid wiring harness connector disconnected. Turn ignition on. Measure voltage between VPWR terminal at EVR solenoid wiring harness connector and chassis ground. If voltage 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, repair open in VPWR circuit. Clear PCM memory and repeat QUICK TEST .
  15. Step 22) Check EVR Circuit Continuity  Turn ignition off. Leave EVR solenoid disconnected. Disconnect PCM 104-pin connector. Inspect for damage pins and repair if necessary. Connect EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 47 (EVR) and EVR terminal at EVR solenoid wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in EVR circuit. Clear PCM memory and repeat QUICK TEST .
  16. Step 23) Check EVR Circuit For Short To Power Or VREF  Leave EVR solenoid disconnected. Turn ignition on. Measure voltage between test pin No. 47 (EVR) and test pins No. 51 and 103 (PWR GND) at breakout box. If each measurement is less than one volt, go to next step. If any measurement is one volt or more, repair circuit short and repeat QUICK TEST .
  17. Step 24) Check EVR Circuit For Short To Ground  Leave EVR solenoid disconnected. Turn ignition off. Measure resistance between test pin No. 47 and test pins No. 51 and 103 (PWR GND) at breakout box. If resistance is 10,000 ohms or more, go to next step. If any measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST .
  18. Step 25) Wiggle Test Solenoid & Harness  With ignition off, reconnect EVR solenoid connector. Turn ignition on. Measure voltage between test pin No. 47 and test pins No. 51 and 103 (PWR GND) at breakout box. Voltage should be 10.5 volts or more. Observe voltmeter for indication of fault while shaking and bending EVR solenoid wiring harness and connector. An indication of fault is a sudden change in voltage. Tap lightly on EVR solenoid to simulate road shock. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 25) to step 30). No test procedures have been omitted.
  19. Step 30) DTC P0401: Check EGR Solenoid Vacuum  This code indicates self-test has detected insufficient EGR flow. Possible causes are as follows:
    • Faulty vacuum hoses.
    • Faulty EGR Valve Position (EVP) sensor.
    • Faulty EGR Vacuum Regulator (EVR) solenoid.

    Turn ignition off. Disconnect EVR solenoid vacuum supply hose. Install vacuum gauge at unattached end of disconnected vacuum hose. Start engine and allow to idle. If vacuum gauge indicates 10 in. Hg or more, remove vacuum gauge and go to next step. If vacuum gauge indicates less than 10 in. Hg, repair vacuum restriction as necessary and repeat QUICK TEST .

  20. Step 31) Turn ignition off. Check EGR vacuum supply hose. If hose is okay, go to next step. If hose is not okay, repair as necessary and repeat QUICK TEST .
  21. Step 32) Check EGR Valve  Leave ignition off. Plug EGR vacuum supply hose. Disconnect IAC solenoid wiring harness connector. Start engine and allow to idle. Using vacuum pump, slowly apply 10 in. Hg to EGR valve and then release. If engine speed drops more than 100 RPM with vacuum applied and then returns to idle with vacuum removed, go to next step. If vacuum is not as specified, repair or replace EGR valve and repeat QUICK TEST .
  22. Step 33) Check EGRVP PID  Turn ignition off. Reconnect IAC solenoid. Connect scan tester to DLC. Turn ignition on. Using scan tester, access EGRVP PID. With EGR valve closed, EGRVP PID should be 0.24-0.67 volts. Using vacuum pump, slowly apply 10 in. Hg to EGR valve. With EGR valve open, EGRVP PID should be more than 3.0 volts. If EGRVP PID is as specified, go to next step. If EGRVP PID is not as specified, replace EVP sensor and repeat QUICK TEST .
  23. Step 34) Check EVR Solenoid Operation  Turn ignition off. Leave EGR vacuum supply hose connected to vacuum gauge. Disconnect PCM 104-pin connector. Inspect for damage pins and repair if necessary. Connect EEC-V Breakout Box (014-000950) to PCM connector. Connect PCM to breakout box. Start engine and allow to idle. Connect jumper wire between test pin No. 47 and test pin No. 51 or 103 (PWR GND) at breakout box. Vacuum gauge should indicate 5.0 in. Hg or more. If vacuum is as indicated, leave jumper wire connect and go to next step. If vacuum is not as indicated, replace EVR solenoid and repeat QUICK TEST .
  24. Step 35) Wiggle Test Solenoid & Harness  With engine idling, observe vacuum gauge for indication of fault while shaking and bending EVR solenoid wiring harness and connector. An indication of fault is sudden drop in vacuum. Tap lightly on EVR solenoid to simulate road shock. If fault indicated, isolate/repair as necessary. If no fault indicated, problem intermittent, cannot be duplicated at this time. Go to CIRCUIT TEST Z.
    NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 35) to step 40). No test procedures have been omitted.
  25. Step 40) DTC P0402  This code indicates EGR flow has been detected during self-test. Possible causes are as follows:
    • Restricted vacuum hoses.
    • EVR circuit shorted to ground.
    • Faulty EGR valve.
    • Faulty EGR Valve Position (EVP) sensor.
    • Faulty EGR Vacuum Regulator (EVR) solenoid.
    • Faulty PCM.

    Repeat QUICK TEST . If DTC P1409 is present, go to step 20). If DTC P1409 is not present, go to next step.

  26. Step 41) Check EGRVP PID  Turn ignition off. Connect scan tester to DLC. Turn ignition on. Using scan tester, access EGRVP PID. With EGR valve closed, EGRVP PID should be 0.24-0.67 volts. If EGRVP PID is less than 0.67 volts, go to step 44). If EGRVP PID is 0.67 volts or more, go to next step.
  27. Step 42) Leave ignition on. Disconnect EGR vacuum supply hose. With EGR valve closed, EGRVP PID should be 0.24-0.67 volts. If EGRVP PID is now as specified, check vacuum hoses for restrictions. If hoses are okay, replace EVR solenoid and repeat QUICK TEST . If EGRVP PID is not as specified, go to next step.
  28. Step 43) Check EGR Valve  Leave ignition off. Disconnect EGR vacuum supply hose. Connect vacuum pump to EGR valve. Start engine and allow to idle. Using scan tester, access EGRVP PID. Using vacuum pump, slowly apply 10 in. Hg to EGR valve and then release several times. If EGRVP PID returns to 0.24-0.67 volts, check EGR valve for binding or contamination and repair as necessary. If EGRVP PID does not return to 0.24-0.67 volts, check EGR valve and EVP sensor for damage and repair as necessary. Repeat QUICK TEST .
  29. Step 44) Check EGRVP PID  Leave scan tester connected to DLC. Start engine and allow to idle. Using scan tester, access EGRVP PID. At idle speed, EGRVP PID should be 0.24-0.67 volts. If EGRVP PID is less than 0.67 volts, go to step 46). If EGRVP PID is 0.67 volts for more, fault is indicated; go to next step.
  30. Step 45) Turn ignition off. Remove EVR solenoid vent cap. Inspect vent for restriction and repair if necessary. Ensure vacuum hoses are in good condition and routed properly. If hoses are okay, go to next step. If hoses not okay, repair as necessary and repeat QUICK TEST .
  31. Step 46) Check EGR System For Intermittent Fault  Turn ignition off. Disconnect EGR vacuum supply hose. Connect vacuum pump to EGR valve. Start engine and allow to idle. Using scan tester, access EGRVP PID. Using vacuum pump, slowly apply 10 in. Hg to EGR valve and then release several times. If EGRVP PID returns to 0.24-0.67 volts, go to next step. If EGRVP PID does not return to 0.24-0.67 volts, isolate and repair as necessary. Repeat QUICK TEST .
  32. Step 47) Wiggle Test EVP Sensor & EVR Solenoid  Using scan tester, access EGRVP PID. With engine idling, EGRVP PID for indication of fault while shaking and bending EVR solenoid wiring harness and connector. An indication of fault is a sudden increase in voltage above 0.67 volts. Tap lightly on EVP sensor and EVR solenoid to simulate road shock. If fault is indicated, isolate and repair as necessary. If no fault indicated, problem is intermittent, cannot be duplicated at this time. Go to CIRCUIT TEST Z.
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