Diagnostic Aids

WARNING: This page is about a different car, the 1995 Ford Ranger. 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:

Canister Purge (CANP) solenoid.
Purge Flow Sensor (PFS).
Carbon canister.
Leaks in fuel tank, filler cap or vapor hoses.
Wiring harness circuits (CANP SIG, PFS SIG, PWR GND, VMV SIG and VPWR).
Faulty Powertrain Control Module (PCM).

Fig 1: Identifying EVAP System Components (Ranger)

Fig 2: Identifying CANP System Test Circuit (Ranger)

Fig 3: Identifying PFS System Test Circuit (Ranger)

1) DTC P0443: Check VPWR Circuit Voltage

Disconnect CANP or VMV solenoid wiring harness connector. Turn ignition on. Measure voltage between VPWR terminal of solenoid 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) Check Solenoid Resistance

Turn ignition off. Leave solenoid wiring harness connector disconnected. Measure resistance between connector terminals. If resistance is 30-90 ohms, go to step 3). If resistance is not as specified, replace CANP or VMV solenoid. Clear PCM memory and repeat QUICK TEST .

3) Check VMV Circuit Continuity

Turn ignition off. 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 between test pin No. 56 (VMV) and VMV terminal of VMV wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in VMV circuit. Clear PCM memory and repeat QUICK TEST .

4) Check VMV Circuit For Short To PWR GND

Leave ignition off. Disconnect scan tester from DLC (if applicable). Measure resistance between test pin No. 56 and test pins No. 24 and 103. If each resistance is more than 10,000 ohms, replace PCM and repeat QUICK TEST . If any resistance is 10,000 ohms or less, repair short to ground in VMV circuit. Clear PCM memory and repeat QUICK TEST .

5) 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 is indicated, isolate and repair as necessary. If no fault is indicated, go to next step.

6) Check Carbon Canister

Vehicle must have been operated for a period of time equivalent to a drive cycle to purge all fuel vapors. Check for cracks or damage to canister. Repair or replace as necessary. If canister is okay, go to next step.

7) Check EVAP System Vacuum

Remove fuel vapor hose from fuel tank at canister. Attach vacuum pump with gauge to vacuum hose. Using vacuum pump, apply 1.0 in. Hg to fuel vapor hose. If system holds vacuum, go to next step. If system will not hold vacuum, isolate leak and repair as necessary.

8) Check vacuum hose between fuel tank and carbon canister for faults. Check for fuel tank damage. Check for damaged orifice rollover valve. Repair or replace as necessary. If no faults are found, remove vacuum pump and go to next step.

9) Check VMV Vacuum

Turn ignition off. Disconnect vacuum hose from carbon canister and VMV (manifold side). Plug either end of hose. Using a vacuum pump, apply 16 in. Hg to opposite end of hose. If vacuum is held for 15 seconds, release vacuum from solenoid and go to step 15). If vacuum is not held for 15 seconds, replace fuel vapor hose and repeat QUICK TEST .

10) Check CANP Solenoid For Vacuum Leaks

Turn ignition off. Disconnect vacuum hose from CANP solenoid. Disconnect wiring harness connector. Using a vacuum pump, apply 16 in. Hg to solenoid. If vacuum is held for 20 seconds, leave pump connected and go to next step. If vacuum is not held for 20 seconds, replace CANP solenoid and repeat QUICK TEST .

11) Check CANP Solenoid Mechanical Operation

Turn ignition off. Disconnect vacuum hose at both ends of CANP solenoid. Reconnect wiring harness connector. Ensure scan tester is connected to DLC. Using a vacuum pump, apply 16 in. Hg to solenoid intake manifold port. Using scan tester, access Output Test Mode. Turn ignition on. If CANP solenoid does not open (air passes freely) when output is commanded on, replace CANP solenoid and repeat QUICK TEST . If CANP solenoid does open when output is commanded on, check vapor hose between carbon canister and CANP solenoid and repair if necessary. If vapor hose is okay, go to next step.

12) Check Vacuum At CANP Solenoid

Turn ignition off. Disconnect CANP solenoid and Purge Flow Sensor (PFS). Ensure vacuum hose is disconnected from CANP solenoid intake manifold port. Start engine and allow to idle. Check for vacuum at CANP terminal. If vacuum is present, go to next step. If vacuum is not present, check vacuum hoses and PFS. Repair or replace as necessary and repeat QUICK TEST .

13) Check PFS Seal

Turn ignition off. Leave PFS wiring harness connector disconnected. Plug open end of vacuum hose at CANP solenoid. Disconnect PFS vacuum hose at intake manifold port. Using a vacuum pump, apply 4.1 in. Hg to intake manifold port. If vacuum bleeds off in less than 2.5 seconds, replace PFS and repeat QUICK TEST . If vacuum does not bleed off in less than 2.5 seconds, remove vacuum pump and reconnect hose to CANP solenoid. Leave vacuum hose disconnected from PFS and go to next step.

14) Check Vacuum At PFS

Turn ignition off. Disconnect CANP solenoid and Purge Flow Sensor (PFS). Ensure vacuum hose is disconnected from PFS solenoid intake manifold port. Start engine and allow to idle. Check for vacuum at PFS terminal. If vacuum is present, go to step19). If vacuum is not present, check for excessive wear causing vacuum loss. If engine is okay, go to TESTS W/O CODES - EEC-V article.

15) Check VMV

Turn ignition off. Reconnect VMV wiring harness connector. Disconnect vacuum hose from intake manifold port at VMV. Attach vacuum pump with gauge to intake manifold port at VMV. See Fig 4 . Using vacuum pump, apply 16 in. Hg to VMV. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, cycle outputs on and off. VMV should open and release vacuum when scan tester output is commanded on. If VMV functions as specified, go to next step. If VMV does not function as specified, replace VMV and repeat QUICK TEST .

Fig 4: VMV Solenoid Vacuum Hose Terminal ID (Ranger)

16) Check VMV Housing

Turn ignition off. Ensure VMV wiring harness connector is connected. Disconnect vacuum input hose from VMV. Using a vacuum pump, apply 16 in. Hg to VMV. If vacuum bleeds off immediately, go to next step. If vacuum is not bled off immediately, replace VMV and repeat QUICK TEST .

17) Check Vacuum At VMV Vacuum Input Port

Turn ignition off. Leave vacuum input hose from VMV disconnected. Start engine and allow to idle. Check for vacuum at open end of vacuum hose. If vacuum is present, reconnect hose and go to next step. If vacuum is not present, check VMV vacuum input hose for blockage or leaks and repair or replace as necessary.

18) Check Vacuum At VMV Vacuum Input Port

Turn ignition off. Disconnect intake manifold port hose from VMV. Start engine and allow to idle. Check for vacuum at open end of vacuum hose. If vacuum is present, reconnect hose and go to next step. If vacuum is not present, check VMV vacuum input hose for blockage or leaks and repair or replace as necessary.

19) Check CANP Or VMV Resistance

Turn ignition off. Disconnect CANP or VMV wiring harness connector. Measure resistance between CANP or VMV terminals. If resistance is 30-90 ohms for CANP solenoid or 30-36 ohms for VMV, go to next step. If resistance is not as specified, replace CANP solenoid or VMV. Clear PCM memory and repeat QUICK TEST .

20) Check CANP Or VMV Circuit For Short To VPWR

Leave ignition off and CANP or VMV disconnected. Disconnect PCM wiring harness connector. Inspect pins for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Disconnect scan tester (if applicable). Measure resistance between test pin No. 56 and test pins No. 71 and 91. If each resistance is more than 10,000 ohms, replace PCM and repeat QUICK TEST . If any resistance is 10,000 ohms or less, repair CANP or VMV circuit short to VPWR. Clear PCM memory and repeat QUICK TEST .

21) Continuous Memory DTC P1444

Turn ignition off. Connect scan tester to Diagnostic Link Connector (DLC). Turn ignition on. Using scan tester, access PF PID. If PF PID voltage is less than 0.14 volt, go to next step. If voltage is 0.14 volt or more, go to step 24).

22) Turn ignition off. Disconnect PFS wiring harness connector. Measure resistance between terminal No. 2 and No. 3. See Fig 5 . If resistance is less than 25.5 ohms, replace PFS sensor and repeat QUICK TEST . If resistance is 25.5 ohms or more, go to step 31).

Fig 5: PFS Sensor Connector Terminal ID (Ranger)

23) Check VMV Circuit For Short To VPWR

Leave ignition off and PFS disconnected. Disconnect PCM wiring harness connector. Inspect pins for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Disconnect scan tester (if applicable). Measure resistance between breakout box test pin No. 11 and test pins No. 24 and 103. If each resistance is more than 10,000 ohms, replace PCM and repeat QUICK TEST . If any resistance is 10,000 ohms or less, repair PFS circuit short to PWR GND. Clear PCM memory and repeat QUICK TEST .

24) Wiggle Test Solenoid & Harness

Turn ignition off. Using scan tester, access PF PID. Observe PF PID for indication of fault while shaking and bending PFS wiring harness and connector. A fault will be indicated by sudden change of voltage. Tap lightly on PFS sensor to simulate road shock. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to CIRCUIT TEST Z.

25) Continuous DTC P1445

Turn ignition off. Connect scan tester to Diagnostic Link Connector (DLC). Turn ignition on. Using scan tester, access PF PID. If PF PID voltage is more than 4.89 volts, go to next step. If voltage is 4.89 volts or more, go to step 33).

26) Turn ignition off. Disconnect PFS wiring harness connector. Measure resistance between terminal No. 1 and No. 2. See Fig 5 . If resistance is 25.65-28.35 ohms, go to next step. If resistance is not 25.65-28.35 ohms, replace PFS sensor and repeat QUICK TEST .

27) Check PFS Circuit Short To VPWR

Leave PFS sensor disconnected. Turn ignition on. Measure voltage between PFS terminal of sensor 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, go to step 29).

28) Turn ignition off. Leave PFS sensor disconnected. Disconnect PCM wiring harness connector. Inspect pins for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin No. 11 and test pins No. 24 and 103. If voltage is greater than 10.5 volts, repair PFS circuit short to VPWR and repeat QUICK TEST . If voltage is 10.5 volts or less, replace PCM and repeat QUICK TEST .

29) Turn ignition off. Leave PFS sensor 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 between breakout box test pin No. 11 and PFS terminal at 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 PFS circuit. Clear PCM memory and repeat QUICK TEST .

30) Leave ignition off and PFS sensor disconnected. Measure resistance between breakout box test pins No. 24 and 103. If resistance is less than 5 ohms, replace PCM and repeat QUICK TEST . If resistance is 5 ohms or more, repair open in PWR GND circuit and repeat QUICK TEST .

31) Leave ignition off and PFS sensor disconnected. Measure resistance between terminal No. 1 and No. 2. See Fig 5 . Measure resistance between terminal No. 1 and No. 3. If resistance is greater than 100 ohms between terminal No. 1 and No. 2, and greater than 130 ohms between terminal No. 1 and No. 3, replace PFS sensor and repeat QUICK TEST . If resistance is not as specified, go to next step.

32) Leave ignition off and PFS sensor disconnected. Measure resistance between breakout box test pins No. 71 and No. 97. Measure resistance between breakout box test pin No. 71 and VPWR terminal at PFS sensor wiring harness connector. If resistance is less than 5 ohms, return to step 23). If resistance is 5 ohms or more, repair open in VPWR circuit. Clear PCM memory and repeat QUICK TEST .

33) Continuous Memory DTC P0443: Check VMV Circuit For Intermittent Failure

Repeat QUICK TEST . If Continuous Memory DTC P0443 is still present, go to next step. If Continuous Memory DTC P0443 is not present, fault is intermittent and cannot be duplicated at this time. Testing is complete.

34) Wiggle Test Solenoid & Harness

Turn ignition off. Disconnect PCM wiring harness connector. Inspect pins for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Using DVOM, measure resistance between test pin No. 56 and test pins No. 71 and 91. Observe DVOM for indication of fault while shaking and bending VMV wiring harness and connector. A fault will be indicated by resistance measurement of less than 30 ohms or more than 36 ohms. Tap lightly on VMV to simulate road shock. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to CIRCUIT TEST Z.