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. Some vehicles may not have power steering, but PCM may be equipped with PSP switch software strategy. If a KOEO DTC P1650 or P1651 is displayed, check if vehicle is equipped with power steering. If vehicle is not equipped with power steering, disregard DTC P1650 or P1651. This test is only intended to diagnose:

* Wiring harness circuits (SIG RTN and PSP).

* PSP switch.

* Powertrain Control Module (PCM).

Fig 1: Identifying PSP Test Circuit & Connector Terminals

1) DTC P1650 Or P1651

DTC P1650 indicates PSP signal is out of self-test range. DTC P1651 indicates PSP signal malfunction. Possible causes for this fault are as follows:

* Open or short in wiring harness.

* Faulty PSP switch.

* Faulty Powertrain Control Module (PCM).

Start engine and allow to idle. Using scan tester, access PSP PID (if scan tester cannot access PSP PID, go to next step). Turn steering wheel left, then right. If scan tester does not indicate on/off switching, go to next step. If scan tester indicates on/off switching, go to CIRCUIT TEST Z.

2) Check PSP Switch Operation

Turn ignition off. Install tachometer. Start engine and allow to idle. Disconnect PSP switch. If engine speed increases when switch is disconnected, replace switch and repeat QUICK TEST . If engine speed does not increase when switch is disconnected, go to next step.

3) Check PSP Circuit Continuity

Turn ignition off. Leave PSP switch disconnected. Turn ignition off. Disconnect 104-pin PCM connector. Inspect connector for damage and repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 91 (SIG RTN) at breakout box and SIG RTN terminal of PSP switch connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST .

4) Check For Short In PSP Circuit

Leave ignition off and PSP switch disconnected. Measure resistance between test pin No. 31 (PSP) and 91 at breakout box. Measure resistance between test pin No. 31 and chassis ground. If both resistance measurements are 10,000 ohms or more, replace PCM and repeat QUICK TEST . If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST .