Diagnostic Aids

WARNING: This page is about a different car, the 1996 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:

Generic electronic module wiring harness circuits.
Powertrain Control Module (PCM).

Fig 1: Generic Electronic Module Test Circuit & Connector Terminals

Step 1) DTC P1729 & P1781 DTC P1729 indicates 4x4 switch open or short circuit. DTC P1781 indicates 4x4L switch position closed during QUICK TEST . If switch position was not 4x2 or 4x4H during KOEO SELF-TEST , select 4x2 or 4x4H and repeat QUICK TEST . If switch position was as specified, go to next step.
Step 2) Check Intermittent Circuit Failure Turn ignition off. Connect scan tester to DLC. Using scan tester, access 4x4L PID. Turn ignition on. Cycle switch to 4x2. Shake and bend sections of wiring harness between generic electronic module and transfer case wiring harness connector. Shake and bend sections of wiring harness between generic electronic module PCM. Tap wiring harness connector to simulate road shock. If scan tester voltage fluctuates, isolate fault and repair as necessary. If scan tester voltage does not fluctuate, go to next step.
Step 3) Check Signal From PCM Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Turn ignition on. While cycling switch, measure voltage between breakout box test pin No. 14 and No. 24 (PWR GND). If voltage cycles, replace PCM and repeat QUICK TEST . If voltage does not cycle, go to next step.
Step 4) Check Circuit Continuity Turn ignition off. Disconnect generic electronic module. Inspect pins for damage and repair if necessary. Measure resistance between breakout box test pin No. 14 and Yellow/Black wire terminal at generic electronic module wiring harness connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open circuit and repeat QUICK TEST .
Step 5) Check For Short To Power Or Ground Leave ignition off. Reconnect generic electronic module. Measure resistance between breakout box test pin No. 14 and No. 24. If resistance is more than 10,000 ohms, repair transfer case mechanical fault. If resistance is 10,000 ohms or less, repair short circuit and repeat QUICK TEST .