Diagnostic Aids
Perform this test when directed by QUICK TEST. This CIRCUIT TEST is intended to diagnose:
- PSOM output to ECA.
- PSOM (+) and PSOM (-) wiring harness circuits.
- ECA.
To prevent replacement of good components, be aware following non-EEC related areas and components may be cause of problem:
- Cruise control system.
- Rear anti-lock brake system.
- Instrumentation system.
CIRCUIT TEST DS TEST PIN WIRE COLOR ID
| Application | Pin No. | Wire Color |
|---|---|---|
| Aerostar | 3 (PSOM +) | Dk. Green/White |
| Except Aerostar | 3 (PSOM +) | Red/Lt. Green |
| Aerostar | 6 (PSOM -) | Black/Yellow |
| Except Aerostar | 6 (PSOM -) | Pink/Orange |
- 1) Continuous Memory Code 29/452
Code 29/452 indicates ECA detected incorrect output from VSS sometime during vehicle operation. Following are possible causes of code.
- PSOM Output To ECA
- PSOM (+) And PSOM (-) Wiring Harness Circuits
- ECA
Turn ignition off. Remove ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between test pins No. 3and 6 at breakout box. If reading is 21,000-55,000 ohms, go to step 4). If resistance is not 21,000-55,000 ohms, go to next step.
- 2) Check PSOM Circuit Continuity Ensure ignition is off. Disconnect PSOM wiring harness connector. Measure resistance between test pin No. 3 at breakout box and PSOM + circuit at PSOM wiring harness connector. If resistance is less than 5 ohms, repair open circuit and repeat QUICK TEST. If resistance is more than 5 ohms, go to next step.
- 3) Check PSOM Circuit For Open Ensure ignition is off. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If resistance is 10,000 ohms or less, repair open circuit and repeat QUICK TEST. If resistance is more than 10,000 ohms, go to next step.
- 4) Turn ignition off. Connect ECA to breakout box. Connect wiring harness connector to PSOM. Set DVOM on 20-volt AC scale. Start engine, and warm it to normal operating temperature. Measure voltage between test pins No. 3 and 6 while gradually increasing vehicle speed to 50 MPH. If maximum voltage is less than 4.5 volts, fault is in instrument cluster. If maximum voltage received is more than 4.5 volts, replace ECA.