Diagnostic Aids
WARNING: This page is about a different car, the 1995 Lincoln Mark VIII. However, it is still accessible from the selected car via links, so may be relevant.
Perform this test only when directed by QUICK TEST. This test is intended to diagnose:
- Powertrain Control Module (PCM).
- Wiring harness circuits (TCIL, TCS).
To prevent replacing good components, be aware the following non-EEC related areas may be at fault:
- Basic engine condition (valves, vacuum leaks, valve timing, etc.).
- Charging system.
- Transmission (fluid, friction elements and cooling).
Transmission Control Switch (TCS) allows driver to disengage overdrive. TCS is located on transmission shift knob. TCIL is located in instrument cluster.
TEST PIN WIRE COLOR IDENTIFICATION
| Application | Wire Color |
|---|---|
| TEST PIN NO. 41 (TCS) | Tan/Light Green |
| TEST PIN NO. 55 (TCIL) | White/Light Green |
| TEST PIN NO. 37 OR 57 (VPWR) | Red |
NOTE:
Procedure starts at step 2). No test procedures have been omitted.
- 2) Code 632 Or 653
Code 632 or 653 indicates that the TCS was not cycled between engine ID Code and WOT check during KOER SELF-TEST. Possible causes for this fault are:- Faulty TCS or switch was not cycled during SELF-TEST.
- Shorted wiring harness.
- Faulty Powertrain Control Module (PCM).
- Open in wiring harness or fuse.
If TCS was cycled during KOER SELF-TEST, go to step 4). If TCS was not cycled during KOER SELF-TEST, repeat KOER SELF-TEST while cycling TCS.
- 3) Code 623 Or 631
Code 623 or 631 indicates transmission control indicator light circuit fault during KOEO SELF-TEST. Possible causes for this fault are:- Burned out bulb.
- Open or shorted wiring harness.
If TCS was cycled during KOEO SELF-TEST, go to step 5). If TCS was not cycled during KOEO SELF-TEST, repeat KOER SELF-TEST while cycling TCS.
- 4) Check TCS Circuit
Turn ignition off. Disconnect 60-pin PCM connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 41 and test pin No. 40 or 60 at breakout box while cycling TCS several times. If voltage cycles replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST . If voltage does not cycle, go to next step if diagnosing a trouble code or step 7) if diagnosing a driveability symptom. - 5) Check Circuits For Short To Ground
Turn ignition off. Leave PCM disconnected from breakout box. Disconnect TCS connector. Inspect connector for damage and repair as necessary. Measure resistance between test pin No. 41 and test pin 40 or 60. Also, measure resistance between test pin No. 55 and test pin No. 40 or 60. If each reading is more than 10,000 ohms, go to next step (Code 623 or 631) or step 8) (Code 632 or 653). If any reading is 10,000 ohms or less, repair short circuit. Repeat QUICK TEST . If code is still present, go to step 7). - 6) Check Power Through TCIL Circuit
Turn ignition off. Leave PCM disconnected from breakout box. Measure voltage between test pin No. 55 and test pin No. 40 or 60. If voltage is more than 10.5 volts, replace PCM. Remove breakout box, reconnect all components, and repeat QUICK TEST . If voltage is 10.5 volts or less, go to next step. - 7) Check Output Driver Voltage Signal
Leave PCM disconnected from breakout box. Turn ignition on. Measure voltage between test pin No. 55 and test pin No. 40 or 60. If voltage is 2 volts or more, go to next step. If voltage is less than 2 volts, check bulb and fuse. Replace as necessary. If bulb and fuse are okay, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST . - 8) Check Transmission Control Switch Wiring Harness
Turn ignition off. Leave PCM disconnected from breakout box. Ensure TCS is disconnected. Measure resistance of Red/Yellow wire between TCS and fuse No. 9 (10-amp) at instrument panel fuse block. Measure resistance of TCS circuit between test pin No. 41 at breakout box and TCS circuit terminal at TCS wiring harness connector. If any reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST . If each reading is less than 5 ohms, go to next step. - 9) Check For Short To Power
Turn ignition off. Leave PCM disconnected from breakout box. Ensure TCS is disconnected. Measure resistance between test pin No. 41 and test pin No. 37 or 57. Also, measure resistance between test pin No. 55 and test pin No. 37 or 57. If each reading is more than 10,000 ohms, replace TCS switch. Remove breakout box, reconnect all components, and repeat QUICK TEST . If any reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST .