Diagnostic Aids

WARNING: This page is about a different car, the 1994 Mercury Sable, 1994 Mercury Cougar, 1994 Lincoln Continental, 1994 Ford Thunderbird, and 1994 Ford Taurus. 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 and TCSM).

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).

TEST PIN NO. 41 (TCS) WIRE COLOR IDENTIFICATION

Application	Wire Color
All Models	Tan/Light Green

TEST PIN NO. 14 OR 55 (TCIL) WIRE COLOR ID ⁽¹⁾

Application

Wire Color

Cougar & Thunderbird

Except Supercharged

Tan/Light Green

Supercharged

Tan/White

⁽¹⁾	TCIL circuit is pin No. 55.

TEST PIN NO. 37 OR 57 (VPWR) WIRE COLOR ID

Application	Wire Color
All Models	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 cycled during KOER SELF-TEST, go to step 4). If TCS did not cycle 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 cycled during KOEO SELF-TEST, go to step 5). If TCS did not cycle 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 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 TCS & TCIL Circuits Turn ignition off. Leave PCM disconnected from breakout box. Ensure TCS is disconnected. Measure resistance of Purple/Orange wire between KEY POWER terminal of fuse No. 1 at instrument panel fuse block and TCS wiring harness connector. Also, measure resistance between test pin No. 41 at breakout box and Purple/Orange wire 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.