Diagnostic Aids

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).

  Transmission Control Switch (TCS) allows driver to disengage overdrive. TCS is located on transmission shift knob. The Transmission Control Switch Module (TCSM) informs PCM of drivers request to disengage overdrive and also controls the Transmission Control Indicator Light (TCIL). TCIL is located in instrument cluster.

  TEST PIN NO. 41 (TCS) WIRE COLOR IDENTIFICATION
  
  

  Application	Wire Color
  3.2L SHO	White/Light Green
  All Others	Tan/Light Green

  TEST PIN NO. 14 (TCIL) WIRE COLOR IDENTIFICATION
  
  

  Application	Wire Color
  3.2L SHO	Orange/Yellow

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

  Application	Wire Color
  All Models	Red

  NOTE: A break in step numbering sequence occurs at this point. 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 (14 on 3.2L SHO) and test pin No. 40 or 60. If each reading is more than 10 k/ohms, go to next step (Code 623 or 631) or step 8 (Code 632 or 653). If any reading is 10 k/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 (14 on 3.2L SHO) 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 (14 on 3.2L SHO) 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 Red/Yellow wire between TCS and fuse No. 18 (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 37 or 57. Also, measure resistance between test pin No. 55 (14 on 3.2L SHO) and test pin No. 37 or 57. If each reading is more than 10 k/ohms, replace TCS switch. Remove breakout box, reconnect all components, and repeat QUICK TEST  . If any reading is 10 k/ohms or less, repair short circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.