Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

• Wiring harness circuits (TCIL and TCS).
• Faulty Powertrain Control Module (PCM).
  Fig 1: TCIL & TCS Circuit Schematic

  

1. DTC P1780
   
   This code indicates that TCS was not cycled during KOER SELF-TEST. Possible causes are as follows:
   • TCS not cycled during KOER SELF-TEST.
   • TCS circuit damage.
   • Faulty TCS.
   • Faulty PCM.

   Repeat KOER SELF-TEST if TCS was not cycled in original test. If TCS was cycled during KOER SELF-TEST, go to next step.

2. Check TCS Circuit Voltage
   
   Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage. Install EEC-V Breakout Box (014-00959), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 29 (TCS) and test pins No. 24 and 77 (PWR GND) at breakout box while cycling TCS. If voltmeter reading does not cycle when TCS is cycled, go to next step. If voltmeter reading cycles when TCS is cycled, replace PCM and repeat QUICK TEST  .
3. Check Circuit For Short To Ground
   
   Turn ignition off. Disconnect TCS. Inspect pins for damage and repair if necessary. Measure resistance between breakout box test pin No. 29 (TCS) and test pins No. 24 and 77 (PWR GND). If resistance is 10,000 ohms or more, go to next step. If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST  .
4. Check Continuity Of TCS Circuits
   
   Leave ignition off. Connect ohmmeter positive lead to TCS keypower at the fuse panel. Connect negative lead to power terminal of TCS wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST  .
5. Check Circuit For Short To Power
   
   Leave ignition off. Measure resistance between breakout box test pin No. 29 (TCS) and test pins No. 71 and 97 (VPWR). If resistance is 10,000 ohms or more, replace TCS switch and repeat QUICK TEST  . If resistance is less than 10,000 ohms, repair short circuit and repeat QUICK TEST  .
6. TCIL Always On
   
   Turn ignition on. Cycle TCS. If TCIL does not cycle on and off, go to next step. If TCIL cycles on and off, fault is intermittent. Go to CIRCUIT TEST Z  .
7. Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Turn ignition on. If TCIL goes off, replace PCM. If TCIL remains on, repair TCIL circuit short to ground.
8. TCIL Will Not Turn On
   
   Perform KOER SELF-TEST  . If DTC 1780 is not present, go to next step. If DTC 1780 is present, go to step 1).
9. Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-00959), leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 79 (TCIL) and test pins No. 24 and 76 (PWR GND) at breakout box. If voltage is 2 volts or more, replace PCM. If voltage is less than 2 volts, check indicator bulb and fuse. If bulb and fuse are okay, repair open circuit between test pin No. 79 and ignition switch.