Code P088, TCC Not Disengaging: Action

PCM turn on MIL and freezes shift adapts from being updated. TCC disabled.

PCM turn on MIL.

1. Tests TCC brake switch input to PCM data PI71. If input is working properly, display will change from HI to LO to HI. If input is not working properly, display will not change.
2. Checks circuit No. 422 for short to ground inside transaxle.
3. Checks PCM's ability to control PCM output PO02. Voltage will cycle between zero and 12 volts if PCM is okay.
4. Checks circuit No. 422 for short to ground between TCC solenoid connector and PCM.
5. Check for short to voltage in TCC control circuit if PI71 stays HI. Check circuit No. 741 for open or circuit No. 420 for open or short if PI71 stays LO.
6. Possible hydraulic problem when TCC applies when not electrically commanded.

Fig 1: Codes P088 Schematic (4.6L)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Codes P088 Flow Chart (4.6L)

Courtesy of GENERAL MOTORS CORP.