Code P090, TCC Brake Switch Input Circuit Problem: Action

Traction control disabled. PCM disables cruise control and substitutes status of stop/BTSI/cruise brake switch input for TCC brake switch input. "TRACTION DISABLED" and "REDUCED ENGINE POWER" message displayed on DIC. Garage shift adapts are maintained at current levels.

1. Testing TCC brake switch input to PCM PI71. If input is working correctly, display will change from HI to LO to HI. If display remains HI, check circuit No. 420 and TCC brake switch for short to voltage. If display remains LO, check circuit No. 420 for open or short to ground.
2. Checks for voltage at TCC brake switch terminal "A".
3. Checks circuit No. 741 for short to ground.
4. Checks circuit No. 420 for short to ground. If circuit is okay, check circuit No. 741 for open.
5. Checks circuit No. 420 for open.

Fig 1: Code P090 Schematic, TCC Brake Switch Input Circuit Problem

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P090 Diagnostic Flow Chart, TCC Brake Switch Input Circuit Problem

Courtesy of GENERAL MOTORS CORP.