Code P090, TCC Brake Switch Input Circuit Problem: Action

PCM turns on SERVICE VEHICLE SOON message. PCM disables cruise control.

NOTE: Test numbers refer to numbers on diagnostic chart.

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.
Checks for voltage at TCC brake switch terminal "A".

Fig 1: Code P090 Schematic (DeVille)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P090 Flow Chart (DeVille)

Courtesy of GENERAL MOTORS CORP.