Code P026, Shorted Throttle Position Switch Circuit: Action

PCM turns on MIL, disables EGR and assumes throttle switch is closed if brakes are applied or if TP sensor position is less than or equal to 18 degrees. PCM also assumes open throttle when brakes are off or TP sensor position is greater than 18 degrees. Garage shift adapts are maintained at current levels.

1. PCM input PI72 should cycle from LO to HI to LO when accelerator is depressed and released.
2. If PCM input PI72 changes to HI when ISC motor is disconnected, fault is with ISC motor. If PI72 still stays LO, check circuit No. 427 for short to ground.
3. Checks if circuit No. 427 is shorted to ground or if PCM is faulty.

Fig 1: Code P026 Schematic, Shorted Throttle Position Switch Circuit

Courtesy of GENERAL MOTORS CORP

Fig 2: Code P026 Diagnostic Flow Chart, Shorted Throttle Position Switch Circuit

Courtesy of GENERAL MOTORS CORP