Pcm Code P026 - Shorted Throttle Switch Circuit: Action

PCM turns on SERVICE ENGINE SOON light, 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 more than 18 degrees.

1. PCM input P172 should cycle from LO to HI to LO when accelerator is depressed and released.
2. If PCM input P172 changes to HI when ISC motor is disconnected, fault is with ISC motor. If P172 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: PCM Code P026 Schematic - Shorted Throttle Switch Circuit

Courtesy of GENERAL MOTORS CORP.

Fig 2: PCM Code P026 Flow Chart - Shorted Throttle Switch Circuit

Courtesy of GENERAL MOTORS CORP.