Code P026, Shorted Throttle Position Switch Circuit: Action

PCM turns on MIL and disables EGR. PCM assumes throttle position switch is closed if brakes are applied or TP sensor position is less than or equal to 18 degrees. PCM assumes throttle position switch is open if brakes are not applied or TP sensor position is greater than 18 degrees.

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 remains 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.