Code P021, Shorted Throttle Position (TP) Sensor: Action

PCM turns on MIL and disables TCC. PCM sets TP sensor equal to 13 degrees when throttle position switch is open and 6 degrees when throttle position switch is closed. PCM disables 3rd and 4th gears.

1. If TP sensor or wiring is shorted, data parameter PD01 will read 87 degrees or greater.
2. Check for shorted TP sensor or wiring. If data value stays greater than -3 degrees with TP sensor and PCM. An open in circuit No. 808 will cause TP sensor signal to be always high whenever TP sensor is connected.
3. Checks for an open or short to power in circuit No. 474.

Fig 1: Code P021 Schematic, Shorted Throttle Position (TP) Sensor

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P021 Diagnostic Flow Chart, Shorted TP Sensor

Courtesy of GENERAL MOTORS CORP.