Code 21 - TPS Open Or MISADJUSTED

The Throttle Position Sensor (TPS) is a variable resistor that supplies the ECM with throttle opening information. The sensor is supplied with a 5-volt reference signal. Sensor resistance is lowest (high signal to ECM) at wide open throttle.

Code 21 means that the ECM has seen high voltage at terminal "A2" for more than 30 seconds with engine speed below 1120 RPM.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

Checks to confirm if Code is still present.
Checks reference voltage at TPS harness connector to determine whether problem is in electrical circuit or TPS.
Checks to see if low reference voltage is due to a grounded wire or ECM.

Fig 1: Flow Chart, Code 21, TPS Open Or Misadjusted

Fig 2: Flow Chart, Code 21, TPS Open Or Misadjusted