DTC 21

The Throttle Sensor (TPS) provides a voltage signal that changes relative to the throttle valve. Signal voltage will vary from less than 0.45 volts at idle to about 4.0 volts at wide open throttle (WOT).

The TPS signal is one of the most important inputs used by the ECM for fuel control and for many of the ECM controlled outputs.

Code 21 will set if:

^ TPS signal voltage is greater than 4.7 volts for 5 seconds.
^ Engine speed is less than 1,200 rpm. This is the purpose for placing shift lever in "Drive".
^ MAP is less than 50 kPa (7.5 psi) or equal to a no load condition.

1. Confirms Code 21, and that fault is present.
2. Simulates Code 22: If the ECM recognizes the low signal voltage and sets Code 22 the ECM and wiring are OK.