DTC 21

Fig. 002 - Wiring Diagram for Code 21 Throttle Position Sensor. (Signal Voltage High):

CODE 21, TPS (SIGNAL VOLTAGE HIGH)

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about .5 volts at idle to 4.5 volts at Wide Open Throttle.
The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.
Code 21 will set if:
a. TPS signal voltage is greater than 2.5 volts for 8 seconds;
b. Engine speed less than 1200 RPM. This is the purpose for placing shift lever in drive; and
C. MAP is less than 57 kPa (8 psi) (no load condition).

Fig. 001 - Chart Code 21 Throttle Position Sensor (Signal Voltage High):

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.
3. Check for reference voltage from the ECM. To prevent damage to ECM, be sure to disconnect black connector when checking circuit wiring for open shorts to ground.