Code 21A Throttle Position (TP) Sensor Circuit

SIGNAL VOLTAGE HIGH




Circuit Description
The Throttle Position (TP) Sensor provides a voltage signal that changes relative to the Throttle Body position. Signal voltage will vary from less than 1.25 volts at idle to about 5.0 volts at Wide Open Throttle.

The TP Sensor signal is one of the most important inputs used by the Engine Control Module (ECM) for Fuel control and for many of the ECM controlled outputs.




Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This checks to see if Diagnostic Trouble Code (DTC) 21A is the result of a hard failure or an intermittent condition. A DTC 21A will set if.
- TP Sensor reading above 4.6 volts.
- Engine speed less than 1200 revolution per minute (rpm).
- Manifold Absolute Pressure reading below 50 kPa.
- All of the above conditions are present for 2.3 seconds.

2. This step simulates conditions for a DTC 21B. If the ECM recognizes the change of state, the ECM and BLU/ORG and BLU/RED are OK.
3. This step isolates a faulty Sensor, ECM, or an open BLK/WHT wire. If the BLK/WHT is open, there may also be a DTC 23A.

Diagnostic Aids
- A "Scan Tool" displays Throttle Position in volts. Closed Throttle voltage should be less than 1.25 volts. TP Sensor voltage should increase at a steady rate as Throttle is moved to Wide Open Throttle.
- A DTC 21A will result in BLK/WHT wire is open or BLU/RED is shorted to voltage. If DTC 21A is intermittent, refer to Diagnosis by Symptom. Symptom Related Diagnostic Procedures