With PFI

Code 21 - Throttle Position Sensor (TPS):

Wiring Diagram for Throttle Position Sensor (TPS):

CODE 21 - THROTTLE POSITION SENSOR CIRCUIT (TPS) SIGNAL VOLTAGE HIGH

Circuit Description:


The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle valve, Signal voltage will vary from less than 1.0 volt, at idle, to about 4.6 volts at wide open throttle (WOT).

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


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. This step checks to see if Code 21 is the result of a hard failure or an intermittent condition.

Code 21 will set if:

^ TPS reading above 2.5 volts

^ Manifold Absolute Pressure (MAP) reading below 70 kPa

^ Engine speed less than 1300 rpm

^ All of the above conditions present for 5 seconds

2. This step simulates conditions for a Code 22. If the ECM recognizes the change of state, the ECM and CKTs 416 and 417 are OK.

3. This step isolates a faulty sensor, ECM or an open CKT 452.


Diagnostic Aids:


A "Scan" tool displays throttle position in volts. Closed throttle voltage should be less than 1.0 volt. TPS voltage should increase at a steady rate as throttle is moved to WOT.

A Code 21 will result if CKT 452 is open or CKT 417 is shorted to voltage. If Code 21 is intermittent, refer to Diagnosis By Symptoms - No Trouble Codes Stored.