With PFI

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

Wiring Diagram for Throttle Position Sensor:

CODE 21
THROTTLE POSITION SENSOR (TPS) CIRCUIT (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. A 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 CKT155.


DiagnosticAids:

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 155 is open or CKT 417 is shorted to voltage. If Code 21 is "Intermittent," refer to "DIAGNOSIS BY SYMPTOMS - NO TROUBLE CODE STORED".