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CODE 21 THROTTLE POSITION SENSOR (TPS) CIRCUIT

Code Chart 21A:

TPS Circuit:

CIRCUIT DESCRIPTION:

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle valve position. Signal voltage will vary from less than 1.25 volts at idle to about 5.0 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 most of the ECM control outputs.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

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

Code 21 will set if:

^ Engine speed less than 1800 rpm.
^ TPS reading above 2.5 volts.
^ MAP reading below 60 kPa.
^ Above conditions exist for 2 seconds.

2. This step simulates conditions for a Code 21B. If the ECM recognizes the change, the ECM, and the PPL/RED wire and the PPL/ORN wire are OK.

3. This step isolates a faulty sensor ECM or an open BLK/WHT wire. If the BLK/WHT wire is open, there may also be a Code 23A.

DIAGNOSTIC AIDS:

A Scan tool displays throttle position in volts. Closed throttle voltage should be less than 1.25 volts. TPS voltage should increase at a steady rate as throttle is moved to WOT. A Code 21A will result if BLK/WHT wire is open or PPL/RED wire is shorted to voltage. If Code 21A is intermittent, Testing and Inspection