DTC 21

Code 21 Chart:

Throttle Position Sensor Wiring Diagram:

CIRCUIT DESCRIPTION:

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the throttle opening. Signal voltage will vary from about 0.5 volt 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: The numbers below refer to circled numbers on the diagnostic chart.

1. Code 21 will set if:

A. Engine is running
B. TPS signal voltage is greater than approximately 4.0 volts (78%)
C. A & B conditions exists for over 5 seconds, OR
D. TPS voltage is greater than 4.9 volts. With throttle closed the TPS should read less than 0.70 volt. If it doesn't, see the ADJUSTMENT PROCEDURES.

2. With the TPS disconnected, the TPS voltage should read low if the ECM and wiring are OK.

3. Probing circuit 452 with a test light checks the TPS ground circuit because of an open or a very high resistance ground circuit will cause a Code 21.

DIAGNOSTIC AIDS:

Using a DVM to measure TPS voltage, the voltage should vary between 0.54 volt +/- 0.05 volt at closed throttle, and 5.0 volts +/- .05 volt at Wide Open Throttle (WOT).