Auto Trans

TPS Circuit Signal Voltage High (A/T Only):

Code 21 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: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 21 will set if:

^ Engine is running.
^ TPS signal voltage greater than approximately 4.9 volts.
^ Above conditions exist for over 0.7 seconds.

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

3. Probing light GREEN/BLACK wire with a test light checks the TPS ground circuit because an open or 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 +/- 0.05 volt at wide open throttle (WOT).