E021

Code E21:

Sensor Circuit:

DESCRIPTION:

The Throttle Position Sensor (TPS) is a three wire sensor or potentiometer with a five volt reference input from the PCM/ECM to the sensor CKT 474, a reference ground from the PCM/ECM to the sensor CKT 476 and an output signal (CKT 417) from the sensor to the PCM/ECM. The output signal is a DC voltage that varies with throttle angle. At low throttle angle, the TPS signal voltage is low (about .5 volts at minimum air setting) and at high throttle angles, the TPS signal voltage is high (about 4.5 volts at wide open throttle). The PCM/ECM uses TPS information to determine idle, WOT, deceleration enleanment and acceleration enrichment.

TEST CONDITIONS:

Engine speed between 25 and 3000 RPM.

FAILURE CONDITIONS:

TPS value greater than or equal to 72 degrees for 0.7 seconds.

ACTION TAKEN:

1. PCM/ECM turns on "SERVICE ENGINE SOON" telltale.
2. PCM/ECM disables the viscous converter clutch.
3. PCM/ECM sets TPS equal to 13 degrees when the throttle switch is open, and 6 degrees when the throttle switch is closed.

NOTES ON FAULT TREE:

1. Checking for shorted TPS or shorted wiring. If the data value stays greater than -7 with the TPS disconnected, the problem is in the wiring.

2. Checking for an open in CKT 476 between the TPS and the PCM/ECM. An open in CKT 476 will cause the TPS signal to always be high whenever the TPS is plugged in.

NOTE ON INTERMITTENTS:

If code E21 is intermittent, manipulate related wiring while observing PCM/ECM parameter P.O.1. Check the TPS connector for shorts to voltage. Cycle the TPS through its travel and tap on the TPS with a pencil or pocket screwdriver to test for an intermittent TPS. If the fault is induced, the parameter will skip to a high throttle angle. If wiring and connectors check out OK, substitute a known good TPS sensor and retest.