E021

ECM Code E021:

DFI Sensor Circuit:

DESCRIPTION:

The Throttle Position Sensor (TPS) is a three wire sensor or potentiometer with a five volt reference input from the ECM to the sensor CKT 474, a reference ground from the ECM to the sensor CKT 476 and an output signal (CKT 417) from the sensor to the 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). Code E021 is set when the ECM sees a high throttle angle (high TPS voltage) at low engine speed. The code is designed to detect a TPS signal (CKT 417) shorted to voltage.

TEST CONDITIONS:

Engine speed between 25 and 1000 RPM.

FAILURE CONDITIONS:

TPS value greater than or equal to 80 degrees for 3 seconds.

ACTION TAKEN:

1. ECM turns on "SERVICE ENGINE SOON" telltale.
2. ECM commands BCM to display "SERVICE SOON" message on CCDIC.
3. ECM uses 12 degrees for TPS value with ISC throttle switch open and 6 degrees for TPS value when ISC throttle switch closes.
4. ECM uses engine speed for all ISC control calculations (the ECM won't use TPS reading for coast down throttle control).

NOTES ON FAULT TREE:

1. To determine location of short to voltage -- TPS or CKT 417.

2. Checking for an open ground on CKT 474. A ground open will result in high TPS values whenever the TPS is plugged in.

NOTE ON INTERMITTENTS:

If code E021 is intermittent, manipulate related wiring while observing ECM parameter EDO1. 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.
Review the snapshot data parameters stored with this code to verify failure condition. If the failure condition is verified, check and repair intermittent wiring connection, or sensor.