E021

Diagnostic Chart.:

Sensor Wiring Diagram:

DESCRIPTION:

The Throttle Position Sensor (TPS) is a three wire sensor or potentiometer with a five volt reference input from CKT 474, and ground from CKT 1076. The TPS signal circuit (CKT 417) varies between ground and 5 volts based on the position of the throttle plates. At low throttle angle, the TPS signal voltage is low. The 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 .7 seconds.

ACTION TAKEN:

1. ECM turns on "SERVICE ENGINE SOON" telltale.
2. ECM disables the viscous converter clutch.
3. ECM uses 13 degrees for TPS value with ISC throttle switch open and 6 degrees for TPS value when ISC throttle switch closes.
4. Fourth gear disabled.

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 1076 between the TPS and ECM. An open in CKT 1076 will result in high TPS values whenever the TPS is plugged in.

NOTE ON INTERMITTENTS:

If code E021 is stored as history, 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.