P021

Circuit Description

The Throttle Position (TP) sensor is a potentiometer. A 5 volt reference is provided on CKT 474 and ground is provided on CKT 476. The TP sensor signal CKT 417 varies between ground and 5 volts based on the position of the throttle plates. At low throttle angle, the TP sensor signal voltage is low. The PCM uses TP sensor information to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. Code P021 sets when the PCM detects a TP sensor signal that is too high.

Test Condition(s)

RPM between 25 and 3000.

Failure Condition(s)

TP sensor value 85 degrees or greater for 0.1 second.

Action Taken

1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL.
2. PCM disables the Torque Converter Clutch.
3. PCM disables transaxle Pressure Control.
4. PCM sets TP sensor equal to 13 degrees when the throttle position switch is open and to 6 degrees when the throttle position switch is closed.
5. PCM freezes transaxle in current gear.

Notes on Fault Tree

1. With TP sensor or wiring shorted, PCM data parameter PD01 will read 85 or greater.
2. Checking for shorted TP sensor or shorted wiring. If the data value stays greater than -7 with the TP sensor disconnected, the problem is in the wiring.
3. Checking for an open in CKT 476 between the TP sensor and PCM. An open in CKT 476 will cause the TP signal to always be high whenever the TP sensor is connected.