P021

Code PO21:

Sensor 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 1076. The TP sensor signal circuit 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, WOT, deceleration enleanment and acceleration enrichment. Code P021 sets when the PCM detects a TP sensor signal that is too high.

TEST CONDITIONS:
RPM between 0 and 6375.

FAILURE CONDITIONS:
TP sensor value 87 degrees or greater for 0.1 seconds.


ACTION TAKEN:
1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL.

2. PCM disables the Torque Converter Clutch (TCC).

3. PCM sets TP sensor equal to 13 degrees when the Throttle Position Switch is open and 6 degrees when the Throttle Position Switch is closed.

4. PCM disables third and fourth gears.

NOTES ON FAULT TREE:
1. With TP sensor or wiring shorted. PCM data parameter PD01 will read 87 or greater.

2. Checking for shorted TP sensor or shorted wiring. If the data value stays greater than 3 with the TP sensor and PCM. An open CKT 1076 will cause the TP sensor signal to always be high whenever the TP sensor is connected.