P055

Circuit Description

The TP sensor on the PFI engine is 'self adjusting'. When the ignition is turned off, the PCM executes a TP sensor learning routine. After key off, the PCM will retract the ISC until the ISC throttle position switch opens and the throttle lever is resting on the minimum air screw. At that time, the PCM stores the TP sensor value and calculates a correction. If the same correction factor occurs on two consecutive key 'off' cycles, the TP sensor is then corrected to 0 degrees using the correction factor 'learned'. If the value needs correction by more than ±6.50 degrees, PCM Code P055 will be stored in memory at the next key ON cycle. Note: Parameter PD01 displays uncorrected TP sensor values.

Test Condition(s)

Test continuously.

Failure Condition(s)

'Learned' TP sensor correction 6.50 degrees or greater.

Action Taken

PCM learned TP sensor value set to 0.

Notes on Fault Tree

1. Checking for ISC/TP sensor codes which could cause Code P055.
2. Checking if the TP sensor is really out of range or if the throttle position switch is open causing it to look that way.
3. Checking TP sensor adjustment. PCM Data PDO1, TP sensor displays uncorrected TP sensor so that it can be used to check TP sensor adjustment.
4. If TP sensor is within range, ISC and throttle switch operation need to be thoroughly checked. The throttle linkage needs to be checked for proper operation check that throttle and cruise cables are not binding, proper throttle return spring operation, and that throttle shaft and blades are free to move.