P055

Code PO55:

PCM Circuit:

DESCRIPTION
The Throttle Position (TP) sensor on the Port Fuel Injection (PFI) engine is "self adjusting." At key "OFF" the Powertrain Control Module (PCM) executes a TP sensor learning routine. After key "OFF," the PCM will retract the Idle Speed Control (ISC) until the ISC throttle position switch opens and the throttle linkage 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 -2.9 degrees or +3.0 degrees, Code P055 will be stored in memory at the next key "ON" cycle.

NOTE: Parameter PD01 displays uncorrected TP sensor values.

TEST CONDITIONS
Test continuously.

FAILURE CONDITIONS
"Learned" TP sensor valve is less than -2.9 degrees or greater than 3.0 degrees.

ACTION TAKEN
At next key "ON," the PCM will log Code P055 as current. No messages or messages are displayed.

NOTES ON FAULT TREE
1. Checking TP sensor adjustment. PCM Data PD01, TP sensor displays uncorrected TP sensor so that it can be used to check TP sensor adjustment.

2. TPS adjustment is OK.

3. If TP sensor adjustment is OK, ISC and throttle switch operation need to be thoroughly checked. The throttle linkage needs to be checked for proper operation -- throttle, cruise and TV cables not binding, proper throttle return spring operation throttle shaft and blades free to move.

NOTES ON INTERMITTENTS
Manipulate ISC wiring while observing PCM Input PI72 and while observing ISC operation during PCM output cycling PO07. Manipulate TP sensor wiring and connector while observing PCM Data PD01, TP sensor. Check for TP sensor secured to throttle body (both TORX screws tight). Cycle the TP sensor through its full travel while observing PD01 for erratic behavior. Check for proper part number TP sensor installed on vehicle. Remove and reinstall the TP sensor, ISC and PCM connectors and ensure that they are latched.