P088

DTC P088:

Brake Switch Circuit:

CIRCUIT DESCRIPTION:
This diagnostic test checks for the Torque Converter Clutch (TCC) always engaged by monitoring the slip. Under certain operating conditions of the transaxle, the slip must be above a certain level. If the slip is not present while the transaxle is operating under this condition then the TCC must be engaged.

TEST CONDITION(S):
1. Codes P021, P022, P028 and P056 not set.
2. Engine running.
3. Throttle position 15.7 degrees or greater.
4. Software commanding TCC disengagement.
5. In 3rd or 4th gear.

FAILURE CONDITION(S):
Slip speed between 5 and 10 rpm for 4 seconds. (Slip = engine rpm - transaxle rpm.)

ACTION TAKEN:
1. PCM turns "ON" the "SERVICE ENGINE SOON" MIL.
2. Freeze shift adapts from being updated.
3. PCM disables torque converter clutch.

NOTES ON FAULT TREE:
1. Testing torque converter clutch brake switch input to the PCM P171. If the input is working correctly, the display will change from "HI" to "LO" to "HI." If it is not working correctly, the display will not change.
2. Checking CKT 422 for a short to ground inside the transaxle.
3. Checking PCM's ability to control PCM output P002. Voltage will cycle between 0 volt and 12 volts if PCM is OK.
4. Checking CKT 422 for a short to ground between C112 and the PCM.
5. If P171 stays "HI," check for a short to voltage in the TCC control circuitry. If P171 stays "LO," check CKT 750 for an open or CKT 420 for an open or short to ground.
6. Possible hydraulic cause of getting TCC apply when not electrically commanded.