P056

DTC PO56:

PCM Circuits:

CIRCUIT DESCRIPTION
This diagnostic test checks for a transaxle input speed sensor circuit problem. If the engine is running and the vehicle is moving above 10 mph then the transaxle input speed must be non-zero. If the turbine speed is less than 50 rpm with a vehicle speed of 10 mph or greater, Code P056 will set.

TEST CONDITIONS
1. Codes P024, P075 and P091 NOT set.
2. Transaxle not in Park/Neutral.
3. Engine running.
4. Vehicle speed 10 mph or greater.

FAILURE CONDITION
Turbine speed 50 rpm or less for 2 seconds.

ACTION TAKEN
1. Powertrain Control Module (PCM) turns "ON" the Malfunction Indicator Lamp (MIL) (Service Engine Soon).
2. PCM calculates the transaxle input speed based on the output speed and the gear ratio of the gear commanded.
3. PCM calculates slip speed from the calculated input speed and engine rpm.
4. Torque Converter Clutch (TCC) engaged.
5. PCM disables torque management.
6. Transaxle shift adapts are maintained at current levels.
7. Garage shift adapts are maintained at current levels.

NOTES ON FAULT TREE
1. With engine idling in PARK or NEUTRAL PD72 should read between 50 and 100 rpm less than engine rpm.
2. The transaxle input speed sensor will generate a frequency of greater than 0 Hz when the vehicle is idling. If it does not check CKT 1230, CKT 1231 and speed sensor for open/shorts inside the transaxle.
3. Checking CKT 1230 and CKT 1231 for opens or shorts to the PCM. If wire OK, the PCM is faulty.

NOTES ON INTERMITTENTS
Manipulate CKT 1230 and CKT 1231. Look for sources of Electromagnetic Interference (EMI), such as sensor wires run along side spark plug wires or high power transmitters (like mobile radios) operating in the vicinity.