P0748

Circuit Description
The PCS is a PCM Controlled device used to regulate transmission line pressure. The PCM compares TPS voltage, engine rpm, and other inputs to determine the line pressure appropriate for a given load. The PCM will regulate the pressure by applying a varying amperage to the PCS. The applied amperage can vary from 0.1 to 1 amp, and is monitored by the PCM.
This DTC detects a continuous open or short to ground in the PCS circuit or the PCS. This is a type "C" DTC.





Wiring Diagram

Part 1 Of 3:

Part 2 Of 3:

Part 3 Of 3:

Inspection Procedure



Conditions For Setting The DTC
- Battery voltage is between 10 and 16 volts.
- The PCM detects that the different between commanded and actual current is 200 milliampere (mA) for over 1 second.
- Engine speed is greater then 300 rpm.

Action Taken When the DTC Sets
- The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
- Maximum line pressure.
- The PCM will illuminate the CHECK TRANS Lamp.

Conditions For Clearing The DTC/CHECK TRANS Lamp
- The PCM will turn "off" the CHECK TRANS Lamp after three consecutive ignition cycles without a failure reported.
- The DTC can be cleared from PCM history by using a scan tool.
- The DTC will be cleared from memory when the vehicle has achieved 40 warm-up cycles without a failure reported.
- The PCM will cancel the DTC default actions when the fault no longer exists and the ignition is cycled "off" long enough to power down the PCM.

Diagnostic Aids
- Inspect the wiring for poor electrical connection at the PCM and at the transmission 5-way connector. Look for possible bent, backed out, deformed or damaged terminals Check for weak terminal tension as well. Also check for a chafed wire that could short to bare metal or other wiring. Inspect for a broken wire inside the insulation.
- When diagnosing for a possible intermittent short or open condition, move the wiring harness while observing test equipment for a change.

Test Description
The numbers refer to the step numbers on the diagnostic chart:
2. This test checks the ability of the PCM to command the PCS.
3. This test checks the PCS and internal wiring harness for incorrect resistance.