DTC P0748 Pressure Control Solenoid Circuit Electrical 5.7L and 7.4L Gas
Circuit Description
The PC Sol. Valve is a VCM-controlled device that regulates the transmission line pressure. The VCM compares TP Sensor voltage, engine RPM, and other inputs in order to determine the appropriate line pressure for a given load. The VCM regulates the pressure by applying a varying amperage to the PC Sol. Valve. The applied amperage varies from 0.1-1.1 amps. The VCM monitors the return amperage.
When the VCM detects a continuous open or short to ground in the PC Sol. Valve circuit or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.
Conditions for Setting the DTC
| • | No system voltage DTC P0560. |
| • | The engine must be running for at least 5 seconds and not in fuel cut off. |
| • | The difference in the commanded and the measured return amperage is greater than 0.16 amps. |
| • | All conditions met for 200 milliseconds (0.2 seconds). |
Action Taken When the DTC Sets
| • | The VCM disables the PC Sol. Valve, defaulting the transmission to maximum line pressure. |
| • | The VCM freezes shift adapts. |
Conditions for Clearing the DTC
- A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| • | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change. |
| • | First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
| • | Inspect for improperly wired after-market equipment. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the ability of the VCM to command the PC Sol. Valve.
-
This step tests the PC Sol. Valve and the internal wiring harness for incorrect resistance.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data. Is the PC Act. Current reading always within the specified value? | 0.16 | Go to Diagnostic Aids | ||
Automatic Transmission Connector End View Is the resistance within the specified value? | 3-7ohms | |||
4 |
Refer to Transmission Oil Pan Removal, in On-Vehicle Service. Is the resistance with the specified range? | 3-7ohms | ||
5 | Replace the PC Sol. Valve. Refer to Pressure Control Solenoid Valve Replacement, in On-Vehicle Service. Is the replacement complete? | -- | -- | |
6 | Repair the open in the internal wiring harness. Refer to Electrical Diagnosis, Section 8. Is the repair complete? | -- | -- | |
7 |
Refer to Electrical Diagnosis, Section 8. Did you find a problem? | -- | ||
8 |
Refer to Electrical Diagnosis, Section 8. Did you find a problem? | -- | ||
9 | Replace the VCM. Refer to VCM Replacement/Programming , Section 6. Is the replacement complete? | -- | -- | |
10 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
