Circuit Description
The Pressure Control Solenoid (PC Sol.) Valve is a PCM-controlled device that regulates the transmission line pressure. The PCM compares the TP voltage, the engine RPM, and other inputs in order to determine the appropriate line pressure for a given load. The PCM regulates the pressure by applying a varying amperage to the PC Sol. The applied amperage varies from 0.1 to 1.1 amps. The PCM monitors the applied amperage.
When the PCM detects a continuous open or a continuous short to ground in the PCS circuit, then DTC P0748 sets. DTC P0748 is a type D DTC.
Conditions for Setting the DTC
| • | The system voltage is 10-17 volts. |
| • | The PCM recognizes that the Pressure Control Solenoid Valve has reached the valve's electrical high limit. |
| • | The PCM recognizes that the Pressure Control Solenoid Valve has reached the valve's electrical low limit. |
Action Taken When the DTC Sets
| • | The PCM freezes shift adapts from being updated. |
| • | The PCM does NOT illuminate the Malfunction Indicator Lamp (MIL). |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the wiring for any poor electrical connections at the PCM. Inspect the wiring 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 an open condition, massage the wiring harness while watching the test equipment for any changes. |
Test Description
The numbers below refer to the Step numbers on the diagnostic table.
-
This step verifies that the PCM can command the PC Sol. Valve.
-
This step verifies that the PC Sol. Valve has the correct resistance. This step verifies that the Automatic Transmission wiring harness has the correct resistance.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check , Section 6 | |||||||
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. Does the PC Act. Current remain within the specified range? | PC Ref Current ±0.16 amp | Go to Diagnostic Aids | ||||||||
Is the resistance within the specified range? | 3-7ohms | |||||||||
4 |
Refer to Transmission Oil Pan Replacement, in On-Vehicle Service. Is the resistance within the specified range? | 3-7ohms | ||||||||
5 | Replace the PC Solenoid Valve. Refer to Pressure Control Solenoid Valve Replacement, in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||||
6 | Repair the open in the Automatic Transmission Wiring Harness. Refer to Electrical Diagnosis, Section 8. Is the repair complete? | -- | -- | |||||||
7 |
Refer to Electrical Diagnosis, Section 8. Did you find and correct a problem? | -- | ||||||||
8 |
Refer to Electrical Diagnosis, Section 8. Did you find and correct a problem? | -- | ||||||||
9 |
Did you find and correct a problem? | -- | ||||||||
10 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming , Section 6. Is the replacement complete? | -- | -- | |||||||
11 |
Has the test run and passed? | -- | System OK |
