Circuit Description
The Pressure Control Solenoid Valve (PC Sol. Valve) regulates actuator feed fluid passing through the solenoid into torque signal pressure. The Powertrain Control Module (PCM) uses a pulse width modulated signal in order to control the torque signal pressure. The PCM compares various inputs in order to determine the appropriate pressure for a given load. The PCM varies the current to the PC Sol. Valve from 0.1-1.1 amp. An internal current monitor within the PCM provides feedback in order to determine actual PC Sol. Valve current draw.
When the PCM detects a commanded current draw that differs from the actual current draw by more than a calibrated value, then DTC P0748 sets. DTC P0748 is a Type C DTC.
Conditions for Setting the DTC
| • | No Incorrect Gear Ratio DTC P0730. |
| • | No Maximum Adapt and Long Shift DTC P1811. |
| • | The system voltage is 10-17 volts. |
| • | The engine run time is greater than 1 second. |
| • | The difference between the commanded PC Sol. Valve current and the actual PC Sol. Valve current is 0.05 amps or more for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | SERVICE VEHICLE SOON displays on the Driver Information Center (DIC). |
| • | The PCM commands maximum line pressure. |
| • | The PCM disables steady state adapts. |
| • | The PCM disables upshift adapts. |
| • | The PCM disables garage shift adapts. |
| • | DTC P0748 is stored in the PCM history. |
Conditions for Clearing the MIL/DTC
| • | The commanded PC Sol. Valve current and the actual PC Sol. Valve current are within 0.05 amps of each other for 2 seconds. |
| • | 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 poor electrical connections at the PCM, the transmission 20-way connector, the PC Sol. Valve connector and all other circuit connecting points 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 |
| - | Moisture intrusion |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the PCM responds to scan tool commands, and that the DTC could set intermittently.
-
This step verifies that the resistance value is within specifications. Use the J 35616-A Connector Test Adapter Kit, in order to avoid damaging the terminals.
-
This step confirms a resistance value above the high parameter.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |||||
Important: Before clearing the DTC(s), use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM. Does the actual PC Sol. Valve reading differ from the commanded PC Sol. Valve reading by no more than the specified amount? | 0.05 amp | Go to Diagnostic Aids | ||||||
Does the DMM display a PC Sol. Valve resistance within the specified range? | 3-8 ohms | |||||||
Is the resistance greater than the specified value? | 8 ohms | |||||||
5 |
Refer to Electrical Diagnosis, Section 8. Did you find the condition? | -- | ||||||
6 | Inspect circuits 1228 and 1229 of the Automatic Transmission Wiring Harness for a short together. Refer to Electrical Diagnosis, Section 8. Did you find the condition? | -- | ||||||
7 | Measure the resistance from terminal D to the transmission case. Is the resistance less than the specified value? | 10 ohms | ||||||
8 |
Refer to Electrical Diagnosis, Section 8. Did you find the condition? | -- | ||||||
9 | Replace the Automatic Transmission Wiring Harness. Refer to Automatic Transmission Wiring Harness Replacement in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||
10 | Replace the Pressure Control Solenoid Valve. Refer to Pressure Control Solenoid Valve Replacement in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||
11 |
Is the resistance greater than the specified value? | 10 ohms | ||||||
12 |
Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | ||||||
13 |
Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | ||||||
14 | Replace the PCM. Refer to PCM Replacement/Programming , Section 6. Is the replacement complete? | -- | -- | |||||
15 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
