DTC P0748 Pressure Control Solenoid Circuit Electrical. Cadillac Concours 1997

For 1990-2009 cars
Handling ESD Sensitive Parts Notice
Automatic Transmission Components
Brake Switch, Solenoids, and VSS
Brake Switch, Solenoids, and VSS
OBD II Symbol Description Notice

### 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.

If 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 has been running for more 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.

### Action Taken When the DTC Sets

• | The PCM does not illuminate the Malfunction Indicator Lamp (MIL).

• | SERVICE VEHICLE SOON, SERVICE TRANSMISSION 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.

• | The PCM inhibits torque management.

• | 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. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Inspect the wiring for poor electrical connections at the PC Sol. Valve connector. Look for the following problems:

- | 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.

1. This step verifies that the PCM responds to scan tool commands, and that the DTC could set intermittently.

2. This step verifies that the resistance value is within specifications. Use the J 35616-A Test Connector Adapter Kit, in order to avoid damaging the terminals.

#### DTC P0748 Pressure Control Solenoid Valve Circuit Electrical

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check

2

1. Install the Scan Tool ®.
2. With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, 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.

3. Record the DTC Failure Records, then clear the DTC.
4. Start the engine.
5. Enter Special Functions, PC sol. valve on the scan tool.
6. Apply several settings from 0.1 amp through 1.1 amp and observe the scan tool display.

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 Step 3

Go to Diagnostic Aids

3

1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector.
3. Install the J 39775 Jumper Harness to the transmission side of the 20-way connector.
4. Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal C to terminal D, and measure the resistance.

Is the PC Sol. Valve resistance within the specified range?

3-8 ohms

Go to Step 7

Go to Step 4

4 | Is the resistance greater than the specified value? | 8 ohms | Go to Step 5 | Go to Step 6

5

1. Inspect circuit 1228 of the Automatic Transmission Wiring Harness for an open.
2. Inspect circuit 1229 for an open.

Refer to Electrical Diagnosis, Section 8.

Did you find the condition?

--

Go to Step 9

Go to Step 10

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? | -- | Go to Step 9 | Go to Step 10
7 | Measure the resistance from terminal D to the transmission case. Is the resistance less than the specified value? | 10 ohms | Go to Step 8 | Go to Step 11

8

1. Inspect circuit 1228 of the Automatic Transmission Wiring Harness for a short to ground.
2. Inspect circuit 1229 for a short to ground.

Refer to Electrical Diagnosis, Section 8.

Did you find the condition?

--

Go to Step 9

Go to Step 10

9 | Replace the Automatic Transmission Wiring Harness. Refer to Automatic Transmission Wiring Harness Replacement, in On-Vehicle Service. Is the replacement complete? | -- | Go to Step 15 | --
10 | Replace the Pressure Control Solenoid Valve. Refer to Pressure Control Solenoid Valve Replacement, in On-Vehicle Service. Is the replacement complete? | -- | Go to Step 15 | --

11

1. Disconnect the J 39775 Jumper Harness from the transmission side of the 20-way connector.
2. Reconnect the transmission 20-way connector.
3. Disconnect PCM connector C1.
4. Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal 38 of the PCM Connector to a known good ground, and measure the resistance.

Is the resistance greater than the specified value?

10 ohms

Go to Step 12

Go to Step 13

12

1. Inspect circuit 1228 of the Engine Wiring Harness for an open.
2. Inspect circuit 1229 for an open.

Refer to Electrical Diagnosis, Section 8.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

13

1. Inspect circuit 1228 of the Engine Wiring Harness for a short to ground.
2. Inspect circuit 1229 for a short to ground.

Refer to Electrical Diagnosis, Section 8.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

14 | Replace the PCM. Refer to PCM Replacement/Programming Section 6. Is the replacement complete? | -- | Go to Step 15 | --

15

In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info.
3. Operate the vehicle under the following conditions:

3.1. | Start the engine.

3.2. | Allow the engine to run for 30 seconds.

4. Select Specific DTC. Enter DTC P0748.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1