DTC P0748 Pressure Control Solenoid Circuit Electrical. Cadillac Concours 1996

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 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 System Voltage Malfunction DTC P0560 is set.

• | No Incorrect Gear Ratio DTC P0730 is set.

• | No Maximum Adapt. and Long Shift DTC P1811 is set.

• | 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 for 2 seconds.

### Action Taken When the DTC Sets

• | 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.

### 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.

### 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 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.

### Test Description

The numbers below refer to the step numbers on the diagnostic chart.

1. This Step ensures that you perform the Powertrain On-Board Diagnostic System check.

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

3. 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.

4. This Step confirms a resistance value above the high parameter.

5. This Step inspects circuit 1228 and circuit 1229 in the transmission for an open. You must replace the transmission harness, if you find an open in the harness.

6. This Step confirms a resistance value below the low parameter.

7. This Step inspects circuit 1228 and circuit 1229 in the transmission for a short together. You must replace the transmission harness, if you find a short together in the harness.

8. This Step confirms a resistance value below 10 ohms.

9. This Step inspects circuit 1228 and circuit 1229 in the transmission for a short to ground. You must replace the transmission harness, if you find a short to ground in the harness.

10. This Step replaces the Pressure Control Solenoid Valve after you have made all circuit inspections.

11. This Step confirms a resistance value below 10 ohms. Use the J 35616-A Test Connector Adapter Kit, in order to avoid damaging the terminals.

12. This Step inspects circuit 1228 and circuit 1229 of the Engine Wiring Harness for an open.

13. This Step inspects circuit 1228 and circuit 1229 of the Engine Wiring Harness for short to ground.

14. This Step replaces the PCM after you have inspected all components and circuitry.

#### DTC P0748 Pressure Control Solenoid 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 (tech 1) .
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. The Clear Info function will erase the data.

3. Record the DTC Failure Records.
4. Start the engine.
5. Enter A/T outputs PC sol 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. reading differ from the commanded PC Sol. 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 Jumper Harness J 39775 to the Automatic Transmission Wiring Harness 20-way connector.
4. Connect an ohmmeter from terminal C to terminal D.

Does the ohmmeter display a PC Sol. Valve resistance within the specified range?

3-8ohms

Go to Step 8

Go to Step 4

4 | Is the resistance greater than the specified value? | 8ohms | Go to Step 5 | Go to Step 6
5 | Inspect circuit 1228 and circuit 1229 of the Automatic Transmission Wiring Harness for an open. Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10
6 | Is the resistance less than the specified value? | 3ohms | Go to Step 7 | --
7 | Inspect circuit 1228 and circuit 1229 of the Automatic Transmission Wiring Harness for being shorted together. Refer to Electrical Diagnosis, Section 8. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10
8 | Connect an ohmmeter from terminal D to the transmission case. Is the resistance less than the specified value? | 10ohms | Go to Step 9 | Go to Step 11
9 | Inspect circuit 1228 and circuit 1229 of the A/T Wiring Harness 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 10
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 Jumper Harness J 39775 from the Automatic Transmission Wiring Harness connector.
2. Reconnect the transmission 20-way connector.
3. Disconnect PCM connector C1.
4. Connect an ohmmeter from terminal 38 of the Engine Wiring Harness to a known good ground.

Does the ohmmeter display a resistance greater than the specified value?

10ohms

Go to Step 12

Go to Step 13

12 | Inspect circuit 1228 and circuit 1229 of the Engine Wiring Harness 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 | Inspect circuit 1228 and circuit 1229 of the Engine Wiring Harness 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