For 1990-2009 cars
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

### Circuit Description

The Pressure Control (PC) Solenoid is inside of the transmission adapter case. The PC solenoid valve is an electronic device that regulates transmission line pressure based on the current flow through its coil winding. The magnetic field produced by the coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve. The transmission control module (TCM) controls the PC solenoid valve by applying a varying amount of amperage to the solenoid.

The PC Solenoid is supplied power via the Transmission Power Relay (internal to the TCM). The TCM controls the solenoid by grounding the control circuit via an internal solid state device called a driver. The applied amperage can vary from 0.1 to 1.1 amps. Low amperage (0.1 amp) indicates high line pressure. High amperage (1.1 amps) indicates low line pressure. The duty cycle of the PC solenoid valve is expressed as a percentage of energized ON time. Zero percent indicates zero ON time (non-energized) or no current flow. Approximately 60 percent at idle indicates maximum ON time (energized) or high current flow. The TCM determines the appropriate line pressure for a given load by comparing the throttle position (TP) voltage, the engine speed and other inputs from the engine control module (ECM).

When the TCM detects a continuous open, short to power or a short to ground in the PC solenoid valve circuit or the PC solenoid valve, then DTC P0748 sets. DTC P0748 is a type B DTC.

### Conditions For Running The DTC

• | The ignition switch is in the RUN position.

• | High side driver is closed.

• | TCM is commanding PC solenoid current.

### Conditions for Setting the DTC

The TCM detects any one of the two conditions for 0.54 seconds.

• | Open or short to ground (feedback voltage is low).

• | Short to power (feedback voltage remains high).

### Action Taken When the DTC Sets

• | The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.

• | The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.

• | The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

### Conditions For Clearing the MIL/DTC

• | The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.

• | A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.

• | The scan tool clears the MIL/DTC.

• | The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

### Diagnostic Aids

Use the J 35616 connector test adapter kit for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:

• | Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

| Refer to General Electrical Diagnosis in Wiring Systems for proper procedure.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault.

### Test Description

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

1. This step will determine if the adapter case connector is disconnected or possibly loose.

2. Listen for an audible click when the solenoid operates. Ground the circuit repeatedly if necessary.

3. If the PC solenoid valve checks out OK and no condition is found with the connections at the TCM, check the wiring and connections closely. If no condition is found, the TCM may be the cause of the condition.

#### DTC P0748 PC Solenoid Circuit- Electrical

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check ? | -- | 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 DTC, use the Scan Tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the ECM/TCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Turn the ignition switch to the OFF position.
6. Disconnect the TCM connector.
7. Disconnect the 4-way transmission adapter case connector.
8. Using the J 39200 digital multimeter (DMM) and the J 35616 connector test adapter kit, measure the resistance between terminal 52 of the TCM connector and terminal B of the 4-way transmission adapter case connector.

Is the resistance lower than the specified value?

1.5 ohms

Go to Step 3

Go to Step 8

3 | Measure the resistance from terminal 52 of the TCM connector to ground. Is the resistance greater than the specified value? | 250K ohms | Go to Step 4 | Go to Step 9
4 | Measure for the presence of voltage at terminal 52 of the TCM connector. Is voltage measured? | -- | Go to Step 10 | Go to Step 5
5 | Measure the resistance between terminal 5 of the TCM connector and terminal C of the 4-way transmission adapter case connector. Is the resistance lower than the specified value? | 1.5 ohms | Go to Step 6 | Go to Step 11
6 | Measure the resistance from terminal 5 of the TCM connector to ground. Is the resistance greater than the specified value? | 250K ohms | Go to Step 7 | Go to Step 12
7 | Measure for the presence of voltage at terminal 5 of the TCM connector. Is voltage measured? | -- | Go to Step 13 | Go to Step 14
8 |

1. Inspect circuit FY740 (BLK/PPL) for an open condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find an open?

--

Go to Step 22

Go to Diagnostic Aids

9 |

1. Inspect circuit FY740 (BLK/PPL) for a short to ground condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find a short to ground condition?

--

Go to Step 22

Go to Diagnostic Aids

10 |

1. Inspect circuit FY740 (BLK/PPL) for a short to voltage condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find a short to voltage condition?

--

Go to Step 22

Go to Diagnostic Aids

11 |

1. Inspect circuit RA741 (GRY/RED) for an open condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find an open condition?

--

Go to Step 22

Go to Diagnostic Aids

12 |

1. Inspect circuit RA741 (GRY/RED) for a short to ground condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find a short to ground condition?

--

Go to Step 22

Go to Diagnostic Aids

13 |

1. Inspect circuit RA741 (GRY/RED) for a short to voltage condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find a short to voltage condition?

--

Go to Step 22

Go to Diagnostic Aids

14 | Measure the resistance between terminal B and terminal C at the transmission side of the 4-way transmission adapter case connector. Is the resistance within the specified range? | 3.5-5.5 ohms | Go to Step 17 | Go to Step 15
15 | Is the resistance greater than the specified value? | 5.5 ohms | Go to Step 18 | Go to Step 16
16 | Is the resistance less than the specified value? | 3.5 ohms | Go to Step 19 | --
17 | Measure the resistance between terminal B to ground. Is the resistance greater than the specified value? | 250K ohms | Go to Diagnostic Aids | Go to Step 19
18 |

1. Inspect circuit FY740 (BLUE) and circuit RA741 (BROWN) of the internal transmission wiring harness for an open condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find an open condition?

--

Go to Step 20

Go to Step 21

19 |

1. Inspect circuit FY740 (BLUE) and circuit RA741 (BROWN) of the internal transmission wiring harness for a shorted condition.

Refer to General Electrical Diagnosis in Wiring Systems.

2. Repair the circuit if necessary.

Refer to Wiring Repairs in Wiring Systems.

Did you find a shorted condition?

--

Go to Step 20

Go to Step 21

20 | Replace the internal transmission wiring harness Refer to Control Valve Body . Did you complete the replacement? | -- | Go to Step 22 | --
21 | Replace the pressure control solenoid valve. Refer to Converter Clutch Solenoid . Did you complete the replacement? | -- | Go to Step 22 | --
22 | Perform the following procedure in order to verify the repair.

1. Select DTC.
2. Select Clear Info.
3. Start the engine.

Is DTC P0748 set?

--

Go to Step 1

System OK