For 1990-2009 cars

## DTC P0748 Pressure Control Solenoid Circuit Electrical 2.4L

Automatic Transmission Components VIN M
Automatic Transmission Controls Schematics 2.4L
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Powertrain Control Module (PCM) uses the Pressure Control Solenoid Valve (PC Sol. Valve) in order to regulate the transmission line pressure. The PC Sol. Valve consists of an electrical connector, a coil, an armature, a regulating spring, and a poppet valve. The PC Sol. Valve is attached to the upper control body. The PCM compares TP voltage, fluid temperature, gear states, and other inputs in order to determine the line pressure appropriate for a given load. The PCM regulates the pressure by applying a varying amperage to the PC Sol. Valve. The applied amperage varies from 0.1 amps for maximum line pressure to 1.1 amps for minimum line pressure. The PCM then monitors the amperage at the return line.

When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit, or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.

### Conditions for Setting the DTC

• | The system voltage is 9-16 volts.

• | The PC Sol. Valve duty cycle is 0% or greater than 95%.

### Action Taken When the DTC Sets

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

• | The PCM commands maximum line pressure (0 amps).

• | The PCM freezes shift adapts from being updated.

• | DTC P0748 is stored in the PCM history.

### 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 at the PCM, the transmission 20-way connector and the PC Sol. Valve 2-way connector 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

- | Corrosion

• | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

• | Extended engine cranking with a weak battery could set DTC P0748.

### Test Description

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

1. This step verifies the ability of the PCM to command the PC Sol. Valve.

2. This step verifies that the automatic transmission wiring harness and the PC Sol. Valve have correct resistance.

3. This step tests circuit 1229 of the automatic transmission wiring harness for a short to ground.

4. This step tests circuit 1228 from the engine 20-way connector to the PC Sol. Valve for a short to ground.

5. This step tests circuit 1229 from the engine 20-way connector to the PCM for an open.

6. This step tests circuit 1229 from the engine 20-way connector to the PCM for a short to ground.

7. This step tests circuit 1228 from the engine 20-way connector to the PCM for a short to ground.

#### DTC P0748 Pressure Control Solenoid Valve Circuit -- Electrical (2.4L)

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to 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 DTCs.
4. Start the engine.
5. Using the scan tool, apply 0.1 amps through 1.0 amps.
6. Observe the scan tool display.

Does the PC Act. Current amp reading differ from the desired PC Ref. Current amp reading by no more than the specified amount?

0.16 amps

Go to Diagnostic Aids

Go to Step 3

3 |

1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector (additional DTCs will set).
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 Digital Multimeter (DMM) from terminal C to terminal D and measure the resistance.

Is the resistance within the specified range?

3-7 ohms

Go to Step 7

Go to Step 4

4 | Is the resistance greater than the specified value? | 7 ohms | Go to Step 5 | Go to Step 6
5 |

1. Inspect circuit 1228 from the transmission 20-way connector to the PC Sol. Valve for an open.
2. Inspect circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for an open.

Refer to General Electrical Diagnosis .

Did you find the condition?

--

Go to Step 18

Go to Step 9

6 | Inspect circuit 1228 and circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for being shorted together. Refer to General Electrical Diagnosis . Did you find the condition? | -- | Go to Step 18 | Go to Step 9
7 | Measure the resistance from terminal D to a good ground. Is the resistance less than the specified value? | 1,000 ohms | Go to Step 8 | Go to Step 10
8 |

1. Inspect circuit 1228 from the transmission 20-way connector to the PC Sol. Valve for a short to ground.
2. Inspect circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for a short to ground.

Refer to General Electrical Diagnosis .

Did you find the condition?

--

Go to Step 18

Go to Step 19

9 | Replace the PC Sol. Valve. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the replacement complete? | -- | Go to Step 20 | --
10 |

1. Disconnect the J 39775 Jumper Harness from the transmission 20-way connector.
2. Install the J 39775 Jumper Harness to the engine side of the 20-way connector.
3. Disconnect the C2 (Black) PCM connector (additional DTCs will set).
4. Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal D of the Jumper Harness to a good ground and measure the resistance.

Is the resistance less than the specified value?

10 ohms

Go to Step 11

Go to Step 12

11 | Inspect circuit 1229 from the engine 20-way connector to the PCM connector for a short to ground. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
12 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal D of the jumper harness to the PCM terminal C2-9 and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13
13 | Inspect circuit 1229 from the engine 20-way connector to the PCM connector for an open. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
14 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal C of the jumper harness to a good ground and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16
15 | Inspect circuit 1228 from the engine 20-way connector to the PCM connector for a short to ground. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
16 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal C of the jumper harness to the PCM terminal C2-6 and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 19 | Go to Step 17
17 | Inspect circuit 1228 from the engine 20-way connector to the PCM connector for an open. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
18 | Replace the automatic transmission wiring harness. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the replacement complete? | -- | Go to Step 20 | --
19 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | Go to Step 20 | --
20 | In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info.
3. Turn the ignition switch to the RUN position.
4. Select Specific DTC. Enter DTC P0748.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1

## DTC P0748 Pressure Control Solenoid Circuit Electrical 3.1L

Automatic Transmission Components VIN M
Automatic Transmission Controls Schematics 3.1L
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Powertrain Control Module (PCM) uses the Pressure Control Solenoid Valve (PC Sol. Valve) in order to regulate the transmission line pressure. The PC Sol. Valve consists of an electrical connector, a coil, an armature, a regulating spring, and a poppet valve. The PC Sol. Valve is attached to the upper control body. The PCM compares TP voltage, fluid temperature, gear states, and other inputs in order to determine the line pressure appropriate for a given load. The PCM regulates the pressure by applying a varying amperage to the PC Sol. Valve. The applied amperage varies from 0.1 amps for maximum line pressure to 1.1 amps for minimum line pressure. The PCM then monitors the amperage at the return line.

When the PCM detects a continuous open or short to ground in the PC Sol. Valve circuit, or the PC Sol. Valve, then DTC P0748 sets. DTC P0748 is a type D DTC.

### Conditions for Setting the DTC

• | The system voltage is 9-16 volts.

• | The PC Sol. Valve duty cycle is 0% or greater than 95%.

### Action Taken When the DTC Sets

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

• | The PCM commands maximum line pressure (0 amps).

• | The PCM freezes shift adapts from being updated.

• | DTC P0748 is stored in the PCM history.

### 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 at the PCM, the transmission 20-way connector and the PC Sol. Valve 2-way connector 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

- | Corrosion

• | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

• | Extended engine cranking with a weak battery could set DTC P0748.

### Test Description

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

1. This step verifies the ability of the PCM to command the PC Sol. Valve.

2. This step verifies that the automatic transmission wiring harness and the PC Sol. Valve have correct resistance.

3. This step tests circuit 1229 of the automatic transmission wiring harness for a short to ground.

4. This step tests circuit 1228 from the engine 20-way connector to the PC Sol. Valve for a short to ground.

5. This step tests circuit 1229 from the engine 20-way connector to the PCM for an open.

6. This step tests circuit 1229 from the engine 20-way connector to the PCM for a short to ground.

7. This step tests circuit 1228 from the engine 20-way connector to the PCM for a short to ground.

#### DTC P0748 Pressure Control Solenoid Circuit -- Electrical (3.1L)

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to 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 DTCs.
4. Start the engine.
5. Using the scan tool, apply 0.1 amps through 1.0 amps.
6. Observe the scan tool display.

Does the PC Act. Current amp reading differ from the desired PC Ref. Current amp reading by no more than the specified amount?

0.16 amps

Go to Diagnostic Aids

Go to Step 3

3 |

1. Turn the ignition OFF.
2. Disconnect the transmission 20-way connector (additional DTCs will set).
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 Digital Multimeter (DMM) from terminal C to terminal D and measure the resistance.

Is the resistance within the specified range?

3-7 ohms

Go to Step 7

Go to Step 4

4 | Is the resistance greater than the specified value? | 7 ohms | Go to Step 5 | Go to Step 6
5 |

1. Inspect circuit 1228 from the transmission 20-way connector to the PC Sol. Valve for an open.
2. Inspect circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for an open.

Refer to General Electrical Diagnosis .

Did you find the condition?

--

Go to Step 18

Go to Step 9

6 | Inspect circuit 1228 and circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for being shorted together. Refer to General Electrical Diagnosis . Did you find the condition? | -- | Go to Step 18 | Go to Step 9
7 | Measure the resistance from terminal D to a good ground. Is the resistance less than the specified value? | 1,000 ohms | Go to Step 8 | Go to Step 10
8 |

1. Inspect circuit 1228 from the transmission 20-way connector to the PC Sol. Valve for a short to ground.
2. Inspect circuit 1229 from the transmission 20-way connector to the PC Sol. Valve for a short to ground.

Refer to General Electrical Diagnosis .

Did you find the condition?

--

Go to Step 18

Go to Step 9

9 | Replace the PC Sol. Valve. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the replacement complete? | -- | Go to Step 20 | --
10 |

1. Disconnect the J 39775 Jumper Harness from the transmission 20-way connector.
2. Install the J 39775 Jumper Harness to the engine side of the 20-way connector.
3. Disconnect the C2 (Clear) PCM connector (additional DTCs will set).
4. Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 Digital Multimeter (DMM) from terminal D of the Jumper Harness to a good ground and measure the resistance.

Is the resistance less than the specified value?

10 ohms

Go to Step 11

Go to Step 12

11 | Inspect circuit 1229 from the engine 20-way connector to the PCM connector for a short to ground. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
12 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal D of the jumper harness to the PCM terminal C2-46 and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13
13 | Inspect circuit 1229 from the engine 20-way connector to the PCM connector for an open. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
14 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal C of the jumper harness to a good ground and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16
15 | Inspect circuit 1228 from the engine 20-way connector to the PCM connector for a short to ground. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
16 | Using the J 35616-A Connector Test Adapter Kit, connect the J 39200 DMM from terminal C of the jumper harness to the PCM terminal C2-45 and measure the resistance. Is the resistance less than the specified value? | 10 ohms | Go to Step 19 | Go to Step 17
17 | Inspect circuit 1228 from the engine 20-way connector to the PCM connector for an open. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | Go to Step 20 | --
18 | Replace the automatic transmission wiring harness. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the replacement complete? | -- | Go to Step 20 | --
19 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | Go to Step 20 | --
20 | In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info.
3. Turn the ignition switch to the RUN position.
4. Select Specific DTC. Enter DTC P0748.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1