For 1990-2009 cars

## DTC P0748 2.2L (L61)

Master Electrical Component List
Automatic Transmission Controls Schematics 2.2L
OBD II Symbol Description Notice

### Circuit Description

The PCM uses the pressure control (PC) solenoid valve in order to regulate the transmission line pressure. The PC solenoid valve consists of an electrical connector, a coil, an armature, a regulating spring, and a poppet valve. The PC solenoid valve is attached to the control valve 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 solenoid 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, short to ground or short to voltage in the PC solenoid valve circuit, then DTC P0748 sets. DTC P0748 is a type C DTC.

### Conditions for Running the DTC

The engine is running.

### Conditions for Setting the DTC

The PC solenoid valve duty cycle is 0 percent or greater than 95 percent.

### Action Taken When the DTC Sets

• | The PCM does not illuminate the malfunction indicator lamp (MIL).

• | The PCM illuminates the service vehicle soon (SVS) lamp.

• | The PCM commands maximum line pressure, 0 amps.

• | The PCM freezes transmission adaptive functions.

• | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Failure Records.

• | The PCM stores DTC P0748 in PCM history.

### Conditions for Clearing the SVS Lamp/DTC

• | The PCM turns OFF the SVS lamp when the condition no longer exists.

• | A scan tool can clear the SVS Lamp/DTC.

• | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.

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

### 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 solenoid valve.

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

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 2.2L (L61)
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.

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 PCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Start the engine.
6. Using the scan tool, apply 0.1 amps through 1.0 amps.
7. Observe the scan tool display.

Does the PC Sol. Actual Current differ from the PC Sol. Ref. Current by more than the specified amount?

0.16 amps

Go to Step 3

Go to Intermittent Conditions in Engine Controls - 2.2L (L61)

3 |

1. Turn OFF the ignition .
2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
3. Install the J 44152 jumper harness (20 pins) on the transmission side of the AT inline 20-way connector.
4. Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminals C and D of the J 44152 .

Refer to Automatic Transmission Inline 20-Way Connector End View

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. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.
2. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.

Refer to Testing for Continuity in Wiring Systems.

Did you find a condition?

--

Go to Step 19

Go to Step 20

6 | Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for being shorted together between the AT inline 20-way connector and the PC solenoid valve. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | -- | Go to Step 19 | Go to Step 20
7 | Measure the resistance from terminal C of the J 44152 to ground. Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance less than the specified value? | 1,000 ohms | Go to Step 8 | Go to Step 9
8 |

1. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground between the AT inline 20-way connector and the PC solenoid valve.
2. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground between the AT inline 20-way connector and the PC solenoid valve.

Refer to Testing for Short to Ground in Wiring Systems.

Did you find a condition?

--

Go to Step 19

Go to Step 20

9 | Measure the resistance between terminal C and all other terminals, except terminal D, of the J 44152 . Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance between terminal C and any other terminal, except terminal D, less than the specified value? | 10 ohms | Go to Step 19 | Go to Step 10
10 |

1. Disconnect the J 44152 from the transmission side of the AT inline 20-way connector.
2. Install the J 44152 on the engine side of the AT inline 20-way connector.
3. Disconnect PCM connector C2. Additional DTCs may set.
4. Using the DMM and the J-35616 connector test adapter kit, measure the resistance from terminal D of the J 44152 to ground.

Refer to Automatic Transmission Inline 20-Way Connector End View

Is the resistance less than the specified value?

10 ohms

Go to Step 11

Go to Step 12

11 | Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
12 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminal D of theJ 44152 and terminal 9 of the PCM connector C2. Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13
13 | Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
14 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance from terminal C of the J 44152 to a good ground. Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16
15 | Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
16 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminal C of theJ 44152 and terminal 6 of the PCM connector C2. Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance less than the specified value? | 10 ohms | Go to Step 17 | Go to Step 18
17 | Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 21
18 | Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
19 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Replacement. Did you complete the replacement? | -- | Go to Step 22 | --
20 | Replace the PC solenoid valve. Refer to Pressure Control Solenoid Valve Replacement Did you complete the replacement? | -- | Go to Step 22 | --
21 | Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.0L (L81). 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. Turn ON the ignition, with the engine OFF.
4. Select Specific DTC.
5. Enter DTC P0748.

Has the test run and passed?

--

Go to Step 23

Go to Step 2

23 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 2.2L (L61) | System OK

## DTC P0748 3.0L (L81)

Master Electrical Component List
Automatic Transmission Controls Schematics 3.0L
OBD II Symbol Description Notice

### Circuit Description

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

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

### Conditions for Running the DTC

The engine is running.

### Conditions for Setting the DTC

The PC solenoid valve duty cycle is 0 percent or greater than 95 percent.

### Action Taken When the DTC Sets

• | The TCM does not request the ECM to illuminate the malfunction indicator lamp (MIL).

• | The TCM requests the ECM to illuminate the service vehicle soon (SVS) lamp.

• | The TCM commands maximum line pressure, 0 amps.

• | The TCM freezes transmission adaptive functions.

• | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.

• | The TCM stores DTC P0748 in TCM history.

### Conditions for Clearing the SVS Lamp/DTC

• | The TCM clears the SVS lamp request when the condition no longer exists.

• | A scan tool can clear the SVS Lamp/DTC.

• | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.

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

### Test Description

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

1. This step verifies the ability of the TCM to command the PC solenoid valve.

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

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81)
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.

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 TCM.

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Start the engine.
6. Using the scan tool, apply 0.1 amps through 1.0 amps.
7. Observe the scan tool display.

Does the PC Sol. Actual Current differ from the PC Sol. Ref. Current by more than the specified amount?

0.16 amps

Go to Step 3

Go to Intermittent Conditions in Engine Controls - 3.0L (L81)

3 |

1. Turn OFF the ignition .
2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
3. Install the J 44152 jumper harness (20 pins) on the transmission side of the AT inline 20-way connector.
4. Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminals C and D of the J 44152 .

Refer to Automatic Transmission Inline 20-Way Connector End View .

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. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.
2. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the AT inline 20-way connector and the PC solenoid valve.

Refer to Testing for Continuity in Wiring Systems.

Did you find a condition?

--

Go to Step 19

Go to Step 20

6 | Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for being shorted together between the AT inline 20-way connector and the PC solenoid valve. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | -- | Go to Step 19 | Go to Step 20
7 | Measure the resistance from terminal C of the J 44152 to ground. Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance less than the specified value? | 1,000 ohms | Go to Step 8 | Go to Step 9
8 |

1. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground between the AT inline 20-way connector and the PC solenoid valve.
2. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground between the AT inline 20-way connector and the PC solenoid valve.

Refer to Testing for Short to Ground in Wiring Systems.

Did you find a condition?

--

Go to Step 19

Go to Step 20

9 | Measure the resistance between terminal C and all other terminals, except terminal D, of the J 44152 . Refer to Automatic Transmission Inline 20-Way Connector End View Is the resistance between terminal C and any other terminal, except terminal D, less than the specified value? | 10 ohms | Go to Step 19 | Go to Step 10
10 |

1. Disconnect the J 44152 from the transmission side of the AT inline 20-way connector.
2. Install the J 44152 on the engine side of the AT inline 20-way connector.
3. Disconnect TCM connectors C1 and C2. Additional DTCs may set.
4. Using the DMM and the J-35616 connector test adapter kit, measure the resistance from terminal D of the J 44152 to ground.

Refer to Automatic Transmission Inline 20-Way Connector End View

Is the resistance less than the specified value?

10 ohms

Go to Step 11

Go to Step 12

11 | Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground between the TCM connector C1 and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
12 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminal D of theJ 44152 and terminal 9 of the TCM connector C2. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13
13 | Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the TCM connector C1 and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
14 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance from terminal C of the J 44152 to a good ground. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16
15 | Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground between the TCM connector C1 and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
16 | Using the DMM and the J-35616 connector test adapter kit, measure the resistance between terminal C of theJ 44152 and terminal 6 of the TCM connector C1. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 17 | Go to Step 18
17 | Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 21
18 | Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the TCM connector C1 and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 22 | --
19 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Replacement. Did you complete the replacement? | -- | Go to Step 22 | --
20 | Replace the PC solenoid valve. Refer to Pressure Control Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 22 | --
21 | Replace the TCM. Refer to Transmission Control Module Replacement . 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. Turn ON the ignition, with the engine OFF.
4. Select Specific DTC.
5. Enter DTC P0748.

Has the test run and passed?

--

Go to Step 23

Go to Step 2

23 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81) | System OK