GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Vibe - AWD 🢒 Transmission/Transaxle 🢒 Automatic Transmission - MU5 🢒 DTC P0751

Circuit Description

The Powertrain Control Module (PCM) uses signals from the Vehicle Speed Sensor (VSS) and the Crankshaft Position (CKP) sensor to detect the actual gear position. The PCM then compares the actual gear with the shift schedule in the PCM memory to detect mechanical trouble of the shift solenoid #1.

Conditions for Setting the DTC

DTC P0751 will set when the following conditions are met:

    • The gear required by the PCM does not match the actual gear.
    • Two driving cycle detection logic.

Action Taken When the DTC Sets

A DTC P0751 is stored and the Malfunction Indicator Lamp (MIL) is turned ON.

Diagnostic Aids

Inspect for the following conditions:

    • Shift select cable out of adjustment.
    • Clogged or leaky shift solenoid #1.
    • Transaxle mechanical malfunction.
    • Valve body fluid passage clogged.
    • A faulty PCM

An intermittent may be caused by the following conditions:

    • A poor connection
    • Rubbed through wire insulation
    • A broken wire inside the insulation

Perform the following steps if DTC P0751 cannot be duplicated:

  1. Read the information in the freeze frame data.
  2. Use the data to determine the vehicle operating conditions when the DTC was set.

DTC Confirmation Procedure
  1. Turn the ignition switch to LOCK.
  2. Connect the Scan Tool to Data Link Connector (DLC).
  3. Turn the ignition switch to ON.
  4. Use a Scan Tool to clear the following items from the PCM memory:
    5. • The DTC
    • The pending DTC
    • Freeze frame data
  5. Start the engine and warm up to normal operating temperature.
  6. Accelerate the vehicle in Drive (D) range and test for upshifting from 1st, to 2nd, to 3rd, and 4th gears as vehicle speed increases.
  7. Stop the vehicle.
  8. Use the Scan Tool to inspect for DTC P0751.

Test Description

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

  1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

  2. This step checks for proper shift points.

    3.

  3. This step checks for a leaky shift solenoid #1.

    4.

  4. This step checks for a stuck closed shift solenoid #1.

    5.

  5. This step checks the condition of the valve body assembly.

    6.

  6. This step checks for a faulty PCM.

DTC P0751

Step

Action

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Was the On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Diagnostic System Check - Engine Controls in Engine Controls

2
  1. Install a scan tool.
  2. Turn the ignition to ON, leaving the engine OFF.
  3. Perform the scan tool Clear DTC Information function.
  4. Operate the vehicle within the Freeze Frame conditions as observed.

Does the scan tool display any other DTCs in addition to DTC P0751?

Go to applicable DTC table

Go to Step 3

3

Perform the Upshifts and Torque Converter Clutch Apply Procedure in Road Test in order to diagnose mechanical condition of transaxle.

Is the action complete?

Go to Step 4

--

4

Perform the DTC Confirmation Procedure.

Did this DTC reset?

Go to Step 5

Go to Step 11

5

  1. Remove shift solenoid #1.
  2. Apply 490 kPa (71 psi) of compressed air into shift solenoid #1 inlet port.

Did shift solenoid #1 outlet port open and air escape?

Go to Step 6

Go to Step 12

6

  1. Apply 12V to shift solenoid #1 - positive to wire, negative to case.
  2. Apply 490 kPa (71 psi) of compressed air into shift solenoid inlet.

Did shift solenoid #1 outlet port open and air escape?

Go to Step 7

Go to Step 12

7

Refer to DTC P1780 for diagnosis of PNP switch.

Is the action complete?

Go to Step 8

--

8

Remove valve body and inspect the passages for any obstructions/restrictions. Refer to Solenoids and Wiring Harness Replacement .

Is the valve body in good condition?

Go to Step 9

Go to Step 10

9

  1. Install a good PCM. Refer to Powertrain Control Module Replacement in Engine Controls.
  2. Perform the DTC Confirmation Procedure.

Does this DTC reset?

Go to Step 13

Go to Step 14

10

Repair or overhaul the valve body assembly. Refer to Solenoids and Wiring Harness Replacement .

Is the action complete?

Go to Step 15

Go to Step 14

11

A malfunction is not present at this time. Refer to Diagnostic Aids.

Is action complete?

System OK

--

12

Replace shift solenoid #1.

Is action complete?

Go to Step 15

--

13

Refer to Line Pressure Check for further diagnosis of the transaxle's performance. Repair as necessary.

Is the action complete?

Go to Step 15

--

14

Replace Powertrain Control Module (PCM). Refer to Powertrain Control Module Replacement in Engine Controls.

Is action complete?

Go to Step 15

--

15

Perform the DTC Confirmation Procedure.

Are any DTCs displayed on the Scan Tool?

Go to applicable DTC table

System OK