GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2005 🢒 L300/LW300 🢒 Brakes 🢒 Park Brake 🢒 DTC P0751

Object Number: 40580 Size: MF
Master Electrical Component List
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice

Circuit Description

The 1-2 shift solenoid (SS) valve is a normally-open exhaust valve that, in conjunction with the 2-3 shift solenoid (SS) valve, allows 4 different shifting combinations. The 1-2 SS valve is attached to the control valve body, within the transmission.

The transmission control module (TCM) monitors the actual gear ratio, and compares the actual gear ratio with the commanded gear ratio. DTC P0751 sets under 2 conditions:

    • A stuck OFF 1-2 SS valve
    • A stuck OFF 1-2 shift valve

When the TCM detects a 2-2-3-3 shift pattern, then DTC P0751 sets. DTC P0751 is a type B DTC.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0751 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear

Conditions for Running the DTC
    • No MAF DTCs P0101, P0102, or P0103.
    • No MAP DTCs P0107 or P0108.
    • No TP DTCs P0121, P0122, or P0123.
    • No VSS DTCs P0502 or P0503.
    • No ISS DTCs P0716 or P0717.
    • No SS electrical DTCs P1842, P1843, P1845, or P1847.
    • The engine run time is greater than 5 seconds.
    • The transmission fluid temperature (TFT) is 20-130°C (68-266°F).
    • The TP is greater than 8 percent.
    • The engine torque is greater than 30 N·m (22 lb ft).
    • The vehicle speed is greater than 8 km/h (5 mph).

Conditions for Setting the DTC

The following occurs twice during the same trip:

    • The TCM commands 1st gear and the gear ratio is 1.54:1-1.71:1, 2nd gear, for 2 seconds.
    • The TCM commands 4th gear and the gear ratio is 0.91:1-1.07:1, 3rd gear, for 5 seconds.

Action Taken When the DTC Sets
    • The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
    • The TCM commands maximum line pressure.
    • The TCM freezes transmission adaptive functions.
    • The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
    • 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 P0751 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
    • A scan tool can clear the MIL/DTC.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an 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.

Diagnostic Aids
    • If you clear DTC P0751, and then cannot set DTC P0751 again, inspect for the following conditions:
       - Fluid contamination
       - Plugged fluid circuits
       - Restricted fluid circuits
    • Refer to Shift Solenoid Valve State and Gear Ratio .

Test Description

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

  1. This step verifies a 2-2-3-3 shift pattern.

    2.

  2. This step tests for a mechanical or hydraulic condition causing the 1-2 SS valve to be stuck OFF, or the circuit to be released.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Did you perform the Transmission Fluid Checking Procedure?

--

Go to Step 3

Go to Transmission Fluid Check

3

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

    3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from both the ECM and the TCM.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Use the scan tool snapshot mode in order to record current gear and gear ratio.
  6. Drive the vehicle in D4, in order to obtain 1-2, 2-3 and 3-4 shifts with a TP greater than 8%.

Are the current gear and gear ratio within the specified values?

1st/2nd:

1.54:1-1.71:1

3rd/4th:

0.91:1-1.07:1

Go to Step 4

Go to Diagnostic Aids

4

  1. Inspect the 1-2 shift circuit for the following conditions:
    2. • 1-2 SS valve mechanically stuck OFF
    • 1-2 shift valve stuck in the released position
    • Refer to Shift Solenoid Leak Test .
    • Damaged 1-2 SS valve O-ring
  2. Repair the circuit as necessary.

Refer to 1-2 Shift Solenoid Valve Replacement .

Did you complete the repair?

--

Go to Step 5

--

5

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. • Drive the vehicle in D4.
    • Allow the transmission to shift through all the gears.
    • Monitor the current gear and gear ratios. The actual gear ratios must match the commanded gears for 1 second, for all gears.
  4. Select Specific DTC.
  5. Enter DTC P0751.

Has the test run and passed?

--

Go to Step 6

Go to Step 2

6

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 - Vehicle in Vehicle DTC Information

System OK