P0751

Diagnostic Chart:

Diagnostic Chart (cont'd):

Performance:

Circuit Description
The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls the fluid flow action on the 1-2 and the 3-4 shift valves. The 1-2 SS Valve is a normally-open exhaust valve that is used with the 2-3 shift solenoid Valve (2-3 SS Valve) to allow tour different shifting combinations. When the PCM detects an incorrect Gear Ratio, then DTC P0751 sets. DTC P0751 is a type A DTC.

Conditions for Setting the DTC

^ No MAP Sensor DTCs P0105, P0107, or P0108.
^ No Accelerator Pedal Position (APP) Sensor DTCs P0121, P0122, P0123, P0220, P0221, P0222, P0223, P0225, P0226, P0227 or P0228.
^ No Output Speed (OSS) DTCs P0722 or P0723.
^ No Input Speed (ISS) Sensor DTCs P0716 or P0717.
^ No 1-2 SS Valve DTC P0753.
^ No 2-3 SS Valve DTC P0758.
^ No Transmission Fluid Pressure (TFP) Val. Position Sw. DTC P1810.
^ No Four Wheel Drive DTC P1875.
^ The engine must be running.
^ The vehicle speed is greater than 4.2 km/h (2.5 mph).
^ The APP Sensor is greater than 12%.
^ The Engine Torque is 75-565 Nm (50-450 lb ft).
^ No engine torque malfunctions.
^ The transmission fluid is greater than 20°C (68°F).
^ The engine speed is less than 3650 RPM.
^ Do not put in to Four Wheel Drive Low.
^ All the above conditions are met and one of the following conditions are met:

Stuck Off: (after two occurrences)
- First gear is commanded and the ratio is equal to second gear for greater than 1.7 seconds.
- Fourth gear is commanded (with TCC locked) and the ratio equals third gear for greater than 3 seconds.

Stuck On: (after five occurrences)
- Second gear is commanded and the ratio equals first gear for greater than 2.5 seconds.
- Condition is met with 5 occurrences.

Action Taken When the DTC Sets

^ The PCM commands maximum line pressure.
^ The PCM freezes shift adapts.
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the DTC

^ The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
^ 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

^ Verify that the transmission meets the specifications in the 4L80-E shift speed table.
^ Other internal transmission failures can cause more than one shift to occur.
^ First diagnose and clear any engine DTCs or APP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.Refer to Shift Solenoid Valve State and Gear Ratio table.

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

2. This step tests the function of the TFP Val. Position Sw.
3. This step tests whether the scan tool commanded all the shifts, or whether all the shift solenoids responded correctly but all the shifts did not occur.