P0751

DTC P0751 1-2 (A) Shift Solenoid Performance [1 Of 2]:

DTC P0751 1-2 (A) Shift Solenoid Performance [2 Of 2]:

Performance Chart:

1-2 (A) Shift Solenoid:

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 four different shifting combinations.

When the Vehicle Control Module (VCM) detects incorrect Gear Ratios, then DTC P0751 sets. DTC P0751 is a type D DTC. For California emissions vehicles DTC P0751 is a type A DTC.

CONDITIONS FOR SETTING THE DTC

^ No Manifold Absolute Pressure (MAP) Sensor DTCs P0106, P0107, or P0108.
^ No Throttle Position (TP) Sensor DTCs P0121, P0122, or P0123.
^ No Vehicle Speed Sensor (VSS) DTC P0502.
^ 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 Valve Position Switch (TFP Val. Position Sw.) DTC P1810.
^ No Four Wheel Drive DTC P1875.
^ The engine must be running for 5 seconds and not in fuel cutoff.
^ The vehicle speed is greater than 4.2 km/h (2.5 mph).
^ The TP Sensor is greater than 12%.
^ The Engine Torque is 70 lb ft (88 Nm) to the following:

- 375 lb ft (470 N.m).

^ The transmission fluid temperature 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:

- When the 1-2 SS Valve is stuck OFF, first gear is commanded and the ratio is equal to second gear for greater than 2.0 seconds and 4th gear is commanded with the Torque Converter Clutch (TCC) locked and the ratio equals 3rd for greater than 3 seconds.
- When the 1-2 SS Valve is stuck ON, second gear is commanded and the ratio is equal to first ear for greater than 3 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The VCM commands maximum line pressure.
^ The VCM freezes shift adapts.
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles.

CONDITIONS FOR CLEARING THE DTC

1. For California emissions only, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
2. A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
3. The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS

^ Verify that the transmission meets the specifications in the 4L80-E shift speed chart.
^ Other internal transmission failures can cause more than one shift to occur.
^ First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic chart.

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