P0751

Diagnostic Chart:

Circuit Description

The Powertrain Control Module (PCM) monitors the commanded gear and the speed ratio in order to identify a 1-2 Shift Solenoid Valve (1-2 SS Valve) problem.

When the PCM detects a 2-3 only or a 1-4 only shift pattern, then DTC P0751 sets. DTC P0751 is a type A DTC.

Conditions for Setting the DTC

^ No Throttle Position (TP) DTCs P0122 or P0123

^ No Vehicle Speed Sensor (VSS) DTCs P0502 or P0503

^ No TCC stuck ON DTC P0742

^ No 1-2 solenoid electrical DTC P0753

^ No 2-3 solenoid electrical DTC P0758

^ No TCC Pulse Width Modulation (PWM) solenoid electrical DTC P1860

^ No TCC enable solenoid electrical DTC P0740

^ The engine speed is greater than 500 RPM for 5 seconds.

^ Not in fuel shut off

^ The vehicle speed is greater than 8 km/h (5 mph).

^ The transmission temperature is 20-130°C (68-266°F).

^ The transmission range switch indicates D4.

^ The traction control is not active.

All of the above must occur and either fail cases 1, 2, 3, and 4 or 1, 2, 3, and 5 are true three times.

Failure Criteria

Case 1

^ 1-2 shift is commanded

^ The throttle position is 18-55% and is constant within 3%.

^ The vehicle speed is 8-64 km/h (5-40 mph).

^ 2nd gear is commanded and the engine speed is 100 RPM greater than the engine speed of the commanded 1st gear, within 2.0 seconds.

Case 2

^ 2-3 shift is commanded

^ The throttle position is 10-55% and is constant within 10%.

^ The vehicle speed is 32-89 Km/h (20-55 mph).

^ When 3rd gear is commanded and within 2.5 seconds, the engine speed is 130 RPM less than the engine speed of the commanded 2nd gear.

Case 3

^ 3-4 shift is commanded

^ The throttle position is 5-40% and is constant within 7%.

^ The vehicle speed is 56-121 km/h (35-75 mph).

^ When 4th gear is commanded and within 1.0 second, the engine speed is 1 RPM greater than the engine speed of the commanded 3rd gear.

Case 4

^ Fourth gear is commanded and the TCC is ON.

^ The throttle position is 7-30%.

^ The speed ratio is 0.97-1.12

^ The TCC slip is 500-1000 RPM for more than 3 seconds.

Case 5

^ Fourth gear is commanded and the TCC is ON.

^ The throttle position is 2-30%.

^ The speed ratio is 0.65-0.76

^ The TCC slip is -20 to +25 RPM for more than 3.0 seconds.

Action Taken When the DTC Sets

^ The PCM inhibits downshifts to 2nd gear if the vehicle speed is greater than 48 km/h (30 mph).

^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/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

^ Check for PRNDL DTC P0705. A PRNDL DTC affects transmission operation. A PRNDL DTC may set DTC P0751 falsely.

^ Inspect the transmission fluid for sediment.

^ Inspect the transmission filter for debris.

^ Ensure that the scan tool commanded gear has correct solenoid states and ratio.

Test Description

The number below refers to the step numbers on the diagnostic table.

3. Once the DTC is verified, replace the 1-2 shift solenoid.