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 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.

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.