P0751

Diagnostic Chart:

Circuit Description

The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls transmission fluid pressure on the 1-2 Shift Valve. Circuits 439/839 provide ignition voltage to the solenoid. When the Powertrain Control Module (PCM) commands the solenoid OFF, filtered line pressure is exhausted at the solenoid. When the PCM commands the solenoid ON, the Output Driver Module (ODM), within the PCM, provides a ground which energizes the solenoid. This causes the shift valve to move, closing the exhaust port and allowing line pressure to the hydraulic passage.

The PCM monitors the commanded gear and the speed ratio in order to identify a malfunction in the 1-2 Shift Solenoid Valve.

When the PCM detects a 2-2-3-3 or a 1-1-4-4 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) DTC(s) P0502 or P0503.

^ No Torque Converter Clutch (TCC) enable solenoid electrical DTC P0740.

^ No Torque Converter Clutch (TCC) stuck ON DTC P0742.

^ No 1-2 Shift Solenoid electrical DTC P0753.

^ No 2-3 Shift Solenoid electrical DTC P0758.

^ No TCC PWM Solenoid electrical DTC P1860.

^ 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 3 times.

Case 1

^ 1-2 shift is commanded.

^ The throttle position is 18-60% and is constant within 3%.

^ The vehicle speed is 864 km/h (5-40 mph).

^ 2nd gear is commanded and, within 2.0 seconds, the engine speed is 130 RPM greater than the last engine speed of the commanded 1st gear.

Case 2

^ 2-3 shift is commanded.

^ The throttle position is 10 - 60% and is constant within 10%.

^ The vehicle speed is 40 - 89 km/h (25 - 55 mph).

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

Case 3

^ 3-4 shift is commanded.

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

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

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

Case 4

^ Fourth gear is commanded and the TCC is ON.

^ The throttle position is 2-30%.

^ The speed ratio is 0.865-1.0.

^ 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 0.58-0.68.

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

Action Taken When the DTC Sets

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

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

Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL after three consecutive trips 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.

^ 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. Refer to Shift Solenoid Valve State and Gear Ratio table.

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.