P0751

Circuit Description

The PCM identifies a 1-2 shift solenoid valve condition by monitoring the commanded gear ratio versus the actual gear ratio. If the PCM detects a gear ratio that is outside the limits for a particular commanded gear, then DTC P0751 sets. DTC P0751 is a Type A DTC.

Conditions for Running the DTC

^ No MAF DTCs P0101, P0102 or P0103.
^ No TP DTCs P0121, P0122 or P0123.
^ No VSS DTCs P0502 or P0503.
^ No A/T Input (shaft) Speed Sensor (ISS) DTCs P0716 or P0717.
^ No 1-2 shift solenoid valve electrical DTC P0753.
^ No 2-3 shift solenoid valve electrical DTC P0758.
^ No Transmission Fluid Pressure (TFP) manual valve position switch DTC P1810.
^ No TCC PWM solenoid valve DTC P1860.
^ The engine run time is greater than 5 seconds. The engine is not in fuel cut off.
^ The TFP manual valve position switch indicates D1, D2, D3 or D4.
^ The transmission fluid temperature is greater than -18°C (0°F).
^ A shift is not in progress. The throttle angle is greater than 11 degrees.
^ The vehicle speed is greater than 6 km/h (4 mph).

Conditions for Setting the DTC

DTC P0751 sets when Case 1 and Case 4 are true, or when Case 2 and Case 3 are true.

Case 1
^ First gear is commanded.
^ The gear ratio is 1.54:1-1.71:1 for 1 second.
^ Delivered torque is greater than 82 N.m (60 lb ft).

Case 2
^ Second gear is commanded.
^ The gear ratio is 2.87:1-3.11:1 for 3 seconds.
^ Delivered torque is greater than 96 N.m (70 lb ft).

Case 3
^ Third gear is commanded.
^ The gear ratio is 0.65:1-0.71:1 for 3 seconds.
^ Delivered torque is greater than 82 N.m (60 lb ft).

Case 4
^ Fourth gear is commanded.
^ The gear ratio is 0.95:1-1.05:1 for 5 seconds.
^ Delivered torque is greater than 96 N.m (70 lb ft).

Action Taken When the DTC Sets

^ The PCM illuminates the malfunction indicator lamp (MIL).
^ SERVICE ENGINE SOON, SERVICE TRANSMISSION displays on the driver information center (DIC).
^ The PCM commands 2nd gear.
^ The PCM commands default line pressure
^ The PCM inhibits TCC engagement.
^ The PCM freezes steady state adapts
^ The PCM freezes garage shift adapts
^ The PCM stores DTC P0751 in PCM history.

Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from PCM history.
^ The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids

^ Inspect the transmission fluid for sediment.
^ Inspect the transmission filter for debris.
^ Refer to the Shift Solenoid Valve State and Gear Ratio table.
^ DTC P0751 may set approximately 10 seconds after DTC P0753 has set, follow the diagnostic table for DTC P0753 before proceeding to the diagnostic table for DTC P0751. Repairing the condition that caused DTC P0753 will likely eliminate DTC P0751.

Test Description

Important: Do not drive the vehicle for an extended period of time, because additional internal damage may occur.

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

3. This step verifies that DTC P0751 is set. Set up data pairs (current gear and gear ratio) on the scan tool. Drive the vehicle while commanding FIRST gear with the scan tool.
4. This step verifies that the gear ratio indicated a SECOND gear start, and the vehicle does not achieve FIRST gear. The list of components should be inspected and repaired if faulty.
6. This step verifies that the gear ratio indicates THIRD gear and the vehicle does not achieve FOURTH gear. The list of components should be inspected and repaired if faulty.
8. This step verifies that the gear ratio indicates FIRST gear and the vehicle does not achieve SECOND gear. The list of components should be inspected and repaired if faulty.
10. This step verifies that the gear ratio indicates FOURTH gear and the vehicle does not achieve THIRD gear. The list of components should be inspected and repaired if faulty.