P0751
Circuit Description
The Powertrain Control Module (PCM) identifies a 1-2 Shift Solenoid Valve (1-2 SS Valve) problem by monitoring the commanded gear versus gear ratio.
If the PCM detects a gear ratio that is outside its limits for a particular commanded gear, then DTC P0751 sets. DTC P0751 is a Type B DTC.
Conditions for Setting the DTC
^ No Throttle Position (TP) DTCs P0121, P0122 or P0123 are set.
^ No Vehicle Speed (VSS) sensor DTCs P0502 or P0503 are set.
^ No Automatic Transmission Input Speed Sensor (A/T ISS) DTCs P0716 or P0717 are set.
^ No 1-2 shift solenoid valve electrical DTC P0753 is set.
^ No 2-3 shift solenoid valve electrical P0758 is set.
^ No TCC Pulse Width Modulated (PWM) Sol. DTC P1860 is set.
^ No Transmission Fluid Pressure Switch (TFP Sw.) DTC P1810 is set.
^ The engine has been running for more than 5 seconds.
^ Not in fuel shut off mode.
^ The vehicle speed is greater than 8 km/h (5 mph).
^ A shift is not in progress.
^ The throttle angle is greater than 14%.
^ The transmission fluid temperature is greater than 20°C (68°F).
^ The transmission is not in Park/Neutral.
^ The engine torque is 70-270 N.m (50-200 lb ft).
^ All of the above conditions are met and cases 1 and 4 are true for 3 seconds twice.
^ All of the above conditions are met and cases 2 and 3 are true for 3 seconds twice.
Case 1
- First gear is commanded.
- The gear ratio is 1.52:1 to 1.62:1.
Case 2
- Second gear is commanded.
- The gear ratio is 2.87:1 to 2.97:1.
Case 3
- Third gear is commanded.
- The gear ratio is 0.65:1 to 0.75:1.
Case 4
- Fourth gear is commanded.
- The gear ratio is 0.95:1 to 1.05:1.
Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) after 2 consecutive ignition cycles with a failure reported.
^ The PCM commands maximum line pressure.
^ The PCM disables shift adapts.
^ The PCM inhibits 3-2 downshifts when 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 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
^ Inspect the transmission fluid for sediment.
^ Inspect the transmission filter for debris.
^ Refer to Shift Solenoid Valve State and Gear Ratio table.
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 chart.
3. 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.