P0751
Electrical Diagram:
CIRCUIT DESCRIPTION
The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls the fluid flow acting on the 1-2 and 3-4 shift valves. The 1-2 SS Valve is a normally-open exhaust valve that is used with the 2-3 Shift Solenoid Valve (2-3 SS Valve), in order to allow four different shifting combinations.
When the PCM detects a 1-1-4-4 or a 2-2-3-3 shift pattern, depending on the state of the mechanical failure, then DTC P0751 sets. DTC P0751 is a type A DTC.
CONDITIONS FOR SETTING THE DTC
^ No TP Sensor DTCs P0122 or P0123.
^ No VSS Assy. DTCs P0502 or P0503.
^ No Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) DTC P0740.
^ No TCC Stuck ON DTC P0742.
^ No 1-2 SS Valve DTC P0753.
^ No 2-3 SS Valve DTC P0758.
^ No 3-2 Shift Solenoid Valve Assembly (3-2 SS Valve Assy.) DTC P0785.
^ No TFP Val. Position Sw. DTC P1810.
^ No TCC PWM Sol. Valve DTC P1 860.
^ The engine speed is greater than 450 RPM for 8 seconds.
^ Not in fuel cutoff.
^ The gear range is D4.
^ The vehicle speed is greater than 8 km/h (5 mph).
^ The transmission fluid temperature is 20-130°C (68-266°F).
^ All of the above conditions are met three times and the combination of Conditions 1, 2, 3 and 4 or Conditions 1, 2, 3 and 5 occurs three times.
Condition 1
^ The PCM commands a 1-2 shift.
^ The TP angle is 10-35%.
^ The TP angle is constant within +/- 5%.
^ The vehicle speed is 8-40 km/h (5-25 mph).
^ Within 2 seconds, the engine speed in 2nd gear is 100 RPM greater than the last speed in 1st gear.
Condition 2
^ The PCM commands a 2-3 shift.
^ The TP angle is 10-35%.
^ The TP angle is constant within +1-7%.
^ The vehicle speed is 16-64 km/h (10-40 mph).
^ Within 2 seconds, the engine speed in 3rd gear is 50 RPM less than the last speed in 2nd gear.
Condition 3
^ The PCM commands a 3-4 shift.
^ The TP angle is 8-35%.
^ The TP angle is constant within +/- 7%.
^ The vehicle speed is 32-88 km/h (20-55 mph).
^ Within 2 seconds, the engine speed in 4th gear is 20 RPM greater than the last speed in 3rd gear.
Condition 4
^ The PCM commands 4th gear.
^ The TCC is ON.
^ The TP angle is 7-35%.
^ The speed ratio is 0.8-1.2.
^ The TCC slip speed is 200-1000 RPM for 4 seconds.
Condition 5
^ The PCM commands 4th gear.
^ The TCC is ON.
^ The TP is 7-35%.
^ The speed ratio is 0.65-0.8.
^ The TCC slip speed is -20 to +40 RPM for 4 seconds.
ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).
^ The PCM commands D2 line pressure.
^ The PCM inhibits 3-2 downshifts if the vehicle speed is greater than 48 km/h (30 mph).
^ The PCM freezes shift adapts from being updated.
^ DTC P0751 stores in PCM history.
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
^ Verify that the transmission meets the specifications in the 4L60-E Shift Speed table.
^ Other internal transmission failures may cause more than one shift to occur.
^ Refer to Shift Solenoid Valve State and Gear Ratio.
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests that the scan tool commanded all shifts and all shift solenoid valves responded correctly, but all the shifts did not occur.