P0751
DTC P0751 (4.2L)
Circuit Description
The 1-2 shift solenoid (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 SS valve, in order to allow 4 different shifting combinations.
If the powertrain control module (PCM) detects a 2-2-3-3 shift pattern, then DTC P0751 sets. DTC P0751 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0751 1-2 Shift Solenoid Valve Performance - No First or Fourth Gear
Conditions for Running the DTC
- No VSS DTCs P0502 or P0503.
- No TCC stuck ON DTC P0742.
- No 1-2 SS valve DTC P0753.
- No 2-3 SS valve DTC P0758.
- No TP sensor DTCs P1120 or P1220.
- The engine speed is greater than 450 RPM for 5 seconds.
- The engine is not in fuel cutoff.
- The gear range is D4.
- The TP angle is 10 percent or greater.
- The transmission fluid temperature is 20-130° C (68-266° F).
- The system voltage is 10-18 volts.
- The engine torque is 68-542 N.m (50-400 lb ft).
- The transmission output speed is 150 RPM or greater.
- The transfer case ratio in 4WD Low is 0.9 to 1.2.
- The transfer case ratio in 4WD High is 2.6 to 2.85.
Conditions for Setting the DTC
DTC P0751 sets if both of the following conditions occur twice:
Condition 1
- The PCM commands first gear for 2 seconds.
- The estimated gear ratio is 1.2-1.8.
- The torque converter efficiency is greater than or equal to 0.35.
- All conditions are met for 0.5 seconds.
Condition 2
- The PCM commands fourth gear for 1 second.
- The estimated gear ratio is 0.95-1.15.
- All conditions are met for 6 seconds.
Action Taken When the DTC Sets
- The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
- The PCM commands D2 line pressure.
- The PCM commands TCC OFF.
- The PCM inhibits fourth gear in hot mode.
- The PCM freezes transmission adaptive functions.
- The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
- 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 can clear the MIL/DTC.
- 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/or the ignition switch is OFF long enough in order to power down the PCM.
Diagnostic Aids
- Verify that the transmission meets the specifications in the table Shift Speed.
- Refer to the table 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 PCM commanded all shifts, that all shift solenoid valves responded correctly, but that all the shifts did not occur.
