P0756

Diagnostic Chart:

Performance:

Circuit Description
The 2-3 Shift Solenoid Valve (2-3 SS Valve) controls fluid flow acting on the 2-3 shift valves. The 2-3 SS Valve is a normally-open exhaust valve used with the 1-2 Shift Solenoid Valve (1-2 SS Valve) in order to allow for four different shift combinations.

If the VCM detects a non first gear ratio while first gear is commanded or a first gear ratio while fourth gear is commanded, then DTC P0756 sets. Diagnostic Trouble Code (DTC) P0756 is a type D DTC. For California emissions vehicles, DTC P0756 is a type A DTC.

Conditions for Setting the DTC

^ No TP Sensor DTCs P0121, P0122, or P0123.
^ No Output Shaft Speed (OSS) DTCs P0502.
^ No 4WD Lo DTC P1875.
^ No TFP Val. Position Sw. DTC P1810.
^ No Shift Solenoid Electrical DTCs P0753 or P0758.
^ No Automatic Transmission Input Shaft Speed (A/T ISS) Sensor DTCs P0716 or P0717.
^ The engine runs more than 475 RPM for 7 seconds and not be in fuel cut off.
^ Not in 4WD Lo.
^ The engine vacuum is 0-105 kPa.
^ The vehicle speed is greater than 6 km/h (4 mph).
^ The throttle position is greater than 12%.
^ The Transmission Fluid Temperature (TFT) is 20-130°C (68-266°F).
^ No engine torque malfunction.
^ The engine torque is 100 Nm (80 lb ft) to the following:

- 470 N.m (375 lb ft).

^ All of the above conditions are met and either of the two following conditions occur:
- When the 2-3 SS Valve is stuck on, the commanded gear equals 1st and the ratio equals 4th for greater than 2 seconds, and the commanded gear equals 2nd and the ratio equals 3rd for greater than 2 seconds. The conditions exist for 2 occurrences.
- When the 2-3 SS Valve is stuck off, the commanded gear equals 3rd and the ratio equals 2nd for greater than 4 seconds. The condition exists for 4 occurrences.

Action Taken When the DTC Sets

^ The transmission immediately lands to 2nd gear.
^ The VCM commands maximum line pressure.
^ The VCM freezes shift adapts.
^ The VCM illuminates the Malfunction Indicator Lamp (MIL) for California emissions vehicles.

Conditions for Clearing the MIL/DTC

1. For California emissions vehicles, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
2. A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
3. The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

Diagnostic Aids

^ Verify that the transmission meets the specifications in the Shift Speed table.
^ Other internal transmission failures may cause more than one shift to occur.
^ The customer may complain of an engine over-rev condition or neutral condition in 4th gear.
^ First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset.
^ Refer to Shift Solenoid Valve State and Gear Ratio 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 the function of the TFP Val. Position Sw.
3. This step tests for a selected gear ratio versus a ratio not obtainable under normal operating conditions.