P0756

CIRCUIT DESCRIPTION
The 2-3 Shift Solenoid Valve (2-3 SS Valve) controls the fluid flow acting on the 2-3 shift valves. The solenoid is a normally-open exhaust valve. With the 1-2 Shift Solenoid Valve (1-2 SS Valve), the 2-3 SS Valve allows four different shifting combinations.

When the VCM detects a 1-2-2-1 only or a 4-3-3-4 only shift pattern, depending on the state of the mechanical failure, then DTC P0756 sets. DTC P0756 is a type B DTC.

CONDITIONS FOR SETTING THE DTC
^ No TP DTCs P0122 or P0123.
^ No VSS Assy. DTC P0502.
^ No Transmission Fluid Temperature (TFT) Sensor DTCs P0712 or P0713.
^ No TCC Stuck ON DTC P0742.
^ No 1-2 SS Valve DTC P0753.
^ No 2-3 SS Valve DTC P0758.
^ No TFP Va. Position Sw. DTC P1810.
^ No TCC PWM Sol. Valve DTC P1860.
^ No TCC Sol. Valve DTC P1864.
^ No 3-2 SS Valve Assy. DTC P1886.
^ The vehicle speed is greater than 24 km/h (15 mph).
^ The gear range is D4.
^ The engine speed is greater than 450 RPM for 8 seconds.
^ The transmission fluid temperature is 20-130°C (68-266°F).
^ The TCC is OFF.

All of the above conditions are met two consecutive times and either of the following two fail conditions occurs:

1. The solenoid is stuck ON and Cases 2 and 3 occur two consecutive times.
2. The solenoid is stuck OFF and Cases 1 and 3 occur two consecutive times.

Case 1
^ The TP angle is greater than 45%.
^ First gear is commanded for 2 seconds.
^ The speed ratio is 0.5-2.6 (speed ratio is the engine speed divided by the output speed).
^ The transmission output speed is 600-1500 RPM.
^ The TCC slip speed is -100 to -3000 RPM for 1 second.

Case 2
^ The TP angle is 13-50%.
^ The TP angle is within +/- 3%.
^ Third gear is commanded for 2 seconds.
^ The 3rd gear speed ratio is greater than the last 2nd gear speed ratio minus 0.25.
^ The 3rd gear TCC slip speed is greater than or equal to the last 2nd gear TCC slip speed plus 300 RPM for 2.5 seconds.
^ Discontinue the test if time since the shift commanded is 6 seconds.

Case 3
^ The TP angle is greater than 13%.
^ Fourth gear is commanded for 1 second.
^ The speed ratio is 2.05-8.
^ The transmission output speed is 1400-2500 RPM.
^ The TCC slip speed is 100-1000 RPM for 1 second.

ACTION TAKEN WHEN THE DTC SETS
^ The VCM commands maximum line pressure.
^ The VCM freezes shift adapts from being updated.
^ The VCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC
^ The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
^ 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.
^ 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 4L60-E shift speed chart.
^ Other internal transmission failures may cause more than one shift to occur.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic chart.

2. This Step verifies that the scan tool commanded all shifts, that all shift solenoids responded correctly, but all the shifts did not occur.