VT25-E Automatic Transmission

VT25-E AUTOMATIC TRANSMISSION

DTC P0742

Test 1-5:

Circuit Description with VT25-E Automatic Transmission
The transmission control module (TCM) controls the TCC pressure control solenoid valve pulse width modulation. When the solenoid is commanded on, it exhausts release oil and allows regulated apply oil to flow to the apply circuit of the TCC system. The pressure in this system applies the pressure plate to the converter housing, and couples the transmission and engine directly through the TCC. The TCC slip speed should be near zero when fully applied.

At start-up with the vehicle in park, the TCC slip speed is sampled. If the slip speed is less than a calibrated value a fail counter is incremented.

When the TCM detects that a certain percentage of the TCC slip speed samples have failed when the TCC is commanded OFF in park, DTC P0742 sets. DTC P0742 is a type B DTC.

Conditions for Running the DTC
^ No transmission range switch DTCs P0705, P1756, or P1758.
^ No ISS DTCs P0716 or P0717.
^ No OSS DTCs P0722, or P0723.
^ No TCC system stuck OFF DTC P0741.
^ No engine torque DTC P1779.
^ No TCC enable solenoid valve DTCs P 1888 or P1889.
^ The engine speed is 500-2000 RPM
^ The selected range is PARK.
^ The transmission fluid temperature is greater than 20°C (68°F).
^ The throttle position angle is less than 3 percent.
^ The change in throttle position angle is 2 percent or less since start-up.

Conditions for Setting the DTC
Eighty percent of the TCC slip speed samples are less than 3 RPM.

Action Taken When the DTC Sets
^ The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The TCM commands full TCC engagement when output shaft speed is above 500 RPM.
^ The TCM commands maximum pressure to the input clutch.
^ The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records.
^ The TCM stores DTC P0742 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
^ The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the MIL/DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids
The customer may notice an engine stalling condition.

Test Description
The number refers to the step number on the diagnostic table.
3. This step inspects and repairs the components that caused the DTC to set.