P0743

DTC P0743












Circuit Description with 4L30-E Automatic Transmission
The Torque Converter Clutch (TCC) solenoid is located in the transmission adapter case. The solenoid valve controls the engagement and disengagement of the torque converter clutch in 3rd and 4th gears. The TCC operation is dependent on transmission fluid temperature, selected shift program, and vehicle speed.
The Transmission Control Module (TCM) provides voltage to the solenoid through an internal solid-state relay. The TCM uses a second driver to control the solenoid ground circuit. The ground control driver reports feedback voltage to the TCM. When the TCM commands the TCC ON, the voltage of the control circuit should be approximately 0 volts. When the TCM commands the TCC OFF, the voltage of the circuit should be approximately the system voltage. When the TCM detects a continuous open, short to ground, or a short to power in the TCC solenoid circuit or in the TCC solenoid valve, then DTC P0743 sets. DTC P0743 is a type B DTC.

Conditions for Running the DTC
^ The TCC is commanded OFF.
^ The TCM high side driver is closed.

Conditions for Setting the DTC
^ A short to ground:
TCM detects less than 2.45 volts for 0.18 seconds on the control circuit.
^ Open circuit:
TCM detects 2.45-3.53 volts for 0.18 seconds on the control circuit.
^ Short to battery:
TCM detects more than 4.02 volts for 0.18 seconds on the control circuit.

Action Taken When the DTC Sets
^ The TCM flashes the sport mode lamp and sends a MIL request to the ECM on the second consecutive drive trip that the diagnostic runs and fails. The ECM then illuminates the MIL.
^ The ECM records the operating conditions in the Freeze Frame at the time of the MIL request from the TCM.
^ The transmission operates in the default mode (maximum line pressure, command 4th gear, inhibit TCC, freeze shift adapts).

Conditions for Clearing the MIL/DTC
^ The ECM turns off the MIL after three consecutive drive trips during which the TCM sends no MIL request.
^ A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.
^ The scan tool clears the MIL/DTC.
^ The TCM cancels the DTC default mode actions when the ignition switch is Off long enough in order to power down the TCM.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the solenoid energizes.