P0743

Circuit Description
The Torque Converter Clutch (TCC) Solenoid engages the lock-up clutch. The Powertrain Control Module (PCM) outputs system voltage in order to turn ON (energize) or remove voltage in order to turn OFF (to de-energize the TCC solenoid). The TCC solenoid controls the hydraulic pressure to the lock-up valve within the transmission. The TCC solenoid remains OFF in the 1st and 2nd gears. The TCC remains ON in the 3rd and 4th gears when the PCM deems appropriate.

The TCC solenoid is never ON during 4L operation or when the Engine Coolant Temperature is below 30°C (80°F).

Conditions for Setting the DTC
^ The voltage detected at PCM connector C3 terminal 16 is 2.0V or lower when the PCM commands the TCC control solenoid ON.
^ The voltage detected at PCM connector C3 terminal 16 is 5.5V or higher when the PCM commands the TCC control solenoid OFF.
^ Two driving cycle detection logic

Action Taken When the DTC Sets
^ DTC P0743 stores.
^ The PCM enters the fail-sate mode.
^ The Malfunction Indicator Lamp (MIL) turns ON. The Torque Converter Clutch does not engage during fail-safe mode operation.

Diagnostic Aids
Inspect for the following conditions:
^ An open or shorted TCC solenoid
^ Faulty electrical circuits (open or short to ground) between the TCC solenoid and the PCM
^ A faulty PCM

The following conditions may cause an intermittent:
^ A reduced connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation

Inspect the PCM harness connectors for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Reduced terminal-to-wire connections

If DTC P0743 cannot duplicate, the information included in the Freeze Frame data may be useful in determining the vehicle operating conditions when the DTC
set.

DTC Confirmation Procedure
1. Turn the ignition switch to the LOCK position.
2. Connect the scan tool to the data link connector (DLC).
3. Turn the ignition switch ON.
4. Use the scan tool in order to clear the following items:
^ DTC P0743
^ Any pending DTCs
5. Start the engine.
6. Warm the engine up to normal operating temperature.
7. Shift the manual selector to DRIVE range. Remain in DRIVE range for 10 seconds.
8. Accelerate the vehicle in DRIVE range. Continue driving for 20 seconds at 80 km/h (50 mph).
9. Stop the vehicle.
10. Use the scan tool in order to test for a pending DTC.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. The scan tool creates an electronic copy of the data taken when the fault occurred. The information then stores in the scan tool for later reference.
3. This step tests for proper shift points and proper TCC engagement.
5. This step tests the total resistance of the TCC solenoid circuit.
6. This step tests for a short to ground in the GRN/YEL wire.Refer to the above figure.
7. This step tests for an open in the GRN/YEL wire. Refer to the above figure.
8. This step inspects the transmission internal electrical harness for damage.