P0743 indicates an electrical fault in the torque converter clutch (TCC) solenoid circuit. The powertrain control module detects an open, short, or unexpected resistance in the circuit that controls the lock‑up clutch inside the torque converter.
The solenoid coil may be open or shorted, preventing proper electrical operation.
Corroded, broken, or chafed wires and poor connector contacts in the TCC circuit are common.
Insufficient fluid level or degraded fluid can affect solenoid operation and cause electrical anomalies.
A stuck valve or debris in the valve body can create abnormal solenoid current draw.
Internal driver failure in the PCM is rare but possible after all other causes are eliminated.
Almost never. The PCM is the last item to consider; the fault is almost always the solenoid, wiring, or fluid condition.
Short trips are possible, but the torque converter will not lock up, causing higher fuel consumption, overheating risk, and potential transmission damage over time.
If the code was triggered by low or contaminated fluid, correcting the fluid may allow the code to clear after a drive cycle, but the underlying electrical fault must still be verified.
On many vehicles the solenoid is accessible by removing the transmission pan and valve body; on others the transmission must be removed. Consult the service information for the specific application.