P0744 Fault Code in Toyota: Causes, Symptoms, and Fixes

This code indicates that the Powertrain Control Module (PCM) or Transmission Control Module (TCM) has detected an intermittent problem with the torque converter clutch solenoid circuit. The torque converter clutch is responsible for locking the torque converter to improve fuel efficiency and reduce slippage at cruising speeds.

Possible Symptoms:

1. Check Engine Light (CEL) ON
2. Transmission slipping
3. Poor fuel economy
4. Shuddering at highway speeds
5. Overheating transmission
6. Vehicle may not go into lockup mode

Common Causes:

1. Faulty TCC solenoid (intermittent operation)
2. Wiring issues – damaged, corroded, or loose connectors in the TCC circuit
3. Low or dirty transmission fluid
4. Internal transmission problems (valve body issues, worn clutches)
5. Faulty PCM/TCM (less common)

Diagnostic & Fix:

1. Check transmission fluid – level and condition. Replace if dirty or burnt.
2. Inspect wiring & connectors – especially around the transmission harness and TCC solenoid.
3. Test TCC solenoid – measure resistance, check for intermittent failure.
4. Check valve body – sticking valves can cause TCC issues.
5. Scan live data – monitor TCC command vs. actual lockup.
6. If wiring/solenoid are good, internal transmission inspection may be needed.