P0744

Symptoms

• Check Engine Light
• shudder during TCC engagement
• transmission slipping or feeling like it drops out of gear
• delayed or harsh shifts
• hesitation under acceleration
• possible engine stalling at idle
• reduced fuel economy
• possible transmission over-temperature warning.

Probable causes

• 1) Failing TCC (lock-up) solenoid — internal coil degradation
• contamination
• or unpredictable open/close behavior. 2) Damaged wiring or connectors — corroded pins
• broken wires
• loose clips interrupting the signal between solenoid and control module. 3) Low or contaminated transmission fluid
• debris obstructing fluid flow through the valve body is one of the most common triggers. 4) Faulty torque converter clutch itself. 5) TCM/driver circuit fault. Note: the most common misdiagnosis is overlooking wiring faults — solenoids and torque converters are frequently replaced in error.

Diagnostic steps

1. Scan codes and record freeze frame data.
2. Check transmission fluid level and condition; verify the correct fluid type is present, at the right level, red and odor-free — top up or service if contaminated.
3. Visually inspect the TCC solenoid harness and connectors for corrosion, frayed conductors and bent pins.
4. With a multimeter, verify continuity and measure solenoid coil resistance against the manufacturer specification.
5. With the engine at operating temperature, monitor the solenoid circuit voltage during a road test — a supply that drops or spikes indicates an intermittent circuit or driver fault.
6. Repair wiring faults before replacing parts; only replace the TCC solenoid (or torque converter) after the circuit has been verified good.
7. Clear codes and road test at steady cruise to confirm TCC engagement without shudder and that the code does not reset.