Torque Converter Clutch Stuck On
Diagnostic trouble code P0742 indicates that the Powertrain Control Module (PCM) has detected the Torque Converter Clutch (TCC) is engaged when it should be disengaged. The computer sets this code when it sees zero or near-zero slip between the engine speed and transmission input speed during conditions where the clutch should be released.
This code is considered high severity because a stuck torque converter clutch will often cause the engine to stall when stopping, creating a safety hazard in traffic. It can also lead to severe internal transmission damage if driven extensively.
Common symptoms
- Engine stalls when coming to a complete stop
- Check Engine Light is illuminated
- Harsh or delayed transmission shifting
- Vehicle shudders or shakes at low speeds
- Decreased fuel economy and potential transmission overheating
Likely causes
- Dirty, degraded, or contaminated transmission fluid
- Faulty Torque Converter Clutch (TCC) solenoid valve
- Blocked hydraulic fluid passages inside the transmission
- Damaged or shorted wiring harness to the TCC solenoid
- Internal mechanical failure of the torque converter
- Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM)
What to check before replacing parts
Check the transmission fluid level and condition.
Look for: Look for fluid that is low, heavily discolored, smells burnt, or contains excessive metal debris, which indicates internal wear or contamination causing the valve to stick.
Inspect the wiring harness and connectors leading to the transmission.
Look for: Look for frayed wires, melted insulation, or corroded connector pins that could cause a short circuit, keeping the TCC solenoid energized.
Use a scan tool to monitor TCC slip speed and command the solenoid.
Look for: Observe if the TCC slip speed remains at zero when commanded off, and listen or feel for the solenoid clicking when manually toggled via the scanner.
Test the TCC solenoid resistance using a digital multimeter.
Look for: Compare the measured ohms to the manufacturer's specification; an out-of-range reading or a short to ground indicates a failed solenoid.
Perform a transmission hydraulic pressure test.
Look for: Check if the line pressure to the torque converter clutch circuit remains high when the PCM commands the clutch to release, indicating a stuck valve or blocked passage.
This page explains the generic P0742 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.