P0742
Torque Converter Clutch Circuit Stock OnP0742 is a generic OBD-II powertrain diagnostic trouble code: Torque Converter Clutch Circuit Stock On. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0742 means
P0742 is set when the PCM or TCM determines that the torque converter clutch (TCC) is remaining engaged—locked—when it should be releasing. The TCC is a friction clutch built into the torque converter that, once vehicle speed and throttle conditions are met, mechanically couples the engine crankshaft to the transmission input shaft, eliminating converter slip and improving fuel economy. When it cannot disengage, the converter behaves as a rigid shaft at all times, including at low speed and during stops.
The most frequent trigger is contamination in the transmission fluid causing the TCC solenoid to stick in its energised (on) position, or debris lodging in the valve body passage that controls converter clutch apply pressure. Because the solenoid operates on pressurised fluid as well as electrical signals, even good wiring will not allow the clutch to release if hydraulic flow is blocked. A fluid service and solenoid replacement resolve the majority of cases.
Mechanically, a worn or damaged torque converter itself can cause the clutch friction material to stick or weld to the converter cover, preventing release regardless of solenoid or fluid condition. This scenario is typically accompanied by a shudder during lockup events, metal particles in the fluid, and often by code P0741 (TCC performance) alongside P0742.
A driver-noticeable consequence of a stuck TCC is engine stall when decelerating to a stop, because the drivetrain cannot absorb the speed differential between the still-moving wheels and the idling engine. Rough low-speed operation and lurching on light throttle are also common complaints. Prompt repair prevents torque converter destruction and protects the transmission from overload.
Common causes
Most-frequently reported root causes when P0742 is logged.
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1
Contaminated or low transmission fluid blocking TCC solenoid
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2
Faulty or sticking TCC solenoid
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3
Stuck valve or blocked passage in the transmission valve body
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4
Worn or damaged torque converter clutch friction material
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5
Short circuit in the TCC solenoid control wiring
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6
Poor connector contact at the TCC solenoid
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7
Faulty PCM/TCM commanding full solenoid duty cycle (rare)
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8
Internal transmission mechanical failure
Symptoms drivers notice
How to diagnose P0742
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scanner, record freeze-frame data, and note all related transmission codes
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2
Inspect transmission fluid level and condition; burnt smell or dark colour indicates fluid degradation
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3
Road-test above 45 mph on a gentle incline; monitor TCC solenoid duty cycle and slip speed on live data—if duty cycle holds at 100% while slip speed stays near zero the clutch is confirmed stuck on
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4
Test TCC solenoid resistance with a multimeter and compare to manufacturer specification; check for shorts to ground
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5
Inspect solenoid wiring harness and connector for corrosion, chafing, or backed-out pins
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6
Perform a fluid and filter service; re-test to determine if the fault clears
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7
If fault persists, inspect valve body for stuck TCC apply valve or blocked hydraulic passages
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8
If converter friction material damage is suspected (metal in fluid, persistent shudder), evaluate torque converter replacement
Related powertrain codes
- P0700 — Transmission Control System Malfunction
- P0701 — Transmission Control System Range/Performance
- P0702 — Transmission Control System Electrical
- P0703 — Torque Converter/Brake Switch B Circuit Malfunction
- P0704 — Clutch Switch Input Circuit Malfunction
- P0705 — Transmission Range Sensor A Circuit malfunction (PRNDL Input)
Frequently asked questions
Why does my car stall at traffic lights when P0742 is active?
A stuck-on TCC mechanically links the engine to the drivetrain. When you slow to a stop the wheels decelerate but the engine cannot spin freely, causing it to stall—the same effect as stalling a manual-transmission car by releasing the clutch too slowly.
What is the difference between P0741 and P0742?
P0741 (TCC Performance) flags when the converter clutch slips more than expected during lockup—a 'not locking tight enough' fault. P0742 flags when the clutch will not release—a 'stuck engaged' fault. They can coexist if the clutch is both worn and mechanically seized.
Can a fluid and filter change fix P0742?
Yes, in many cases. If fresh fluid restores proper viscosity and flow through the solenoid and valve body, the clutch may begin releasing correctly. If the solenoid itself has failed or the torque converter is mechanically damaged, a fluid change will not be sufficient.
Is it safe to drive with P0742?
Not advisable. The vehicle may stall unexpectedly at stops and transmission overheating can occur rapidly. Continuing to drive risks destroying the torque converter and potentially the transmission.
Disabling P0742 in software
RaceTune can permanently disable P0742 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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