Standardized generic DTCTransmission

P0742 — Torque Converter Clutch Circuit Stuck On

P0742 is the standardized powertrain DTC for “Torque Converter Clutch Circuit Stuck On.” The code identifies the monitored condition; it does not by itself prove which part failed.

Standardized generic definition

Torque Converter Clutch Circuit Stuck On

DTC category

Transmission

Diagnostic priority

Moderate to high. A stuck-on converter clutch can stall the engine; excessive slip can overheat transmission fluid.

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What P0742 means

P0742 is the standardized powertrain DTC for “Torque Converter Clutch Circuit Stuck On.” The code identifies the monitored condition; it does not by itself prove which part failed.

Start with the stored data and the simplest external checks before replacing the component named in the code.

How to interpret the code wording

“Stuck On” means the monitored function appears active when the module expects it to be released or off. Compare command and feedback, then test the actuator/solenoid, wiring, hydraulic/pneumatic path, and mechanical sticking as applicable.

Possible symptoms

Shudder during lockup
Engine stalls when coming to a stop if clutch remains applied
Higher cruising RPM
Transmission overheating or limp mode

Causes to test

These are diagnostic possibilities, not a statistical parts-replacement ranking. Vehicle-specific service information takes priority.

Torque-converter clutch solenoid/hydraulic control problem
Valve-body wear or contamination
Low/incorrect/degraded transmission fluid
Wiring or TCM control fault
Torque converter clutch mechanical failure

Step-by-step diagnostic workflow

Check fluid level/condition using the manufacturer procedure and correct fluid specification.
Review TCC command, slip speed, gear, and fluid temperature during the event.
Inspect electrical circuits and solenoid operation before condemning the converter.
Follow transmission-specific hydraulic/pressure tests and TSBs.
Perform circuit or mechanical tests specified by service information; repair the confirmed root cause.
Clear codes only after repair, then complete an appropriate drive cycle and verify the code and symptoms do not return.

Preserve evidence: EPA OBD guidance emphasizes that stored DTCs and freeze-frame data are important to proper diagnosis. Save them before clearing codes.

Scan data worth checking

TCC command/duty
TCC slip RPM
Input and output speed
Transmission fluid temperature
Commanded gear

Severity and drivability

Moderate to high. A stuck-on converter clutch can stall the engine; excessive slip can overheat transmission fluid.

Stop driving and investigate immediately if there is a flashing MIL, oil-pressure warning, overheating, fuel leakage, severe misfire, major loss of power, abnormal mechanical noise, or a transmission that is slipping badly.

Common diagnostic mistakes

Replacing the torque converter before valve-body/solenoid diagnosis
Using the wrong transmission fluid
Driving extensively with high slip and overheated fluid

Related generic codes

P0741 — Torque Converter Clutch Circuit Performance or Stuck OffP0743 — Torque Converter Clutch Circuit ElectricalP0740 — Torque Converter Clutch Circuit/OpenP0744 — Torque Converter Clutch Circuit Intermittent

Source and accuracy notes

Generic DTC structure and standardized definitions are governed by SAE J2012/J2012DA. Actual enable criteria, thresholds, circuit pinouts, test values, software conditions, and repair procedures vary by vehicle. Use current OEM service information for the exact year/engine/calibration and check applicable manufacturer technical service bulletins. See the site methodology and primary-reference policy.