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Error Code P0742 is defined as Torque Converter Clutch Circuit Stuck On. Meaning, the torque converter clutch circuit is performing abnormally, which usually happens due to dirty transmission fluid or valves.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system or vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one make and/or model to another.
Modern vehicles with automatic transmissions (transaxles) use torque converter between the transmission and the engine to improve the torque output from the engine and drive the rear wheels.
Both the engine and the transmission are connected through a fluid coupling mechanism inside the torque converter, which is actually what multiplies the torque until speed is equal and create a ‘stall’ speed where the difference between the actual RPM of the engine and the transmission input of the RPM is about 90% efficient. The TCC (Torque Converter Clutch) solenoids, commands the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) or the TCM (Transmission Control Module) to activate and use the hydraulic fluid and engage the torque converter clutch to make a solid coupling and improve efficiency.
Error Code P0742 happens when the transmission control module detects a fault with the circuit that runs the torque converter clutch solenoid.
Note that this code is similar to P0740, P0741, P0743 and P0744.
Using advanced scan tool can give you access to other diagnostic trouble codes associated with the TCM that may be present. If there are other transmission related trouble codes other than the P0742, the problem may be an electrical failure.
As with other error codes Error Code P0742 activates the Check Engine light. Different cases and situations can have different symptoms, and symptoms can vary in their severity as well. For other vehicles, drivers may not notice any issues at all. In other cases however, it will be impossible for torque converter to disengage. Other common symptoms for this trouble code include:
- Transmission slippage
- Overheating transmission
- Difficulty when shifting
- Engine stalls or dies
Error Code P0742 can be caused by variety of things, such as:
- Low or dirty transmission fluid
- Faulty torque converter solenoid valve
- Internal mechanical problem with the transmission
How to Check
Technicians usually use OBD-II scanner to the vehicle’s onboard computer to retrieve the data bout the vehicle and come up with the proper diagnosis.
Once they have the data, they will proceed on resetting the code and take the vehicle for a test drive to see if the code comes back.
If the code does come back, that means the condition was not tripped in error and the problem is legitimate and must be fixed.
How to Fix
Repairs for this error code are as easy as its diagnosis, which includes the following:
- Check for damage or loose connections of transmission harness
- Check for resistance in torque converter clutch solenoid and internal transmission wiring
- Defective TCM that causes codes without known issues must be repaired or replaced as necessary
In some cases, torque converter clutch wiring malfunctions and other issues are overlooked. In this case, technicians instead replace the lock up solenoids or torque converters when they don’t really have to. Thus, it is really important to have a proper diagnosis.
Also, Error Code P0742 may indicate a serious problem, such as shifting issues, rough running or stalling when idling. Things can be more than just annoying, and potentially dangerous. Thus, it is crucial to get the repairs as soon as possible, whether the problem is small or large.