P0742 OBD Error Code: Problem & Solutions

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When the P0742 code is stored in your vehicle it simply means that there is discrepancy in the amount of torque converter lock up needed and the amount that is detected. The TCM or transmission control module will detect this slippage on the torque converter clutch, it does this when the converter communed is off. At times, it will require several failed cycles before the check engine light is illuminated after the error code is set.

In response to the signals sent from the vehicle speed and the Engine Control Module (ECM) received by the Transmission Control Module or TCM, the Torque converter clutch or TCC solenoid valve is activated (with the gear in D4). When this happens the lock-up piston operation will then be controlled. Upon activation of the torque converter clutch solenoid valve, the torque convertor lockup clutch starts to engage creating a 1:1 RPM ratio between the rotational speed of the torque converter and the transmission input shaft. If the A/T fluid temperature is too low, the lock-up operation will be prohibited. The engine speed will change abruptly when the accelerator pedal is depressed less than 2/8 in the lock-up condition. If at all there’s a huge jump in engine speed, there will be no lock-up.

What causes this problem with the Torque Converter Clutch Circuit Stuck On?

• Transmission fluid level is low
• Transmission fluid is soiled causing restriction in the hydraulic passages
• Fault in the torque converter clutch solenoid valve
• Torque converter clutch solenoid valve harness or connectors are malfunctioning
• Transmission showing Internal mechanical problem
• Defect in Transmission valve body
• Torque converter clutch solenoid valve circuit has become open or shorted

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It is essential to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0742 here:

Common Symptoms

• Check Engine Light in on
• Decrease in fuel economy, this will not affect engine performance
• The Transmission not shifting as usual in or out of a particular gear
• The Transmission may shift but not easily
• The Engine may stall out and die
• The transmission overheats

We have listed out some ways which would help you to correct the occurrence of OBD Code P0742. They are mentioned here as follows:

• Inspect for loose connections and damaged o the transmission wiring harness
• Inspect resistance in the torque converter clutch solenoid as well as the internal transmission wiring
• Repair or replace the transmission control module

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Here are some steps which you should follow in order to diagnose this fault code:

• You will need a OBD code scanner and a DVOM (digital volt/ohmmeter) to be able to diagnose error code P0742. Almost all vehicles with automatic transmission are equipped with some version of computer controlled automatic transmission systems.
• Check if the transmission pressure is sufficient or not to be able actuate gear changes. If there's insufficient fluid pressure present then it could be probably because of low or dirty transmission fluid. It is hence important to inspect the transmission fluid dipstick if you can and fix the issue.
• Ensure that the fluid level is well within the range prescribed by your manufacturer. Also, make sure the fluid is clean and in good condition. Look out for signs of burned smell or abnormalities to be able to judge if the fluid is not compatible.
• If you notice that the fluid is burned, then that’s indicative of transmission operating when the level of fluid was low. This also means that the transmission may have suffered internal mechanical failure because of this. In such a case, you will have to remove the transmission pan and inspect if there are any clutch materials or other debris in it.
• Now move on to look for any burned or shorted wiring and replace circuitry and connectors as per need. You may need to replace the full internal transmission harness if problems are noticed. If you have noticed that all the system wiring, harnesses, connectors and related components are perfectly fine you can proceed to connecting the diagnostic scanner to retrieve all the codes present. Freeze frame the data. Clear all the codes and test-drive your vehicle to see if the code returns or if the PCM enters readiness mode. In case the latter happens, it would suggest an intermittent condition, in which case the problem will have to worsen before proper diagnosis can be made.
• If the code is reset, then take out your vehicles manual and compare the symptoms exhibited and repair accordingly.
• Low pump pressure can be caused due to a clogged hydraulic passage, or a defective pump, fault in shift solenoids or even a malfunctioning electronic pressure regulator. To replace the pump, you will require removal of transmission and partial disassembly as well.
• In case the code has returned and there are no errors in transmission then check for reference voltage and ground signals located at the torque converter clutch lock up solenoid. If you note that the reference voltage/ground circuits are open, then you will have to use the DVOM to check for continuity and resistance in all the circuits. For this, simply disconnect all related control modules from the circuit, only then proceed to checking circuit resistance. Failing to do so, may cause controller damage.
• Now, as per your findings, repair or replace system circuitry, connectors and/or components which aren’t in congruence with the manufacturer's specifications.
• Remember to retest the system and ensure that the repair or installation was successful. When all the system circuits are intact, connect the scanner again to the diagnostic connector and manually activate the torque converter clutch lock up solenoid.
• PCM failure is rare, so don’t jump to conclude it as faulty in this OBD error code. Replacement of the PCM will require reprogramming as well by a professional. If activating the shift solenoid manually fails, then you will have to replace the solenoid or the solenoid pack and then retest the transmission control system.

Common Mistakes When Diagnosing the P0742

In certain cases, there lies a malfunction in the torque converter clutch wiring and they are overlooked. Under this false impression the lock up solenoids/torque converters are replaced when they don’t need to be replaced.