Does your vehicle often stall when coming to a stop, exhibit shifting issues, and show signs of reduced fuel economy? Your torque converter clutch solenoid may be at fault. To confirm, run your OBD-II scanner. If it indicates a P0740 Code, use this guide to address the issue immediately.
What Does the P0740 Code Mean?
Diagnostic trouble code (DTC) P0740 stands for “Torque Converter Clutch Solenoid Circuit/Open Circuit Malfunction.” On most vehicles, it indicates that the control module perceives an electrical fault with the torque converter clutch solenoid or the solenoid’s circuit.
However, there are some vehicles for which the code is more indicative of a mechanical problem with the transmission or torque converter.
Note: Although code P0740 is a generic code specified by the Society of Automotive Engineers (SAE), the code’s definition may vary depending on the vehicle manufacturer.
The torque converter is located between the rear of the engine and the front of the automatic transmission. Inside this device is the torque converter clutch (TCC)—a component made up of a friction material that locks the converter shell onto the turbine shaft.
The clutch creates a mechanical connection between the engine and transmission. Applying the TCC reduces engine RPMs, lowers the temperature of the transmission fluid, and increases fuel economy.
The control module uses inputs from various sensors to determine when it is appropriate to apply the torque converter clutch. Once the module deems conditions are correct, it commands one or more TCC solenoid valves to engage the TCC clutch.
On most vehicles, the module will set a P0740 code when it detects an electrical fault with the TCC solenoid or the TCC control circuit.
Also, as was mentioned, on some vehicles, the code may set when the TCC’s performance is out of range due to a mechanical problem.
What are the Possible Causes of the P0740 Code?
A P0740 OBD-II code is a generic trouble code that is supported by many cars. But while this diagnostic code can appear on a variety of vehicles, the steps for diagnosis and repair may vary depending on the vehicle’s make and model.
Listed below are some of the common issues that can trigger a P0740 code:
- Defective transmission converter clutch solenoid
- Electrical fault inside the TCC solenoid circuit
- Faulty torque converter
- Internal transmission failure
- Low transmission fluid level
- Contaminated transmission fluid and/or clogged transmission filter
- Faulty sensor inhibiting proper TCC operation
- Problem with the control module, such as software in need of an update
- Transmission valve body problems
Note: If there are other codes stored in addition to P0740, the causes and symptoms may differ from those listed here.
What are the Common Symptoms of the P0740 Code?
A P0740 code should always be addressed immediately to prevent further damage to the vehicle. It may be unsafe to drive if this trouble code is accompanied by drivability symptoms.
If you experience any of the signs below, make sure to address the issue right away.
Check Engine Light illuminates
A wide variety of problems can trigger the check engine warning light, including an issue with the TCC or related components.
Your transmission may exhibit problems, such as slippage, harsh shifting, and a limited gear range.
If the TCC is stuck on, it may cause the vehicle to stall when coming to a stop.
Shudder felt throughout the vehicle
A TCC that isn’t engaging/disengaging properly can cause a shudder that’s felt at certain speeds.
Reduced fuel economy
Failing to engage the torque converter clutch results in slippage that reduces fuel mileage.
Increase in engine speed
A TCC that isn’t engaging can cause a slight increase in engine RPMs.
How to Diagnose the P0740 Code
Diagnosing and testing your vehicle’s torque converter clutch system can be difficult. It’s best to have a professional troubleshoot the problem for you.
However, if you choose to do the job yourself, the following videos will give you an idea of what’s involved:
How to Fix the P0740 Code
Code P0740 can be caused by anything from a faulty solenoid to a costly internal transmission problem. As such, there isn’t a single, guaranteed fix for the code. To get the code to go away and stay away, you’ll either need to do some troubleshooting or seek a professional diagnosis.
If you do decide to tackle the P0740 code yourself, keep in mind that different types of vehicles may require their own distinct solutions—so always consult the appropriate repair information for your application.
Rely on repair manuals, such as those from Chilton, to get more information on how to resolve the P0740 code. If you want to expand your automotive repair know-how further, consider investing in an ALLDATA single-vehicle subscription.