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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.”  Take note that many vehicles don’t even list this as a possible code. But on vehicles that include P0740, it indicates that the control module (PCM or TCM – Transmission Control Module) perceives an electrical fault with the torque converter clutch solenoid or the solenoid’s circuit.

torque converter model
Diagnostic trouble code (DTC) P0740 stands for “Torque Converter Clutch Solenoid Circuit/Open Circuit Malfunction.”

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. 

For an in-depth, technical discussion of how P0740 is triggered, read the next section.

If you want to learn the possible causes of P0740, click here.

How Code P0740 is Triggered

The torque converter is located between the rear of the engine and the front of the 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. 

torque converter of a vehicle
The torque converter is located between the rear of the engine and the front of the transmission.

The clutch creates a mechanical connection between 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. Since about 1990, most vehicles engage their torque converter clutches in stages leading up to 100 percent lockup. That means the solenoid is designed as a “variable force” solenoid that provides varying amounts of pressure to the converter clutch as commanded.

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. 

A 2006 Explorer, for example, defines the P0740 as “TCC circuit fails to provide voltage drop across solenoid. Circuit open or shorted or PCM driver failure during on-board diagnostics.” 

It’s a simple matter for the ECM/TCM to measure the continuity of any solenoid on the controlled side of that coil. On a solenoid that is hard-wired to power, the ECM/TCM looks for 12 volts at the controlled side of the solenoid whenever the solenoid isn’t energized (grounded). On a solenoid that is hard wired to ground, that same strategy works, except that the ECM/TCM is looking for ground on the controlled side of the deenergized coil rather than power.

But as was mentioned earlier, on some vehicles, the P0740 code may set when the TCC’s performance is out of range due to a mechanical problem. 

To search our database for other OBD2 codes, click here.

What are the Possible Causes of the P0740 Code?

asian mechanic checking on car hood for possible problems
While P0740 code can appear on a variety of vehicles, the steps for diagnosis and repair may vary depending on the vehicle’s make and model.

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 
  • 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
man pouring transmission oil in car engine
Low transmission fluid level is one of the possible causes the P0740 code.

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

check engine light flashing indicates a problem in car
An issue with the TCC or related components can trigger the check engine warning light.

A wide variety of problems can trigger the check engine warning light, including an issue with the TCC or related components. 

Shifting problems

Your transmission may exhibit problems, such as slippage, harsh shifting, and a limited gear range. 

Engine stalling

frustrated man looks at the idle car engine
Your vehicle may stall when coming to a stop if the TCC is stuck on.

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

car tachometer with high turnover
A TCC that isn’t engaging can cause a slight increase in engine RPMs.

 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.

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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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