P0740 Code: Meaning, Causes & How To Fix It

No matter how much experience you have working with cars, the Check Engine Light always causes a moment of fear. You’ll be driving down the road just fine, and that light comes on to ruin your day. If you’ve scanned the engine and gotten the P0740 code, you want to know how to fix it.

In this guide, we explain the meaning of the P0740 DTC. We look at some common symptoms and show you what might be causing the problem. If you want to diagnose it yourself, we have some helpful steps to get you started later in the article. By the time you reach the end, you’ll gain some answers to the questions you’ve been asking. 

Code P0740 Definition

P0740 – Torque Converter Clutch Solenoid Circuit/Open Circuit Malfunction

What Does the P0740 Code Mean?

The P0740 trouble code indicates that the Powertrain Control Module (PCM) detected an abnormal reading from the torque converter clutch circuit. Usually, the PCM goes through numerous checks and the reading needs to be abnormal for a specified amount of time before the light comes on.

This code is considered generic and universal. However, some manufacturers don’t list it at all and some others change the meaning slightly to mean something different. For that reason, it’s best to look up manufacturer-specific codes based on what type of vehicle you drive. 

What Are The Symptoms Of P0740?

The most obvious symptom will be the Check Engine Light. Along with this, you may notice several transmission or engine performance problems. Here are some to look out for.

• Check Engine Light
• Erratic shifting
• Transmission shifting harshly
• Car doesn’t move because the torque converter clutch won’t engage or disengage
• Engine stalls
• Transmission overheats
• Reduced fuel economy

What Are The Causes of P0740?

Because this trouble code has to do with the torque converter clutch, it’s common to assume that is the faulty part, but there are many other possible causes. Here are a few to consider.

• Defective torque converter clutch solenoid
• Malfunctioning torque converter
• Electrical malfunction
• Improper transmission fluid level
• Internal transmission damage
• Faulty PCM

How Serious is the P0740 Code?

Severe – The P0470 trouble code can be caused by serious issues. At any moment, the car can stop running and leave you stranded. 

It’s also possible to experience such severe performance problems that it can affect how you drive. If the car is shifting erratically in a lot of traffic, you could easily cause an accident.

Beyond that, driving your car with this problem will only lead to further damage. You could cause serious damage to the transmission, leading to much higher repair bills. 

How Do I Fix the P0740 Code?

The only way to fix the problem is to know what’s causing it in the first place. For that, a complete diagnosis is needed. If you can’t do it yourself, take the car to a qualified mechanic. Otherwise, we list a few helpful steps below. 

Here are some common fixes you may need to perform.

• Replace torque converter clutch solenoid
• Replace torque converter
• Repair electrical malfunction
• Add/change transmission fluid
• Replace or rebuild the transmission
• Update/replace PCM

Common P0740 Diagnosis Mistakes

It’s easy to make mistakes while diagnosing the P0740 trouble code. Many mechanics want to assume that the torque converter is damaged simply because that’s the part listed in the description.

If you do the same, you could replace a part that is good, costing you more money than necessary. This would be a shame if you only needed to top off the transmission fluid. For this reason, we always recommend walking through the diagnostic steps to determine what’s wrong before replacing parts. 

How to Diagnose the P0740 Trouble Code?

If you have a compatible code scanner, you can easily start the diagnostic process. Sadly, you need more than the free code scan service offered by your local auto parts store. Follow these steps to get started.

1. Check for other DTCs. If there are other codes, you may be able to piece them together to figure out what’s wrong. 
2. Check the transmission fluid level and top it off if needed. You should also check the quality of the fluid. If it looks contaminated or old, change the fluid. Compare it against a transmission fluid color chart to see where it stands. 
3. Look at the transmission wiring harness to see if there’s any corrosion, fraying or damage. If you notice trouble with a connector or wire, replace it. 
4. If you have a digital multimeter, you can run some further tests. Start by finding the wiring diagram for your vehicle in the service manual.
5. Touch the multimeter to the pins that correspond with each side of the clutch solenoid circuit and the transmission’s internal harness or transmission control module. Check all of the connections to ensure the appropriate amount of ohms. 

If you need to perform a diagnosis beyond what we’ve outlined, you may want to visit a mechanic. Some of the steps can get more complicated and they aren’t necessarily for the untrained. When dealing with the transmission, it’s best to avoid causing any more damage. 

How Much Does It Cost To Fix Code P0740?

Once you’ve walked through the diagnostic steps, you should have a better idea of what needs to be fixed. Your next step is to determine what that fix might cost. On average, we have some estimates that include both parts and labor. However, if you can perform the repair yourself, the cost might be lower. 

• Replace torque converter clutch solenoid – $55 to $555
• Replace torque converter – $450 to $1,550
• Repair electrical malfunction – $50 to $550
• Add/change transmission fluid – $50 to $350
• Replace or rebuild transmission – $1,250 to $5,500
• Update/replace PCM – $550 to $2,500

A Mechanic’s Tips About The P0740 Code

Along with the P0740 trouble code, you may notice several others in your reader. These could include the following:

• P0741: Torque Converter Clutch Solenoid Circuit Performance/Stuck Off
• P0742: Torque Converter Clutch Circuit Stuck On
• P0743: Torque Converter Clutch Solenoid Circuit Electrical

Most of these codes have the same symptoms, causes and fixes related to them. You would want to run through the same diagnostic steps. 

With all of these codes, there’s a simple way to prevent problems. By changing the transmission fluid and filter at recommended service intervals, you ensure that the internal parts of the transmission get the lubrication needed. This simple step keeps the transmission running at its best, so there are fewer problems with the torque converter. It also keeps debris from creating a restriction that could cause serious issues. 

Conclusion

With the P0740 trouble code set in your car’s computer, you need to take swift action. It’s important to get to the bottom of what’s going on, so you can avoid permanent transmission failure. If you’ve ever priced out the cost of a rebuilt or used transmission, you know this is something you don’t want to deal with.

If you have some basic tools, it’s not hard to do a little diagnostic work on your own vehicle. However, if you ever feel overwhelmed or unable to complete the process, it’s best to take it to a mechanic. We would rather see a car come into the shop than someone try to work on it and cause more problems.