How to Fix Code P0740 in Your Vehicle

Code P0740 is a headache for many mechanics and car enthusiasts. If your OBD-II scanner has shown this code, it’s time to understand what it means and how to fix it. In this article, we’ll break down the issue so you can diagnose and repair it without hassle.

What Does Trouble Code P0740 Mean?

Trouble code P0740 indicates a problem with the "Torque Converter Clutch Circuit" (TCC).

Basically, it means that the transmission isn’t properly locking the torque converter, which can lead to reduced efficiency and increased fuel consumption.

The TCC is responsible for locking the torque converter when the car reaches a steady speed, allowing for more efficient driving. If the system detects that the clutch isn’t functioning correctly, it will trigger code P0740.

In simple terms, the torque converter is slipping more than it should, negatively affecting the vehicle’s performance.

Which Vehicles Are Most Commonly Affected?

Although code P0740 can appear in any vehicle with an automatic transmission, it’s most commonly seen in:

• Honda and Acura (2000–2015) – Especially Accord, Odyssey, Civic, and TL.
• Dodge and Chrysler (2005–2014) – Models with the 41TE transmission and similar ones.
• Toyota and Lexus (1998–2012) – Particularly in Camry, Sienna, and Corolla.
• General Motors (Chevrolet, GMC, Cadillac) – With 4L60E and 4L80E transmissions.
  

If you have one of these vehicles and your scanner shows this code, pay attention to the symptoms and causes.

What Causes Code P0740?

There are several reasons why code P0740 may appear:

• Low, contaminated, or burnt transmission fluid. Poor fluid condition won’t properly lubricate the transmission’s internal components and can cause TCC failure.
• Faulty or stuck TCC solenoid. This component controls the engagement and disengagement of the torque converter clutch.
• Damaged wiring or loose connections. Poor electrical contact can disrupt proper TCC operation.
• Malfunctioning Transmission Control Module (TCM). A failing TCM can send incorrect error codes or cause TCC operation issues.
• Mechanical failures in the torque converter. Internal damage may prevent the TCC clutch from locking properly.
• Clogged transmission filter. A blocked filter can restrict fluid flow, impacting the solenoid and TCC.
• Internal transmission damage. Worn components from abuse or even collisions can also be to blame.
  

Symptoms of This Trouble Code

If your car has code P0740, you may notice:

• Increased fuel consumption, since the transmission isn’t locking efficiently.
• Unstable RPMs while maintaining constant speed due to improper torque converter lock-up.
• Difficulty shifting gears, especially at highway speeds or steady cruising.
• Transmission overheating, since the lack of TCC lock-up creates extra friction and heat.
• Check Engine light illuminated, along with code P0740 in the OBD-II scanner.
  

How to Diagnose Code P0740

1. Scan the car using an OBD-II tool to confirm the code.
2. Check the transmission fluid—if it’s dark or burnt, this may be the cause.
3. Test the TCC solenoid with a multimeter.
4. Inspect wiring and connectors.
5. Perform a road test to check for slipping or torque converter lock-up failure.
   

Common Diagnostic Mistakes

• Replacing the entire transmission without checking the solenoid first.
• Ignoring the condition of the transmission fluid.
• Failing to inspect wiring before spending money on major repairs.
• Assuming it’s just an electronic issue without ruling out mechanical failures.
  

How Serious Is It?

Code P0740 can affect fuel efficiency and, over time, damage the transmission if not addressed. While it’s not something that will cause the car to stop immediately, ignoring it can lead to costly repairs.

How to Fix It

Depending on the cause, solutions may include:

• Changing Transmission Fluid and Filter
  Flush the transmission using the correct fluid. Fresh fluid may eliminate the code. It’s likely the code will reappear after being cleared, but it may not trigger the Check Engine light. To fully clear the code, you’ll need to connect the car to a factory scanner.
• Replacing the TCC Solenoid
  This part controls fluid flow inside the torque converter and affects transmission performance. Replacing the solenoid could solve the issue.
• Repairing Wiring or Connectors
  Damaged, frayed, or exposed wiring can cause this trouble code to appear.
• Reprogramming or Replacing the TCM
  It’s important to determine whether the TCM is at fault. A faulty TCM can cause many other issues or be connected to them.
• Repairing or Replacing the Torque Converter
  The torque converter and its clutch are crucial components that transfer power from the engine to the wheels. These parts can become damaged over time.
• Replacing the Entire Transmission (Extreme Case)
  This should be a last resort. If not a full replacement, individual components worn out over time will need repair. It’s the most expensive solution but ensures long-term reliability.

Code P0740 isn’t the end of the world, but it’s not something you should ignore either.

With a proper diagnosis and the right fix, you can prevent further damage and keep your vehicle running smoothly. If you’re a mechanic or car enthusiast, following these steps will save you time and money on unnecessary repairs.

At Sun Transmissions, you’ll find the parts you need for your automatic transmission. Including rack and pinion seal kits. Get what you need and enjoy free shipping on orders over $90. 

If you have questions or need help navigating our site, contact us via WhatsApp.