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OBD2 Code P0742 and How to Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

The transmission control module (TCM) has detected a strange problem with the torque converter clutch circuit (TCC).

Meaning

The TCC creates a one-to-one connection between the engine and the transmission. This connection ensures that the car runs smoothly and gets good gas mileage. Without the TCC, the engine would have to work a lot harder to generate forward momentum.

If the TCC slips, that can trigger code P0742. However, it usually happens a few times before the check engine light comes on, as slight slippage can occur on occasion. 

Causes

Because the TCC bridges the engine and the transmission, there are several potential reasons for slippage and a problem code, such as: 

  • Dirty Transmission Fluid - As this fluid accumulates dirt and other particles, it doesn’t work as efficiently. 
  • Low Transmission Fluid - Your car’s engine needs transmission fluid to engage the various gears as it shifts. If there isn’t enough liquid, this shifting can be affected, causing a problem with the TCC. 
  • Faulty Torque Converter Clutch Solenoid Valve - This valve controls the flow of transmission fluid into the TCC. If the valve isn’t working correctly, it can affect this transfer. 
  • Internal Mechanical Problem With the Transmission - Even if the TCC, solenoid valve, and transmission fluid are all working correctly, the transmission itself may have a problem. Some of these issues can affect the TCC and create slippage. 
  • Faulty TCC Solenoid Valve Harness - This harness keeps the solenoid valve in place, but it can come loose and stop working. 
  • Faulty TCC Solenoid Valve Circuit - This circuit prompts the valve to open and close at the right times. If the circuit is damaged or open, it won’t control the flow of transmission fluid correctly. 

Symptoms

In many cases, a faulty torque converter clutch may not show any symptoms while driving. The TCM sensor is highly sensitive, meaning it can detect minor slippage before it becomes a huge problem. 

In severe cases, slippage could cause a noticeable loss of momentum while the car is shifting between gears. It may take a second or two to engage the next gear, making it feel like the car is revving in neutral. 

Another symptom of this problem is an overheated transmission since the engine has to work harder to transfer forward motion. 

Diagnosis

The best way to diagnose this problem is to reset the check engine light and drive the car for a while. If the light comes back on, you know that the issue wasn’t a fluke. 

From there, you have to rule out the potential causes until you’re sure what the problem is specifically. Start by checking the transmission fluid to see if it’s dirty or low. Next, inspect the TCC and the solenoid for damage. If everything looks good, the problem may be inside the transmission itself. 

Common Mistakes

Overall, it’s best to inspect each potential cause before moving onto the next one. Even if you fix one problem, that may not prevent the light from coming back on. 

After inspecting or fixing a specific part, be sure to reset your engine and drive it for a while to see if the light returns. 

One common mistake is to swap the solenoid and/or its valve, even though the wiring may be faulty instead. 

How Serious Is This Code?

If left untreated, it could damage your car’s engine and transmission and lead to a massive repair bill. Over time, the slippage could get worse, meaning that your vehicle struggles to shift to higher gears. When that happens, the engine can overheat, and parts can get damaged even more. 

Overall, you want to get your transmission and TCC checked out if you discover this code, even if your car isn’t showing any noticeable symptoms. 

What repairs can fix the code

If the transmission fluid is dirty or low, you can start by flushing the old liquid out and replacing it. If the fluid is not the problem, start by inspecting the solenoid wiring for damage or corrosion.

If neither of those issues is responsible, the next step is to replace the solenoid and/or its valve. If that doesn’t fix the code, the problem is likely deeper within the transmission. 

In rare cases, the problem could be with the transmission control module sensor. If it’s faulty, you can replace the TCM. 

Related Codes

Conclusion

Your car’s transmission is like its heart, meaning that if it’s not working correctly, you could experience some significant problems. Any code related to the TCC should be addressed as soon as possible.