Torque converters - [2023] overview

You might have heard or seen a discussion on the most complex part of a modern-day vehicle. This article addresses the torque converter clutch solenoid which acts as the brain behind the converter clutch.

Every vehicle has a device located between the back of the engine and the forward part of the transmission. This device is called the torque converter, and it transmits the engine's power and torque to the vehicle transmission.

Another function of the converter includes the prevention of slipping when the vehicle reaches high levels of speed. To achieve this, it needs to lock the engine and the transmission into a direct drive. It does this so that the engine and transmission can rotate at the same rate.

What is a torque converter

A torque converter clutch is a component responsible for locking the engine and transmission. Once it does this, the converter becomes capable of transmitting 100% of the engine's power to the transmission.Inside the torque converter, you will find transmission fluid that flows from one end of it to the other. Its pressure regulates the application and release of the converter clutch.

This pressure is, in turn, under the control of the torque converter clutch solenoid.

What is the torque converter clutch solenoid?

Torque converter clutch solenoid

The clutch solenoid is responsible for controlling the pressure of the transmission fluid. It does this by moving the valve that sends the pressurized fluid to the converter clutch's circuit. There is a transmission control module (TCM) and a powertrain control module (PCM).

They control the opening and closing of the torque converter clutch solenoid valve. You can see the torque converter clutch (TCC) solenoid as the converter's component that handles the signals that dictate the locking and unlocking of the TCC solenoid valve.

Torque converter clutch solenoid circuit

Torque converter clutch solenoid circuit

Being a component that converts electrical energy to mechanical, the TCC solenoid has an inbuilt circuit of its own. This circuit plays a vital role in helping the solenoid carry out its function of responding to signals. The circuit receives the signal (in an electrical form), interprets it, and converts it to mechanical energy that the rest of the torque converter clutch can understand and use.

Now, this circuit has a diagnostic trouble code, which is the P0740 code. The code represents torque converter clutch solenoid circuit/open circuit malfunction. It calls the driver's attention because the control module has taken note of an electrical fault in the solenoid or the solenoid circuit.However, in some cars, the code stands for a mechanical issue with the torque converter or the vehicle's transmission.

Put it at the back of your mind that the code might vary in meaning based on the vehicle manufacturer.

The P0740 code

Torque converter clutch solenoid

This code is a common trouble code that many vehicles support. However, while you will find see it appear on several vehicle types, the steps involved in diagnosis and repair vary from model to model and manufacturer to manufacturer.

Issues that can trigger the P0740

While several issues and factors out there can trigger the code, this section gives the more common ones.

Faulty torque converter

A damaged or malfunctioning torque converter can trigger the code to appear. This code will alert the driver to take the vehicle to the repair shop if something gets damaged.

Transmission valve body problems

If the transmission valve body gets damaged, the P0740 code will appear.

Misbehaving transmission converter clutch solenoid

The code can also appear if the torque converter clutch solenoid itself should get damaged.

Low level of the transmission fluid

When the transmission fluid in the torque converter becomes low, the code will appear.

Damaged sensor inhibiting proper TCC function

Our article on the torque converter clutch will find a section where we highlighted the various sensors that help the valve function. You can access the article by clicking on this link. A damaged sensor will also prompt the code to appear.

An electrical fault inside the torque converter clutch solenoid circuit

When the circuit develops a fault that prevents it from carrying out its function properly, the code will appear.

Failure of the vehicle's internal transmission

A failure in the internal transmission of the vehicle remains likely to trigger the P0740 code.

Clogged or contaminated transmission fluid

Apart from a case where the transmission fluid falls below a given level, it can trigger the code to get clogged. Clogging could occur due to debris or broken metal chips that fall off when the torque converter gets damaged.Also, if the transmission fluid should get contaminated, the code will appear. Simply having it flushed out and changing the fluid should settle this issue.

Software update

Yes, the code can be trigger if there is an available update for the control module's software.

The P0740 code – common symptoms

The P0740 code – common symptoms

Professionals highly recommend that one should always react to a P0740 code as soon as possible. But how do you know the signs that point this fault out to you? This section answers that question!

Engine speed increase

When a vehicle's torque converter clutch becomes unable to lock the engine and transmission in direct drive, it can affect the engine speed. An increase in the engine's rotations per minute (RPM) remains one of the signs of a damaged clutch.

The engine light

When you see the check engine light indicator come on, do well to check it out as soon as you can. It might turn out to be something more.

Limited gear range

The vehicle's transmission might begin to experience issues like limited gear range and harsh shifting.Our article on the symptoms of a bad torque converter highlights and explains more of these signs. You can find the article by clicking this link.

Key takeaways

Concerning the torque converter clutch solenoid, this section covers the major things covered in this article.

  • The torque converter clutch solenoid controls the pressure exerted by the transmission fluid on the torque converter clutch.
  • A TCC solenoid converts electrical signals to mechanical ones that prompt the converter clutch to engage and disengage appropriately.
  • The opening and closing of the TCC solenoid valve are controlled by the transmission control module (TCM) and a powertrain control module (PCM).
  • The TCC solenoid circuit can develop a fault represented by an error code that alerts the vehicle driver. Manufacturers refer to the code as the P0740 code.
  • Encountering the P0740 code means that one or more of several faults might be responsible. The faults are highlighted above in the article.

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