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If you own a vehicle powered by an automatic transmission, it would certainly have a transmission control module or TCM. This is a vital component the transmission utilizes when choosing the ideal gear at any particular time. This article covers what a transmission control module is and the signs of a bad TCM. You will also discover the most efficient way to transmission control module reset.

What is a Transmission Control Module?

A transmission control module (TCM) is a mechanical device that directly controls the power and speed of a vehicle’s transmission. The primary purpose of a TCM is to readily maximize or boost efficiency while enhancing the strength of the wheels. Newer vehicles come with TCMs built into their computers. However, transmission control modules are not infallible and can eventually go bad. When this happens, they cause unreliable and erratic shifting processes and may showcase severe check engine errors.

How to Tell When Your Transmission Control Module Has Gone Bad

When the transmission control module of your vehicle goes bad, you will perceive several signs. You should be aware of these signs because they are crucial. Ignoring them will cause the transmission control module to damage other vital components of your vehicle, resulting in avoidable, costly repairs. Therefore, here are some of the signs you will experience when your transmission control module goes bad: 

  • Delayed Shifting

Poor shifting capabilities or delayed shifts are common problems with automatic transmission. Therefore, if you find yourself downshifting when you are not at high speed or experience rough and jerky starts every time, something could be wrong with the transmission. Changing the transmission control module is the easiest way of dealing with this problem.

  • Poor Fuel Economy

Vehicles powered by an automatic transmission with automatic gearboxes require a lot of petrol in order to run efficiently and smoothly. One of the best ways to check if you have a faulty transmission is by looking at your vehicle’s fuel economy. If it decreases, it simply implies your transmission is no longer working efficiently. You should get your vehicle to an auto repair shop to check for whatever is wrong with the gear system.

  • Difficulty Changing into Higher Gears

The automatic gearbox usually bears the load through 4 different gears whenever you shift. Therefore, the transmission control module is definitely the culprit if you suddenly find it somewhat challenging to shift into a higher gear. You may need to replace the transmission control module and clear every error made in order to restore your vehicle’s smooth operation.

  • Stuck in the Same Gear

This situation can occur when you cannot shift into a particular gear or only keeps going into one gear instead of shifting to another one. This can be disturbing, especially if you’re traveling long distances and need to change your speed from time to time. Therefore, when your vehicle no longer wants to pick up any gears, your transmission control module could be faulty. These common signs show that your transmission control module has gone bad and may require a replacement or resetting. Causes of Transmission Control Module Failure. Your transmission control module can fail for several reasons.

Here are some of the causes of TCM failure:

  • Faulty Wiring

Faulty wiring of TCM circuit boards is quite common in many vehicles powered by automatic transmissions. The wiring may get loose in the connections already made and get worse as it interferes with the smooth functioning of the transmission control module. If left unattended, it can cause the TCM to break down unceremoniously and may require replacement.

  • Heat

When engines operate for a while, they tend to produce heat. However, if the heat is intense, it can cause severe meltdown of some electronic components within the transmission control module circuit board. When this meltdown occurs, the TCM can suddenly fail and require a replacement as soon as possible.

  • Defective solenoid

You will notice a faulty solenoid within the TCM circuit board when you experience abrupt acceleration during driving, irregular starting gear shifts, flat spots, etc. If you find any loose or faulty connection in the solenoid or its components, it will severely harm the TCM, causing abrupt failure. This is one of the primary reasons transmission control modules go bad and require resetting or replacement, depending on the extent of the damage.

  • Voltage Goes into the Circuit Board of the Transmission Control Module

The voltage going unexpectedly into the circuit board of the TCM can cause sudden failure. For instance, the transmission travels up and down at a soft start when starting your vehicle. This results from voltage going to the ICs of the transmission control module, resulting in a burnt-out relay.

Mechanical Consequences

At times, the TCM receives no voltage; when this happens, the component won’t start working. The TCM circuit board can fail as a result. However, heavy vibrations can crush the components of a transmission control module.

How to Reset Your Transmission Control Module

If you want to know how to reset the transmission control module of your vehicle, follow these simple steps one after the other carefully:

  1. Switch off your vehicle’s air conditioner and move the shifter into the ‘Park’ position.
  2. Turn off your vehicle’s ignition and wait patiently for 5 to 10 seconds.
  3. Start the engine and allow it to idle for several seconds
  4. Switch off the ignition and wait patiently for another 30 to 40 seconds.
  5. Repeat these steps 2 to 3 times in order to reset your vehicle’s transmission control module.

This is how to reset your vehicle’s transmission control module efficiently. However, if the TCM is still not functioning properly, you may need to take your vehicle to the nearest auto repair shop for proper diagnostics.


The transmission control module is one of the most crucial components in a vehicle with an automatic transmission. Unfortunately, the TCM can get damaged over time and may require a reset to get it into excellent operating condition. Hopefully, this article teaches you how to reset your vehicle’s transmission control module.

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