How Do You Reprogram A Transmission Control Module

Knowing essential information about your car and how it operates is always a good idea, especially if you are caught in a tight spot with no one to rely on but yourself. 

A general understanding of some of the car’s basic parts will always prove useful in identifying common problems that might occur along the way. 

We want to talk more about TCMs or transmission control modules in this article, or for example, how you reprogram a transmission control module. It’s a very important piece of the car, without which automatic shifting cars would not be able to function. 

What Is a Transmission Control Module

A TCM is a little piece of PCB(Printed Circuit Board) responsible for monitoring the cooperation between the engine and the automatic transmission in a car. Its job is to determine the best time to change gears so that the entire ride can be as smooth and pleasing as possible. 

The TCM is also responsible for sending diagnosis signals when it senses something is wrong with the engine and the transmission. It does that by sending OBD2 codes to the car’s computer. 

Recognizing a Broken Transmission Control Module

Even though a TCM is a piece of the car that is high-quality and built to last, nothing lasts forever. So when the car starts behaving strangely, you should be able to determine if maybe the TCM is causing the problems. These are the several things that may indicate you have a faulty Transmission Control Module unit.

Reasons why the Transmission Control Module could fail

Automatic transmission cars are much more complicated than manual ones because they require computers and high-end sensors to operate properly. Because of the involvement of computers in the process, the TCM is most commonly damaged by some kind of electrical failure derived from:

  • A short circuit in the actuator or solenoid
  • A short circuit caused by moisture or water
  • Abnormal vibrations of the car, while driving on a bumpy road, for example
  • A high-voltage overload

The check engine light on your car will be constantly lit

The first thing that might indicate a problem with your car, in general, is a check engine light that is constantly on. The check engine light may also indicate other problems, but your TCM board is most likely at fault when paired with the symptoms described below.

Apparent problems with the car’s transmission

When a faulty TCM unit is the culprit, the car’s transmission will begin to act erratically. That means it might slip and not engage properly while driving, and the car will begin to lose power as it cannot reach higher speeds. The car will be unable to upshift or downshift properly, resulting in an unpleasant driving experience. 

Another sign within the transmission is a discoloration of the transmission fluid because of excess heat due to the constant slipping. Checking the color of the transmission fluid can be an important clue when diagnosing a faulty TCM unit. 

Frequent refueling

Modern cars with automatic transmissions use computers to calculate every operation and movement inside the engine. They use sensors for everything, so the car’s computer can precisely calculate how much fuel it needs to produce the optimum results at the lowest consumption rate.

Because most cars are economical, you should know how much fuel your car uses per 100km. If you experience a frequent need to refuel, however, the car is not as it should be, which means more power is wasted because a faulty TCM is not operating the transmission properly. 

How Much Would It Cost to Replace Or Repair a Transmission Control Module

Once you properly diagnose the problem and establish that it is indeed a faulty TCM, you have two choices: replace it with a brand new one, take it to a certified repair shop to be reprogrammed, or try reprogramming it yourself.

If you decide to replace the TCM unit with a brand new one, we advise you to take your car to a repair shop and have the people there do it for you. This is the most expensive option, costing anywhere between $500 to $900. The module costs between $450 to $750, while the rest you will have to pay for the mechanic’s labor.

Reprogramming the installed module costs less, and you should expect to pay around $300 to the mechanic to have it fixed.

We would advise trying to reprogram the module yourself first, and if that does not work, then you can try taking it to be repaired to a certified repair shop. Below we will cover the steps in which you can try and reprogram the module successfully.   

How Long Is the Reprogramming Going to Take

Whether you take your car to the repair shop to reprogram the Transmission Control Module or try reprogramming it yourself, the entire process should take anywhere between 30 to 60 minutes. 

The repair shop might do it even faster because they may have special equipment to reprogram the module more quickly and easily. The downside to taking your vehicle to a repair shop is that it could be busy, so you would have to wait a while for your car to be fixed. 

How Do You Reprogram a Transmission Control Module Successfully

Before you start reprogramming the Transmission Control Module yourself, we will note that if unsuccessful the first time, you should give it a couple more tries. It is more likely that you will fail the first time you try to reprogram the module because you are unaware of what to expect in the process, so be patient and try again if nothing improves. 

We tried to break the entire process into simple and intuitive steps, detailing each and telling you what to do and expect while reprogramming the module. The process may vary depending on the car model, but we could determine the most common steps that apply to almost all car models. So, how do you reprogram a transmission control module? It’s easy; just follow these few steps:

1. First, turn the ignition key to the second position

Before starting the reprogramming sequence, the first thing is to ensure the car is not running, and you switch the key in the ignition in the second position. 

While the key is in this position, the dashboard inside the car’s cabin should light up, indicating that the car’s engine is ready to start. There should be two clicks coming from the dashboard. You might also hear a click or a buzzing sound, which differs from vehicle to vehicle, but that is usually the abs and the airbag getting ready. Don’t start the car yet! 

2. Second, apply pressure on the gas pedal

The next thing to do is apply gentle pressure on the gas pedal, just like you would when driving. Make sure to press the pedal down and a little to the side. This will make the kick-down switch turn on. 

After pressing the pedal down, hold it in that position for about 15 to 20 seconds. You should also hear a click while holding the pedal. 

3. Third, wait it out

After holding the gas pedal for 15 to 20 seconds, turn the key in the ignition to the off position but don’t let go of the pedal before you do it! 

After you turn the key off, you can raise your foot from the pedal and wait for the next step. It is important to leave the key inside the ignition, not touch anything in the car, and don’t even open the doors. 

Stay still and be patient for about five minutes, the average time for most Transmission Control Modules to reset. Remember that all the steps so far were to reset the module to its factory settings. 

4. Fourth, take your car out for a spin!

After five minutes, the final step is to take the car out for a spin. Make sure that you drive for at least 30 minutes, so the newly reset Transmission Control Module can have time to pair with the engine control module. You will be teaching your car the way you drive.

Make sure you don’t make any sudden accelerations or break while driving your car after resetting the TCM. Just drive normally and patiently, and feel how the car is shifting between gears. Everything should be smooth and without any kicks or jerks. 

If you feel satisfied with how the car runs, then congratulations, you’ve just successfully reprogrammed your TCM!

Final Thoughts

A defective TCM can present a serious problem to the car and its owner. If left unchecked, it can damage other parts of the car and leave you with unexpected and quite costly expenses to deal with.

But we hope that with the information we provided in this article, you will never again wonder how do you reprogram a transmission control module since you’ve learned all you need to know to fix it, anytime and anywhere!

Liam

Hi, I'm the initiator and writer of this blog. Cars were and will be my first love, and my favorite hobby, that's why I decided to start this blog and write about my discoveries and techniques to improve my cars or repair them.