Transmission Control Module Symptoms: Learn the Bad Ones

There are several bad transmission control module symptoms that alert you that something has gone wrong and the most likely culprit is the module. 

When this little device wears out or gets damaged, your car struggles with a downgraded performance and driving becomes a chore rather than fun.

What Is A Transmission Control Module?

The transmission control module is the driving force behind the mechanism of an automatic transmission. It’s a small component but is necessary for the efficient functioning of the transmission. 

 The transmission performs the main role in transferring that power and the module is the component that controls the transmission. You will find this little component on the rear side of the engine.

Based on the information it receives from the engine, the module is the key to shifting the gears and changing the speeds. 

What it does is convey the received signals to the clutch, which then executes the orders by making necessary changes to fuel usage and power production.

tcm on car
The control module of a 1997 Jaguar XK8 Transmission. (Photo: Amazon)

Some computerized modules have internal memory to remember information for your driving habits and apply it to make the correct gear adjustment.

You should be alert for several faulty transmission control module signs because malfunctioning one will affect the car’s performance.

Bad Transmission Control Module Symptoms You Should Be Alert of

After knowing the transmission control module location and its function, let’s follow along to find out what happens when a transmission control module goes bad?

Signs of a bad transmission control module are not hard to pick up if you know and understand what they are or where they come from. 

Here are some transmission control module problems that you should never ignore:

Performance Issues

Is your car showing a delay in acceleration when you press the pedal? Is it not picking up the speed the way it used to? It could be one of the bad tcm symptoms to warn you that the device is not working properly.

The car has to shift through various gears with precise timing to speed up, and the module is the component that is mainly responsible for this operation. An acceleration delay means that it has gone bad and needs fixing.

Problems with Shifting

There could be several shifting issues, warning you about bad transmission control module symptoms. Some of the most common glitches are:

  • Not doing the downshift correctly when the car stops at a traffic light
  • Delayed response when shifting out of a lower gear during acceleration
  • Shifting to a neutral gear without a warning
  • Being unable to shift out of the neutral mode
  • Random shifting from one gear to another
  • Accelerating slowly or getting stuck while driving uphill
symptoms of a bad tcm
The gear-shifting problem could be a dangerous one. (Photo: iStockphoto)

These are all bad transmission control module symptoms, indicating a problem with the component. 

Although, you can easily check if the module is the source of trouble if there is a manual override. There will be no doubt about it if you can move to the right gear manually.


Struggling with Fuel Efficiency

One of the notable signs of a bad transmission control module is lower fuel economy. A transmission hitch means the engine has to work harder when crossing some rough tracks or getting up a mountainous road. 

When it happens, the car is likely to burn more fuel than usual. If the frequency of your trip to the gas station increases without any apparent reason, the problem could be with the transmission module

Many automobiles these days have an info display, showing the current fuel economy with some other variables. It makes it easier to keep track of whether the car is burning more fuel than necessary.

Cars stuck at Limp Mode

One noticeable and aggravating indication of a malfunctioning TCM is your vehicle becoming trapped in “Limp Mode“. 

Most cars activate this self-preservation mode when the TCM identifies a significant problem with the transmission, provides incorrect data, or simply ceases interacting with other control modules within the vehicle.

Limp mode, in effect, inhibits the automobile from moving to higher gears, restricting the power and speed of your vehicle.

What Causes Bad Transmission Control Module Symptoms?

Here are some reasons why the transmission control module is failing. 

Wear & tear

The older your car gets and the more miles you put on it, the more parts wear down and fail. Weather, road conditions, foreign chemicals that corrode, and a lack of maintenance all add to wear and strain. 

car wear and tear
The longer you own your vehicle, the more it will decay and fail. (Photo: ZenAuto)

Engine heat generated

Because the transmission control module is a computer composed of electronic components, it is susceptible to heat damage. 

Heat is never good for electronics, including TCMs. The metallic and plastic encasing of your TCM is intended to protect it from heat, but it can fail.

Vibrated ride

Vibration is also bad for electronics, and autos vibrate a lot. The engine produces vibration, which rises with speed and RPMs. 

Your vehicle vibrates as a result of road bumps. This research essay explains why vibration is so detrimental to the TCM and its bracket.

What Are The Solutions?

A transmission control module is an electronic device and a burnt circuit is the reason for its failure in most cases. 

It can be a faulty resistor or transistor on a printed circuit board. Any qualified technician or an experienced car mechanic can fix the problemYou can even replace the entire module if necessary but the device is expensive.

The good news is sometimes the issue is not with the module despite the car showing these similar symptoms. Instead, a blocked passage or a faulty valve solenoid in the transmission could be the culprit. 

The module cannot work properly because it does not get the correct voltage supply due to issues with these parts. In that case, you can just replace that problematic device and have the issue fixed at a lower cost.

Can You Drive With A Bad Transmission Control Module?

Not at all! A problem with the transmission, especially with shifting gears, means that the car can randomly move into another gear or does not move into the right gear while you are driving. 

Both situations can be dangerous whether you are driving in the city or on the highway.

tcm replacement cost
It is never safe to drive with a transmission issue. (Photo: Pixabay)

Also, driving with an errored TCM in cars is not going to fix it. Rather, it will deteriorate the condition and your transmission can end up grinding itself to pieces.

FAQs on Transmission Control Module

1. Can a bad TCM cause transmission slipping?

Yes, a malfunctioning TCM can lead to transmission slipping. When the TCM fails to regulate gear shifts properly, it can result in gears not engaging or disengaging as they should, leading to slipping, poor acceleration, and reduced power.

2. How do I know if my TCM is causing gear shifting problems?

If you experience abrupt or delayed gear changes, even at normal driving conditions, your TCM could be the culprit. Unusual noises, such as clunking or whining, during gear shifts can also be indicative of TCM problems.

3. Will a bad TCM trigger the “Check Engine” light?

Yes, a failing TCM can trigger the Check Engine light to illuminate on your vehicle’s dashboard. Modern vehicles are equipped with onboard diagnostics that detect TCM-related issues and generate error codes.

4. Can a bad TCM lead to transmission overheating?

A malfunctioning TCM can contribute to transmission overheating. Incorrect gear shifts and slipping gears caused by a bad TCM can generate excess heat within the transmission, potentially leading to overheating.

5.  Can a bad battery cause TCM problems?

A weak or faulty battery can impact the TCM’s performance. Voltage fluctuations can disrupt the communication between the TCM and other control modules, leading to erratic behavior. It’s a good practice to ensure your vehicle’s battery is in good condition.

Final Words

We have just scrolled through some bad transmission control module symptoms and the solutions to each of the circuits. Hope you find this piece of information helpful and see you later with more car maintenance tips with Car From Japan.