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Transmission Control Module Symptoms: Learn the Bad Ones

The transmission control module is the driving force behind the mechanism of an automatic transmission. It’s a small component but is absolutely necessary for the efficient functioning of the transmission. When this little device wears out or gets damaged, your car struggles with a downgraded performance and driving becomes a chore rather than fun. There are several transmission control module symptoms that alert you that something has gone wrong and the most likely culprit is the module.

What Is a Transmission Control Module?

What keeps a car running? The transfer of power from the engine to the wheels. 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 to convey the received signals to the clutch, which then execute the orders by making necessary changes to the fuel usage and power production.

what is a transmission control module
The control module of a 1997 Jaguar XK8 Transmission. (Photo Source: amazon)

There are some computerized modules that have internal memory to remember information for your driving habits and apply it to make the correct gear adjustment. You should be alert for bad transmission control module symptoms because malfunctioning one will affect the car’s performance.

Transmission Control Module Symptoms You Should be Alert of

Signs of a bad transmission control module is not hard to pick up if you know what they are. 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 transmission module symptoms to warn you that the device is not working properly.

The car has to shift through various gears with the precise timing in order to speed up, and the module is component that is mainly responsible for this operation. An acceleration delay means that it has gone bad and needs a 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
bad transmission control module symptoms
The gear shifting problem could be a dangerous one. (Photo Source: istockphoto)

These are all 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 easier to keep track of whether the car is burning more fuel than necessary.

Is It Safe to Drive with Transmission Control Module Symptoms?

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.

signs of a bad transmission control module
It is never safe to drive with a transmission issue. (Photo Source: cars)

Also, keep driving with a bad transmission is not going to fix it. Rather, it will deteriorate the condition and your transmission can end up grinding itself to pieces.

What Is the Solution?

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 problem. You 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.

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  4. Mark says

    Hi, I have a 2010 Mazda 3. I took it to the Mazda dealer and had the car checked. They said it is the Transmission Control Module. Total price with installation is $1200.00. The car wont drive in 1st gear. Is there a safe gear to drive it to the dealer? Ive heard there is a safe gear but i dont know what it is. Thanks! Mark

    1. Mark says

      I guess nobody knows the answer… I was going to sign up on here too…

    2. Ed says

      I have the same issue with my daughters 2011 Mazda 3. It appears as though it’s stuck in 3rd gear, will not change to 1st at a standstill and won’t go up into 4th. If the dealer is close you could drive it but I’d suggest calling a tow truck. I am doing the TCM replacement myself in my garage but it will still cost me $715 (part plus tax)
      What makes me mad is that Mazda has had years of this same TCM failure issue yet they expect the owners to pay! A TCM is not a part that wears out and should not fail. My daughters car only has 117,000 km and already I got an Evaporator leak code and now this TCM issue. Never again will I purchase another Mazda. Good luck with the repair.

      1. Mark says

        Thank u so much for the reply Ed. Ill keep u updated. Will probably try to install it myself. Ill update u. Thanks!!!

  5. Michael Wascher says

    My friend has a 2005 Suzuki Aerio, and it has a no start issue. The car cranks but won’t run, I found a blown ignition fuse #8 which also powers the TCM, I found it below the radio on the floor. It’s found on eBay used for $88. I opened up the module and 3 of the capacitors were burnt to a crisp.

  6. Andy says

    Hello, I have a 2010 Toyota Aygo 1.0 petrol automatic car. A couple of weeks ago the transmission stopped working and the red trabsmission warning sign was illuminated. They replaced the solenoid and the electornic control unit, it costs $2500. Now they say that the car drives OK, but it stops working after it warms up, and we have to replace the transmission control computer, too. Is this possible that bot units failed, or they are trying to cheat us and charge more for the work? I am suspicious. Thks

  7. jeff says

    i need to locate my gearbox control moduel as it has become faulty but no one can find it its a 2005 mitsubishi colt 1.5 did auto anyone know where the gearbox control moduel would be found in the car

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