How To Replace A Mazda Transmission Control Module

If you have a Mazda, it's important to know how to replace the transmission control module (TCM) if it happens to malfunction or break. In this post, we'll show you how to replace the TCM on your Mazda.

Why It's Important To Replace Your TCM ASAP

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To put it plainly, when your Mazda's TCM fails, your automatic transmission stops working. Your transmission may not be able to shift at all. It'll be stuck at one speed. If it can still shift, it won't shift correctly. Both scenarios can be quite dangerous.

The most common signs of a TCM going bad include:

  • Transmission hesitating between shifts
  • Loss of power upon acceleration
  • Reduced fuel economy
  • Engine shuddering or stalling on the road
  • Engine revving without the car moving
  • Check engine light coming on

If you need to confirm that your TCM is failing, this diagnostic guide may help you.

How To Replace Your Mazda's TCM

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In most Mazda models, replacing the TCM is pretty easy. The first step is finding the TCM in your car.

  • If you have a 2009 Mazda 6, for example, you'll find the TCM behind the passenger side kick panel. The TCM is right above the ECU.
  • If you have a 2010 Mazda 3, you'll find the TCM under the battery tray on the roof of the transmission.
  • In some Mazda models, the TCM is under the battery box. In this case, you need to remove the battery box to access the TCM.

Consult a service manual if you're not sure where the TCM is located.

When you have the TCM in front of you, take the following steps to replace it:

  1. Remove the electrical connector(s) from the TCM. If there’s not a lot of working room, you can do this with a slim/flat tool like a pry tool.
  2. Remove the nuts and bolts securing the TCM in place. Be sure to check both sides of the TCM for the nuts and bolts.
  3. Pull out the old TCM.
  4. Mount the new TCM in place. Make sure it’s fully secured.
  5. Connect the electrical connector(s) to the new TCM.

Next, you want to do a dash readout to ensure that the replacement went well. To do this, start up the car. Check and see if the check engine light is still on. Plant your foot firmly on the brake pedal. Next, change the transmission gears (from park to neutral or drive) and see if the dash responds accordingly. You can take your Mazda out on a test drive, too.

Why It's Important To Get The Right TCM For Your Mazda Vehicle

If you get an OEM TCM that's configured for your transmission, you don't need to program it. It acts as a plug-and-play device.

When looking for a replacement TCM, be sure to get one for your exact transmission. Some of the same Mazda models come with different transmissions. For example, the 2011 Mazda 3 came with a 5-speed transmission. The 2012+ Mazda 3 models came with a 6-speed transmission.

The good news is that looking for the right TCM for your vehicle is pretty easy. All you need to do is look up your Mazda model here. We have a catalog of genuine OEM TCMs for a variety of Mazda models. Please contact us if you need help finding the right TCM for your transmission.