How to Fix the AT Light on Mazda 6? Reasons and Best Solutions

Mazda 6 is a great sedan. Owning one should fill you with pride and a great sense of achievement. While driving your car, you may have noticed the bold orange letters 'AT' on the instrument cluster. Seeing these warning lights will alarm you, especially if there are other accompanying signs.

AT light highlights

• Common reasons:issues with automatic transmission's electronics
• How to fix:take the car in for inspection
• Possible consequences:AT failure is possible but not inevitable
• Priority level:High
• Can you drive?Carefully
• DIY repair:Impossible
• Repair price range:$250-$4,000

The AT warning light on Mazda 6

The letters AT stand for Automatic Transaxle, which is related to the car's transmission system. The AT light should not be confused with the 'AT Check' light, which also pops up when the transmission has issues. According to the user manual from the manufacturer, the AT light illuminates when an electrical issue relating to the transmission occurs. On the other hand, the AT Check comes on when the transmission system, in general, encounters an issue. These issues will more likely be mechanical than electrical.

The automatic transaxle in your Mazda 6 changes the engine's torque and speed in accordance with the speed and torque requirement of the wheels. This process ensures the engine's power is matched as close as possible to the ever-changing road speeds, conditions, and loads. The transaxle input shaft connects to the torque converter, which helps interrupt and multiply the flow of engine torque into the transmission.

When the AT warning light appears on your dash, you are likely to encounter or experience some other symptoms. These symptoms, together with the warning light, will help you diagnose the problem and even have an easy time pinpointing the source of the problem. Let us now take a look at the reasons why the AT warning light appears on your dash.

What causes AT light in Mazda 6?

The best way to know what causes the AT light to appear on the dash is by checking with the OBD II scanner. The scanner will read codes thrown by the TCM, which helps you run a more accurate diagnostic test.

Some Mazda 6 drivers have reported seeing this warning light, and after restarting the engine, the light went away. For many drivers, the light never reappears. But for those that the warning light comes back, it is time to use the OBD II scanner.

Some of the causes of this light appearing however are as follows:

1) Low transmission oil

The most probable reason for the AT warning light popping up is low transmission oil in your car. Mazda 6 showcases a SKYACTIV engine, and according to Mazda, the transmission fluid used should last a lifetime. However, this doesn't mean the fluid can't get low over time. Once the transmission fluid runs low in your Mazda 6, the engine will sound different when going uphill, and the RPMs will be extraordinarily high at all speeds.

Before your car comes to a complete stall and cost you hundreds or thousands of dollars, the AT using its transmission fluid reading sensors, will alert you using the AT warning light. The AT warning light lets you know there is a potential transmission problem in advance, and if you attend to it early, you might save yourself from incurring monumental repair or replacement of parts costs.

Solution

The best answer to this problem is to top up the low-running transmission fluid. During regular service or every other morning before you head out for the office, pop up the hood and check the fluid's level using the easily accessible dipstick. If a part of the transmission is replaced, you must also change the fluid. While changing or adding the transmission fluid, check whether there is a leakage that could be causing it to run low.

2) Faulty sensor

Modern cars are equipped with countless sensors to help manage and run the car. The transaxle is connected to sensors that communicate with the TCM, which then enables the smooth running of the car. A faulty sensor will make the AT warning light illuminate. A faulty sensor can also send the wrong message to the TCM, which will then send the wrong code. Everything could be alright, but the TCM will be reading a problem with the transaxle.

Solution

As stated earlier, the easiest answer to this problem is to get an OBD II scanner and run the transmission system. But before you jump into connecting the TCM to the scanner, you should restart the engine and see whether the warning light goes away.

Many Mazda 6 owners who have encountered the AT light say it disappeared after restarting the engine. Where the restarting of the car doesn't help, it is time to replace the affected sensors. Some of the sensors to check include the input speed shaft sensor, the output speed shaft sensor, and the speed sensors.

3) A faulty TCM

The transmission control module, or TCM, as popularly referred to, is where all the readings regarding the transmission and transaxle go through. The TCM contains sensors and monitors, ensuring the transmission system runs according to manufacturer specs. If the module is faulty, you may have trouble with your transmission, and the AT light will pop up.

According to some Mazda 6 owners, their cars would jerk, and the gears would even start slipping. In other cases, the car would flash the AT light and not start even after jumping it. The car will not shift upward into 4th gear for others, and the RPMs are quite high.

Solution

According to many car owners who experienced the above problems, a change of transmission fluid helped but not entirely. The answer was found in replacing the TCM, after which the car will run smoothly, and there won't be any more gear slips and car jerking.

4) Contaminated transmission fluid and bad filter

Even though the Mazda 6 manual will say SKYACTIV and the transmission fluid will last the entire life of the vehicle, there are times when you will need to change the fluid. As stated earlier, whenever you replace a major transmission component, you will need to change the transmission fluid. Some drivers have reported noticing the AT light, and their mechanics diagnosed the problem to be a clogged transmission fluid filter and or contaminated fluid.

Solution

The solution to the AT light may cost you less than $20 by replacing the filter and the transmission fluid. Before you incur a huge bill on dismantling the transmission, you should check whether the problem is caused by a faulty filter and dirty fluid, which could be making trouble for the TCM.

The symptoms associated with AT light in Mazda 6

In many instances, the AT warning will appear alone. In other cases, the light will appear alongside CEL -check engine light. There will be accompanying symptoms that can help you diagnose and solve the problem. They include;

• CEL - as stated earlier, the check engine light is common whenever the AT light pops up.
• Gear slipping - Many owners of the Mazda 6 report noticing serious gear slipping.
• Jerking - The car will have a rough gear change, and it will jerk or shake.
• Noises - the noises you might hear may vary from car to car. However, in most cases, you will hear a grinding noise that can indicate intense friction between moving transmission components. Other times you may hear a humming or whining noise. A bumpy sound when the car is in neutral is also a symptom to listen for. This may also be accompanied by a burning smell.
• Hesitation in gear shifting - Whether going downshifting or upshifting, you may notice a slight hesitation in the transmission.

Conclusion

Mazda 6 is one of the popular cars from Mazda, offering luxury and practicality for the owner. However, the AT warning light can be a nightmare and make owning the car a real headache.

The AT light might seem like a minor issue when there are no other symptoms, but as discussed above, it can be the perfect warning you need to help you avoid repair bills amounting to thousands of dollars. It is a warning light you need to watch out for. Ensure your vehicle goes for scheduled servicing.