Why Is The AT Oil Temp Light Flashing In My Subaru?

AT Oil Temp Subaru Warning Light

On the dashboard of your Subaru, there are various warning lights letting you know when something is wrong with your vehicle. If you’ve never seen the Subaru AT oil temp light flashing before, it can catch you off-guard. This warning light serves as a serious warning and should never be ignored.

In this guide, we cover the basics of the flashing Subaru AT oil temp light and show you what causes it. We also outline some ways to fix this Subaru malfunction and give you answers to your top questions. 

What Does A Flashing Subaru AT Oil Temp Warning Light Mean?

The AT oil temp light is used for the Automatic Transmission Oil Temperature system. A flashing light means that the automatic transmission fluid has gotten too hot compared with the manufacturer’s specifications. The light blinks because it’s a serious problem that shouldn’t be ignored.

Along with the light, you’re going to notice several symptoms. Most importantly, the transmission isn’t going to perform its duties normally. As soon as the light starts blinking, it’s important to pull over and let the transmission cool off before permanent damage occurs. 

What Causes A Subaru AT Oil Temp Light?

If you see an AT Oil Temp light on your Subaru’s dashboard, you may have pushed your Subaru too hard. It could also be caused by low transmission fluid, the wrong type of fluid, or a bad transmission fluid temperature sensor. Other options include defective wiring, a slipping transmission or a bad transmission oil pump. 

Any one of these causes is serious and should be remedied before driving any further. 

1. Overheating Transmission (Hard Driving)

cars driving steep hill

Subaru vehicles are meant for some extreme adventures. However, there’s always a chance that you’ve pushed your vehicle too hard.

If you are towing heavy loads, climbing steep inclines or tearing up the trail, you may have overworked the transmission. Thankfully, if you stop immediately and let the transmission cool off, you may not have any repairs to make. 

2. Low Transmission Fluid Level

check transmission fluid level

When you run the Subaru with low transmission fluid, it can cause serious consequences to your vehicle. First, it’s going to overheat the transmission because of the lack of lubrication.

In normal driving situations, the Subaru shouldn’t have low fluid. If it does, you may consider that the system is leaking somewhere. To prevent this problem from occurring again, you need to not only fill the transmission back up but also fix the leak that’s causing the low fluid. 

RELATED: 6 Signs Of Low Transmission Fluid And How To Check the Level

3. Wrong Transmission Fluid Used

transmission fluid

There are different types of transmission fluid available. It’s important that you put the right type in your vehicle or it could lead to problems. 

For most vehicles, Subaru recommends using Subaru ATF HP or Dexron III in the transmission. Using the wrong one for your vehicle can lead to serious consequences, possibly even transmission failure. It can also cause the AT oil temp to start flashing. 

4. Bad Transmission Fluid Temperature Sensor

If the sensor designed to check the fluid temperature fails, the readings will be inaccurate. The first sign will be a flashing light, indicating that something is wrong with the system.

You may also notice the transmission not shifting as it normally would because adjustments aren’t being made properly. In severe cases, the car can go into limp mode to protect the transmission. 

5. Bad Wirings

damaged car wirings

The transmission is a mechanical part, but it’s made up of many electrical connections. Between every sensor and the transmission is an electrical connection that needs to be in good working order to communicate.

If some of the wiring or a connector fails or breaks, it can cause communication to cease. What you’ll get in return is a flashing AT oil temperature light. 

6. Slipping Transmission

Normally, a slipping transmission is a sign of a larger problem. The transmission could be slipping because of a failing clutch pack.

It’s also possible that there are hydraulic circuit problems. Furthermore, any of the issues we’ve already discussed could lead to a slipping transmission too. Whatever the cause, when the transmission starts to slip, the oil can heat up and cause this warning light to blink. 

7. Bad Transmission Oil Pump

The transmission oil pump is responsible for circulating the fluid in the transmission. When it fails, the transmission won’t get the lubrication it needs and it will overheat.

You may start to hear a whining noise or experience slipping. Once the pump fails completely, you may not be able to get the transmission into any gear. 

How To Fix A Subaru AT Oil Temp Warning Light

Once the AT oil temperature warning light starts to blink on your dashboard, you want to take quick action to resolve the problem. Ignoring it could lead to complete transmission failure. As professional mechanics, these are the steps we would take. However, we always recommend reading your service manual for model-specific information. 

1. Check the Transmission Fluid Level

transmission fluid level

Before you do anything else, make sure there’s enough fluid in the transmission. Warm up the engine first and make sure you are parked on a level surface.

Take out the transmission fluid dipstick and wipe it off. Replace it back in the system and pull it back out. Make sure the fluid level is between the fill and full marks. If more is needed, add it until it reaches the appropriate line. 

RELATED: How to Check Automatic Transmission Fluid

2. Change and Flush Transmission Fluid

If the transmission fluid looks burnt or old, you should consider changing or flushing it. A transmission fluid change is similar to an oil change.

On average, Subaru recommends changing the transmission fluid every 30,000 to 60,000 miles. However, if you push your vehicle to the limits, it may need to be done more frequently. 

3. Read Trouble Codes From the Transmission Control Module

read trouble codes

The transmission control module is responsible for communicating with the engine for a seamless ride. However, when the module senses something is wrong with the system, it will throw an error code.

You may be able to read the trouble code with your scanner. However, not all scanners are designed to work with the TCM, so you may need to upgrade. Once you get the information from the module, reference it with our online trouble code library to figure out what’s wrong. 

4. Check Sensor And Wiring

Your next step is to inspect the sensor and the wiring. There’s always a chance that something has gotten disconnected or is bad.

Trace all of the wiring and make sure you look at the connectors as well. Replace anything that’s damaged. 

5. Update TCM

Subaru has issued a service bulletin revealing that the P0841 trouble code may indicate a problem with the Transmission Control Module. This problem seems to be most prevalent with select 2018 Subaru models. 

To fix it, the dealer can update the TCM with new logic. The update allows the solenoid to get rid of contamination better, so the alert stops occurring. 

6. Contact A Professional

It isn’t always simple trying to diagnose and repair a problem with the transmission. Because of the importance of the transmission, we don’t recommend working on this part unless you have adequate experience.

You don’t want to cause more damage, which is why it’s sometimes better to pay a mechanic instead. If you aren’t sure what’s wrong, err on the side of caution and get a second opinion. 

Why is my Subaru flashing AT oil temp?

You may have overheated the transmission from pushing it hard. The fluid could be low, or you might have used the wrong type. Additionally, the transmission fluid temperature sensor could be bad, there may be defective wiring, the transmission could be slipping or the oil pump might have failed.

How long can you drive with the oil temperature light on?

You shouldn’t continue driving at all with the oil temperature light on. It’s important to pull over right away in a safe location. You want the transmission to cool completely down before attempting to drive again. If it continues happening, figure out what’s wrong so you can fix it. 

What causes the transmission to overheat?

Sometimes, it’s just that you’ve pushed it too hard. It could also mean that the fluid is low or contaminated. Mechanical failures are also a possibility if the wiring, fluid temperature sensor or oil pump is bad. Furthermore, a slipping transmission can cause it to overheat. 

How do I cool down my transmission?

The best way is to pull over into a safe location and turn off the car. You can pop the hood and wait for the transmission to cool down. This may take a half an hour or more, depending on hot the transmission got and what the temperature outside is.  

How much does it cost to replace the transmission fluid temperature sensor?

You may spend $250 to $550 to have the transmission fluid temperature sensor replaced. The parts could cost $125 to $175, while the labor may add up to between $125 and $500. The total cost depends on your vehicle type and where you live.

There are some things you should never mess around with when it comes to your car. The flashing AT oil temp light on your vehicle is one of them. This is one sign that you should pull over immediately and take stock of what’s going on.

If you continue driving, you are going to create permanent transmission damage. If you’ve ever priced out a new transmission, you know how expensive it will be if you cause any more wear.


Categories: Warning Lights

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