Blog Car Care Advice What The Transmission Light Means: 7 Reasons Why It’s On
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What The Transmission Light Means: 7 Reasons Why It’s On

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Notice a visible light flashing a thermometer and gearbox symbol on your dashboard? Or a gearbox with an exclamation mark?
That’s your transmission warning light, and you should pay attention.

A lit transmission light can be a reflection of car troubles like bad transmission, gearbox issues, or a low fluid level.

In this article, we’ll describe seven transmission problems that might turn on this light. We’ll also cover how you can fix the warning light and if you can drive with the check transmission light on.

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Let’s get started.

What Is A Transmission Warning Light?

If your check transmission light is on, it probably means something is wrong with your transmission or the gearbox

How your transmission light looks depends on your vehicle’s make and model. It’s a visible light with a distinct symbol, so you’ll be hard-pressed to miss it — a gearwheel encircling a thermometer or exclamation point is pretty common. Certain vehicles may have a simple text string alerting you of an issue, while others may not even have a transmission light. 

The check engine light may also pop on, along with the transmission warning light. An illuminated check engine light is an early indicator of transmission and other related problems. 

NOTE: Your vehicle may be forced into a fail-safe or limp mode when the transmission dashboard warning light turns on. Also, manual transmission cars don’t have a transmission warning light.

So why does a transmission light turn on?
Let’s find out. 

7 Key Causes For A Lit Transmission Warning Light

The transmission light can show up due to problems like a simple electrical malfunction, low transmission fluid level, or difficulty shifting gears. 

Here are a few other transmission problems that might trigger this warning light:

1. Transmission Overheating

Transmission overheating is the most common reason for a transmission light to come on. To prevent overheating, ensure your cooling components, like the thermostat and radiator, are working properly — and can maintain optimal transmission fluid temperature.

Here are a few reasons why your vehicles transmission could heat up:

No matter the cause, an overheated transmission should be treated like an overheated engine. You should immediately stop driving and let your transmission cool down before you get a mechanic to check it out. 

2. Low Transmission Fluid

The transmission may not work properly when your transmission fluid level is low, ultimately leading to a bad transmission and possibly severe internal damage. To prevent this, the transmission light may turn up as soon as your transmission fluid level drops.

But here’s the thing:
Transmission fluid doesn’t burn like engine oil. So if your automatic transmission fluid is low, it can indicate a transmission fluid leak. To confirm a transmission fluid leak, you can check for a dark or bright red puddle under your vehicle.

3. Internal Transmission Failure

An automatic transmission system comes with many complex internal components. 

When any of those components fail, your powertrain control module may read it as a transmission failure and turn on the transmission warning light.

4. Shift Interlock Failure

Sometimes, the transmission light may not indicate a transmission problem but can be a reflection of powertrain system failure.

Some vehicles with automatic transmissions have a shift interlock system where you need to press the brake first to shift out of ‘park.’ Your check transmission light may pop up if this system malfunctions.

5. Valve Body Problems

Most traditional automatic transmissions and continuously variable transmission systems (CVT) come with a valve body. 

Now, the valve body has many passages within them to send transmission fluid to other parts. In fact, modern valve bodies even have a transmission control module (TCM) that controls all sensors and electronics. 

This means any valve body issue can affect the functioning of the transmission system — ultimately triggering the transmission light on your dashboard.

6. Torque Converter Issues

The automatic transmission system houses the torque converter. Usually, a torque converter acts as a link between the engine and the transmission.

However, excessive use or wear and tear can cause converter issues like shuddering, slippage, or even contaminate the transmission with debris. These issues may turn the transmission light on.

7. General Maintenance Reminder 

Sometimes, a transmission warning light can also be a reminder to check fluid levels or replace bad transmission fluid. 

Automatic transmission fluid needs to be changed every 60,000 to 100,000 miles (unlike manual transmission fluid, which requires checking around 30,000 to 60,000 miles).

Regular transmission service for your vehicle will help detect the slightest problem and prevent any serious transmission trouble. 

Looking out for these tell-tale signs and accompanying signals, like an illuminated check engine light, can help you diagnose and fix the problem sooner. 

But how serious is a transmission light?

Can I Drive With A Transmission Light On?

The transmission light can show up for several reasons, some of which can be severe, like difficulty in shifting gears, low transmission fluid level, or a high fluid temperature.

So it’s best to diagnose and fix the transmission issue soon to avoid getting stranded and prevent irreversible damage.

Next, let’s check how you turn off a check transmission light.

How To Fix An Illuminated Transmission Light

Fixing a transmission warning light depends on what caused the light to come on. However, here are some ways you can fix the problem: 

1. Stop Driving

The best thing to do when a transmission light comes on is to stop driving, especially if you face gear shifting problems or a low fluid level. Ensure you get a complete check done to avoid permanent transmission damage.

 2. Scan For Trouble Codes

You can diagnose the transmission dashboard warning light with an OBD II code scanner

If there are multiple trouble codes, you can reset the code and test drive your vehicle. This will help you retrieve relevant transmission trouble codes when the transmission light comes back on. 

Here are some trouble codes you may come across:

3. Go To A Professional Mechanic

The best way to deal with an illuminated transmission warning light is to contact an expert mechanic. Luckily, AutoNation Mobile Service offers expert technicians who can help diagnose the issue. 

Why AutoNation Mobile Service?
Here’s how AutoNation Mobile Service offers excellent service:

Fill in this online form for an accurate quote for diagnosing your transmission issue. 

Final Thoughts

A transmission light can turn on for several reasons ranging from an overheating transmission and bad transmission fluid to gear change issues. Checking the transmission fluid level and getting regular transmission service can help prevent car issues.

But if a transmission light appears, simply contact AutoNation Mobile Service.