Automatic Transmission Warning Light. How To Troubleshoot?


Multiple sensors in modern automatic gearboxes allow the computer to readily and precisely regulate things such as fluid level, fluid temperature, and overall transmission pressure. Because automatic gearboxes are incredibly costly to replace, it’s prudent you keep them in good working order.

The automatic transmission warning light or gearbox warning light indicates a problem with the transmission, which might be caused by a problem with the fluid level, fluid temperature, or pressure.

This article will help you understand what an automatic transmission warning light is, how it looks, and possible reasons for it to come on. I’ll also discuss what can be done to minimize the damage before taking the vehicle to the mechanic.

Meaning of Automatic Transmission Warning Light

In case the computer finds any erroneous sensor readings, a code is saved, and the automatic transmission indicator light flashes to warn the driver of potential problems. 

Sensors that aren’t working correctly can produce misleading readings, causing the light to turn on, so get them checked often. The transmission fluid temperature being greater than usual is one of the most prevalent concerns that leads this indicator light to glow.

What a Transmission Light Looks Like?

A transmission warning light isn’t present in all automobiles. However, the appearance of the light will vary depending on the car’s year, make, and model.

Some automobiles will flash the overdrive light or show an entire message in the driver’s information center to indicate a transmission problem. Some will have a symbol that looks like a gear with an exclamation mark or show a thermometer (for temperature transfer).

It’s strongly advised that you examine your owner’s handbook if a warning light displays on your car’s dashboard to figure out what the light could imply.

Read: Automatic Transmission Have Grinding Noise When Put in Gear. How To Fix?

Reasons Automatic Transmission Warning Light Turns On

There are several reasons for transmission failure, thus causing the warning light to turn on.

General Maintenance Reminder 

It’s just a basic maintenance alert to let you know when it’s necessary to check or replace your transmission fluid. In case it’s low, the very first thing you should do is take your car to a mechanic to have the fluid levels checked to determine whether you need a refill.

Temperature Level

According to specialists, heat is the leading cause of transmission failure. It’s responsible for over 90% of all automatic transmission failures, particularly in the United States. As a result, ensure you have enough transmission fluid and your cooling devices function. If your engine’s temperature lights turn on, or you can smell that something is burning, immediately check.

Read: Why Does An Automatic Transmission Have High RPM Before Shifting?

Internal Transmission Failed

Automatic transmissions are complex assemblies with many internal parts such as planetary gear sets, turbine, torque converter, etc. And whenever one of those parts break down, the car system may notice an unwonted vehicle function and this may trigger the transmission warning light to flash.

Shift Interlock Problems

The transmission warning light may not exclusively specify that the transmission has a problem. The warning light may activate on some BMWs because of the shift interlock system—a mechanism that forbids the driver from pulling the gear selector out from “park” without pressing the brake pedal—is out of order.

Issues With the Vehicle’s Valve Body

A valve body in a vehicle is located in the majority of continuously variable transmissions (CVTs) and traditional automatic gearboxes. Several channels in the valve body regulate fluid flow via valves to different portions of the gearbox. 

The transmission control module (TCM) and related electronics are frequently used in contemporary valve bodies. An issue with the valve body might be the reason for the transmission to not perform properly, leading to the transmission lights to glow.

Read: What Does a Slipping Transmission Feel Like?

Problems With Torque Converters

Torque converters can be found in many automatic gearbox systems. The torque converter serves as a fluid coupling mechanism between the transmission and the engine. 

Under some circumstances, a connection is initiated between the engine and the transmission by the clutch in the converter. This torque converter may face certain issues over time, such as friction and shaking. A malfunctioning converter can even fall apart and infect the transmission with trash in such instances. This issue may result in transmission warning lights to flash.

Computer and Electronics Control Issues

Like almost every other parts of a modern automobile, the gearbox is regulated by a control module where data is transfered via various sensors. This module interacts with other modules, via a network of data.

Any fault generating in this module, sensor, and the data network may result in the transmission warning lights being on. Other electrical problems, such as faulty wiring or a defective shift solenoid also might lead to the transmission warning sign to glow.

Read: Why Automatic Transmission Slipping When Accelerating?

Getting Caught Out of Gear and That Shrieking Noise

You can bet your bottom dollar that if your car starts slipping out of gear on occasion, it’s an indication that your gearbox is broken.

Also, when you’re driving or shifting gear, a high screeching sound emanating from the engine area typically indicates a transmission problem. It might just be a lack of fluid or a clogged filter. However, the transmission may be on the verge of failing.

Driving With the Automatic Transmission Warning Light On

Although you may not feel any difference while driving with the light turned on, you must get it examined as soon as possible to avoid any more damage. Long durations of driving with this warning light on are likely to inflict a lot of harm to the gearbox, lowering its lifespan dramatically. 

Some automobiles may enter a mode referred to as “limp home.” This mode reduces transmission stress by curbing the vehicle’s peak speed.

In addition to that, the body (or chassis), the engine, and the gearbox are the three most costly elements of a car. And the fact is that new engines and gearboxes might be more expensive and provide less performance. As a result, these high-end items don’t necessarily offer the highest fuel mileage.

Read: Oil Light in Car: What To Do and How To Fix?

Troubleshooting Ideas for Transmission Warning Light

As your transmission light turns on, the smartest thing to do is pull over to the side of the road as fast as possible. This warning light indicates that your transmission is now in jeopardy. 

As soon as you’re able to, find a safe location to pull over and park the car until your transmission has had time to cool down. After your gearbox has cooled down, you can try to restart the vehicle and resume driving, but do so cautiously. At this time, the only thing on your mind should be getting to a technician. 

If the light turns back on, turn the ignition off again and wait for it to cool. If it persists and You are too far from a mechanic, consider getting the vehicle towed.

Also, investing in your OBD2 scanner is one way to quickly narrow down why the check engine light turned on without having to visit a repair shop. A mechanic would use onboard diagnostic equipment to examine the indicator lights that appear on your dashboard. 

When you connect one into your car, it can tell you what the problem is that triggered the light to turn on in the first place. This is incredibly useful when checking an engine light since it may take you to the particular portion of your car producing a problem; in this case, it’s your gearbox.

Your mechanic may cost several hundred dollars, but you can easily find an OBD2 scanner like Autel AutoLink OBD2 Scanner (available on Amazon) at an affordable price. This great quality scanner is compatible with 7 languages and several makes and models to help you understand what’s wrong with your car. 

A scanner doesn’t resolve the fault, but it tells you if the trouble is with the gearbox, alternator, catalytic converter, or other components in your car. That way, you will be better positioned to know how fast you need to go to the mechanic to get this problem fixed. And if it’s your transmission, you’ll want to get it checked out as quickly as possible.

Read: Why Automatic Transmission Slipping When Hot?


In case your transmission begins to fail, you won’t have much time to respond. If your transmission light turns on, it’s not something you can put off until the weekend or whenever you have the opportunity to deal with it. 

If you do, there are strong chances that you might damage your vehicle so badly that it might cost you an arm and a leg; you never want to take that risk. So as soon as your transmission light goes on, please get professional help.

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