Transmission Warning Lamp - Common Causes & Fixes

The Check Engine Light is probably the most well-known of all the indicators on your dashboard. However, one light is lesser-known, the transmission warning light or transmission symbol, but it’s not any less important. What is the meaning of the transmission warning light and why does it come on?

If you see the alert for your transmission, it’s time to take action. For a smoother ride, we explain what the alert means and give you some tips on how to correct it. You can also find out if you should stop driving despite the alert appearing on your dashboard. 

Índice de Contenido
  1. What does the Transmission Warning Light mean?
  2. How to fix the transmission warning light
    1. 1. Don't Drive
    2. 2. Check Trouble Codes
    3. 3. Seek out a qualified mechanic
  3. Transmission Warning Light Causes
    1. 1. Low Transmission Fluid
    2. 2. Overheating Transmission
    3. 3. Failure to Shift the Interlock
    4. 4. Malfunctioning Valve Body
    5. 5. Conversion of Faulty Torque
    6. 6. Internal Transmission Failure
    7. 7. Computer/Electrical Malfunction
  4. Do I need to turn the transmission warning light on?

What does the Transmission Warning Light mean?

If the transmission warning lamp is illuminated, this indicates an issue in the gearbox or transmission. Transmission warning lights are not always present in every car. It could appear differently depending on what make and model of car you have.

The thermometer could be wrapped around a gear symbol, or it might contain a text string warning you of the problem.

You can find details on your particular model in the owner’s manual. If an alert appears on your dashboard relating to transmissions, this means that there is a problem that needs to be addressed immediately. 

RELATED: 90 Car Dashboard Symbols, Warning Lights & Indicators – Meanings

How to fix the transmission warning light

1. Don't Drive

The transmission warning light should be watched just as you are paying attention to the Check Engine Light. When the light comes on, it’s always best to stop driving and get a better feel for what’s happening before continuing.

Even if you don’t notice any signs of something wrong, you want to perform a complete inspection. You could end up with permanent transmission damage. If the transmission is not lubricated and you drive on, it may be necessary to replace the entire transmission. Instead of changing the fluid, it is possible to just add some. 

2. Check Trouble Codes

You can view the alerts in your OBD-II compatible code scanner. Plug your code scanner into the OBD-II port and read the DTCs to see what’s going on.

If there are too many codes to navigate through, it’s best to reset the light and take the car for a test drive. The light will turn on again after a while, so you can retrieve the codes that are relevant to your problem.

3. Seek out a qualified mechanic

If the codes don’t provide you with the information you need to repair the problem, it’s best to talk to a mechanic. It is important to be prepared for any other unusual circumstances that may arise when you contact a mechanic.

In some cases, it’s best to visit a shop that deals specifically with the transmission. This would be ideal if you are concerned that there’s a major issue that might require a transmission rebuild or replacement. 

Transmission Warning Light Causes

1. Low Transmission Fluid

To prevent any damage, an alert could go off when the transmission fluid falls below the recommended level. The transmission may not function normally if the fluid levels drop too low. 

Your car shouldn’t be burning through transmission fluid as it might oil. Any drop of transmission fluid must be drained immediately. 

Related: Low transmission fluid symptoms (check the level)

2. Overheating Transmission

Whether the fluid is low or there’s failure occurring internally with the transmission, if this vital component starts to overheat, the alert will come on. A blocked cooler may be the cause of an overheating transmission in some instances.

If you carry heavy loads, the transmission may also heat up. The transmission should be treated as an overheated engine. You should stop driving as soon as the transmission cools. 

READ MORE: What's the normal operating temperature of an automatic transmission?

3. Failure to Shift the Interlock

The transmission warning light may not necessarily indicate failure of the component. This could indicate that the powertrain or another component is malfunctioning.

BMW vehicles have a shift interlock that prevents you shifting from Park to Normal unless the pedal is pressed first. The transmission warning light may come on if this system fails. 

RELATED: Car Won’t Shift Out of Park (Causes & What to Do)

4. Malfunctioning Valve Body

A valve body is part of the automatic transmissions and CVTs. This vital part contains valves that are responsible for directing flow through the passages, so it gets delivered to the transmission when it’s needed.

In today’s valve body, there will also be a transmission control module (TCM) that operates all of the sensors and electronics. The transmission warning light may come on if any part of the valve body fails. 

READ MORE: 6 Symptoms of a Bad Valve Body (& Replacement Cost)

5. Conversion of Faulty Torque

An automatic transmission includes a torque converter. The torque converter is a part that links the engine and the transmission.

Torque converters can become worn out from excessive wear or old age. Gear slippage and shaking can result. You may experience transmission contamination due to the possibility of it separating. A failing torque converter will indicate that the transmission is in danger. 

6. Internal Transmission Failure

With so many internal parts working to keep the transmission running, it’s possible for just about anything to fail. You will also find clutch packs, gears, and many other internal parts within the transmission. 

With any internal failure, the transmission won’t be able to run as intended. The transmission warning light will turn on when this happens. 

7. Computer/Electrical Malfunction

Modern transmissions are controlled by high-tech electrical connections and sensors. The transmission control module ensures that all sensors work accurately and efficiently. Any of the sensors and electrical connectors can go out at any given time.

If there’s even the smallest glitch in the system, the transmission might not be able to run properly. A defective solenoid, failing computers, or damaged wiring can cause the warning light to turn on. 

Related: 6 Signs that a Transmission Control Module (TCM), is Bad

Do I need to turn the transmission warning light on?

We’ve previously discussed this, but it’s important to reiterate that you shouldn’t drive with the transmission warning light illuminated. Your car’s transmission is expensive, one of the most valuable parts of the vehicle. For this reason, you don’t want to mess around with any faults that could lead to permanent damage. 

You might stop driving when you realize there is a very minor problem, like a leak. If this is the case, fill up your system with fluid and drive on while you monitor the situation. However, if the transmission is overheating or there is an internal failure, you don’t want to procrastinate in any way. You could also let the leak go for a while, but it can quickly escalate into a bigger problem.

For these reasons, it’s best to have the problems resolved immediately. The fault should be fixed immediately to prevent future transmission issues. You could find yourself stuck on the sidelines, away from your mechanic, if you don't fix the problem quickly. The transmission repair cost could be anywhere between $1,500 and $3,500.

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