7 Causes of Transmission Warning Light Illumination & How to Fix It

The transmission system is one of the major parts of the vehicle. The automatic transmission is usually equipped with numerous sensors, allowing the vehicle’s main computer to precisely monitor aspects such as transmission fluid, fluid temperature, and pressure within the transmission. When there is something wrong with the transmission, a transmission warning light starts to illuminate.

As automatic transmissions can be costly to replace, it is worthwhile to maintain them properly. Many drivers are familiar with the check engine light; however, they may not be known that the latest vehicle models also feature a transmission light. This light serves to alert drivers to potential issues with the transmission. This article describes the transmission warning light illumination causes and how to reset it.

What does the Transmission Warning Light Mean?

The vehicle’s computer triggers the transmission warning light when it monitors a problem with the transmission or gearbox. This light is not installed in all vehicle models.

Transmission Warning Light

The appearance of the transmission light varies based on the vehicle model. It typically features a distinct symbol, such as an exclamation point or a gearwheel surrounding a thermometer, making it difficult to overlook. Some vehicle models may display a simple text message to inform the driver about the problem, while others don’t contain a transmission light at all.

In certain vehicle models, the transmission warning light is activated when the transmission appears to be overheating, or something is wrong with the traction control light or overdrive. For others, it serves as a general indicator for a variety of transmission issues.

It’s important to note that, in some vehicles, the transmission warning light doesn’t always signify an issue; it could also be a reminder for maintenance. For example, it may indicate low transmission fluid levels.

Causes of the Transmission Warning Light

Your vehicle’s transmission warning light comes on because of one or more of the below-given reasons:

  • Low Transmission Fluid
  • Overheating Transmission
  • Shift Interlock Failure
  • Faulty Valve Body
  • Bad Torque Converter
  • Internal Transmission Issues
  • Electrical/Computer Malfunction

1) Low Transmission Fluid

Insufficient transmission fluid is one of the major causes of the transmission warning light illumination.

When the transmission fluid level drops, the transmission will be unable to function correctly, potentially leading to a faulty transmission and severe internal damage. To warn you of this situation, the automatic transmission warning light may illuminate when the transmission fluid level decreases.

Transmission Fluid Leak

Unlike engine oil, transmission fluid does not burn off. Consequently, if you have insufficient automatic transmission fluid, it could signal a fluid leak. To verify a leak, look for a bright red or dark puddle beneath the car.

2) Overheating Transmission

Transmission overheating is one of the major reasons for the transmission warning light illumination.

Overheating Transmission

Overheating can result from various factors, including a blocked transmission cooler or internal transmission issues. Additionally, driving habits such as towing excessively heavy loads may lead to an overheated transmission.

3) Shift Interlock Failure

It’s important to note that the transmission light does not continuously indicate an issue with the transmission itself. For instance, on a few BMW models, the light may turn on when there is a problem with the shift interlock system.

Shift Interlock

The shift interlock system is a safety feature that doesn’t allow to shift of the gear selector out of “park” without pressing the brake pedal.

4) Faulty Valve Body

Automatic transmissions and CVTs of your car consist of a valve body, an essential component containing valves that direct transmission fluid flow through lines and deliver it to the transmission according to the requirements.

Modern valve bodies also include a transmission control module (TCM) responsible for managing the electronics and the transmission sensors. If any part of your valve body fails, the TCM triggers the transmission warning light.

5) Bad Torque Converter

A majority of automatic transmissions utilize a torque converter, which serves as a fluid delivery connection unit between the transmission and engine. The converter contains a lockup clutch that creates a mechanical link between your vehicle’s transmission and engine under specific conditions.

Torque Converter

Your torque converter may start to produce different issues, like slippage and shuddering. In a few cases, a faulty converter may even disintegrate and pollute the transmission with contaminants. Such problems can force the transmission warning light to illuminate.

Read More: Bad Torque Converter Symptoms and Causes

6) Internal Transmission Issues

Transmission Issues

The transmission of your vehicle contains numerous internal components, such as clutch packs, gear sets, and more, all working together to ensure smooth operation. If any of these parts fail, your transmission will be unable to work efficiently, leading to the illumination of the automatic transmission warning light.

7) Electrical/Computer Malfunction

The latest transmission models rely on a variety of electrical connections and high-technology sensors managed by the TCM for accurate and efficient operation. However, these sensors and connectors may go bad fail over time.

Even a small malfunction within the system may affect the performance of your transmission. Consequently, a faulty solenoid, a malfunctioning TCM, or damaged wiring may all trigger the transmission warning light.

Read More: Signs of Bad Starter

How to Fix the Transmission Warning Light

To fix the transmission warning light, follow the below-given steps:

  • Stop Driving
  • Scan Trouble Codes
  • Contact a Mechanic

1) Stop Driving

Similar to the Check Engine Light, it’s crucial to fix the transmission warning light. If this light illuminates, it’s recommended to stop driving and assess the situation before proceeding.

Even if there are no apparent signs of an issue, it’s essential to ensure a thorough inspection to avoid permanent transmission damage. For instance, continuing to drive with insufficient fluid could lead to the need for a complete transmission replacement. In contrast, adding fluid might have resolved the issue.

2) Scan Trouble Codes

Using a compatible OBD2 code scanner, you can find the issues within the system. Connect the scanner to your system and read the Diagnostic Trouble Codes (DTCs) to determine the problem.

If there are multiple trouble codes, you may consider resetting the light and performing a test drive. After a few minutes, the transmission warning light must reappear, enabling you to save only the codes related to the current issue.

3) Contact a Mechanic

If the codes do not offer sufficient data to resolve the issue, it’s advisable to consult a professional. When making the call, be prepared to describe any unusual occurrences and provide the trouble codes.

In some situations, visiting a specialized transmission shop may be the best option, particularly if you suspect a significant problem that could necessitate a transmission replacement or repair.

FAQ Section

What does the automatic gearbox warning light mean?

The automatic transmission warning light also called the gearbox warning light, indicates an issue with your transmission that may be caused by insufficient fluid level, higher fluid temperature, or pressure issue.

Can I drive with an illuminated transmission warning light?

Yes, you can drive with the illuminated transmission warning light, but it is not recommended. This warning light may illuminate because of various causes, some of which could indicate serious issues. The transmission is a most valuable component of your car, and as such, you shouldn’t ignore any potential issues that may result in its permanent damage.

How to reset transmission warning light?

  • Check the transmission fluid and add more fluid if needed
  • Replace the faulty shift interlock
  • Replace the bad valve body
  • Replace the faulty torque converter
  • Fix the issues related to the transmission
  • Fix or repair the damaged wiring
  • Repair the computer malfunction

Can I drive with a bad automatic transmission?

It is not advisable to drive with a faulty automatic transmission, as it may cause further damage, poor vehicle performance, and unsafe driving conditions. It is recommended to properly diagnose and fix the issue as soon as possible.

How to prevent transmission warning light from triggering?

  • Regularly check your transmission fluid and ensure a sufficient fluid level.
  • Regularly service your cooling system
  • Ensure proper maintenance of your transmission according to the manufacturer’s recommendations.
  • Avoid using the wrong transmission fluid
  • Avoid towing
  • Avoid aggressive driving
  • Prevent transmission from overheating
  • Warm up the vehicle before driving

What are the signs of a bad Transmission?

  • Refusal to switch gears
  • Transmission warning light
  • Burning smell
  • Leaking fluid
  • Noises when in neutral
  • Slipping gears
  • Grinding or shaking
  • Dragging clutch

Can transmission light illuminate due to low transmission fluid?

Yes, the low transmission fluid is one of the major causes of transmission light illumination. When the transmission fluid level drops, the transmission will be unable to function correctly, potentially leading to a faulty transmission and severe internal damage.

Will a warning light come on for transmission problems?

Yes, when there is something wrong with your transmission, check engine light or a transmission light starts to illuminate on the vehicle dashboard.

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