Service Trailer Brake System Warning Light: Meaning, Causes, and Reset

The service trailer brake system warning light on your vehicle’s dashboard indicates a problem with the trailer brake controller system. This system is responsible for regulating the speed and stopping of a trailer that is being towed by the vehicle. In this article, we will discuss the meaning of the service trailer brake system warning light, the causes of the error message, and how to reset the system.

What is a Trailer Brake Controller System?

A trailer brake controller system is an OEM or aftermarket module that is installed in a vehicle to help the driver regulate the speed and stopping of a trailer that is being towed. The system engages in direct proportion to the vehicle’s brake or at a time-delayed frequency when reducing speed to stop. Most trailer brake controller systems are fitted with a plus/minus adjustment gain.

What Does the Service Trailer Brake System Warning Light Mean?

The service trailer brake system warning light indicates that there is a problem with the trailer brake controller system. The error message is a warning signal that reveals a disengagement of a trailer from the towing vehicle, such that it can no longer receive power from the vehicle to function. When this occurs, it will manifest a couple of other symptoms besides the error message. Some of the signs include a delay in the process of stopping the trailer, a sharp noise from the brake, a sinking pedal, and a sudden unresponsive or mushy feeling when you engage the trailer brake.

Causes of the Service Trailer Brake System Warning Light

The service trailer brake system warning light can be caused by a problem with the trailer brake wiring or the module that hinders the power supply from the tow truck to the trailer. The problem may also be due to faulty ITBC (integrated trailer brake controller) wiring or module.

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How to Reset the Service Trailer Brake System Error Message?

Resetting the service trailer brake system error message is not a big deal. The process requires a couple of tools, including a flathead screwdriver, a piece of solid wood or rock, a strong hammer, and probably an assistant to help make the work easy for you. Once you have these tools available, you can proceed to commence the reset process immediately.

Step 1: Identify the adjustment nut on the trailer
The first step is to find the adjustment nut, which is right at the back of the vehicle’s trailer brake. It is usually situated close to the axle.

Step 2: Loosen the locknut with a screwdriver
There’s a locknut that is used to secure the adjustment nut on the trailer brake. Now, get the flathead screwdriver and use it to loosen this nut.

Step 3: Turn the adjustment nut clockwise
Once you finally loosen the locknut and the adjustment nut is finally free, turn the adjustment nut clockwise carefully until it snugs against the component’s backing plate. However, while adjusting the nut, make sure you don’t overtighten it to avoid complications.

If the recommendation above does not rectify the problem, you most likely have a bad trailer brake system. You may have to get a new replacement for the component.

Is It Safe to Drive With Service Trailer Brake System Error?

While it is possible to drive a vehicle with the service trailer brake error message, it is not safe or ideal to do so. Safety must be 100% at all times. So, the fact that a vehicle moves irrespective of a fault does not mean all is well. A slight error can cause severe damage or an accident when you least expect it. Therefore, it is best to fix any fault you spot in your vehicle until you are sure that the problem is no more.

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