Home » blogs » car wiring harness » Service Trailer Brake System Error – Symptoms and How to Reset?

Service Trailer Brake System Error – Symptoms and How to Reset?

Service Trailer Brake System

There are numerous warning signals on your car dashboard. It gives you alerts about potential issues. The Service Trailer Brake System message is one of these errors, but what does it indicate? Well, there are many causes of triggering the trailer brake system warning.

We will discuss the major reasons behind it and know how to reset a vehicle’s service trailer brake controller.

What Does the Service Trailer Brake System Mean?

The trailer brake system is a crucial component of towing. The device is mounted on the dashboard near the driver.

Service Trailer Brake System Mean

The trailer brake controller system fits on the vehicle to assist the driver in controlling the trailer’s speed as well as stopping. It can be an OEM or aftermarket device.

When it’s time to stop, there will be a slight delay because this brake controller mechanism activates proportionally to the vehicle’s brakes. Thus, it provides more control of towing vehicle speed and ultimately helps in safe driving. Most of these systems are adjustable using the display’s plus and minus settings.

Types of Trailer Brakes

There are two types of trailer brakes:

Surge brakes

These brakes are a component of a self-contained hydraulic braking system. It relies on the trailer’s weight and momentum for proper functioning. Thus, surge brakes won’t require anything electrical to function.

However, the driver’s poor control of surge brakes is one of their main drawbacks.

Electric Brakes

These brakes will operate the electromagnetic brake drums by drawing electricity from the towing vehicle. The electric brake system is programmable and gives freedom to the driver to activate the brakes as per need.

What to Do in Case of Trailer Brake System Warning?

When the warning “service trailer brake system” appears on your dashboard, it alerts you to a problem with the trailer wiring harness or brake. It will quickly stop the flow of the power supply from the truck to the trailer.

If you see the warning light, firstly, you must unplug the brake controller to turn off the trailer brake system. The brake controller, however, cannot be unplugged if it is hardwired. In that case, cut the brake output line running between the brake controller and the trailer brakes.

Another activity that you can do is reset the trailer break. We will discuss the process at a later stage. However, you must identify the reason causing the flashing of the warning light. It helps you to prevent the problem from occurring again. We will discuss the reasons behind the service light brake system light in the next section.

Why Does the Trailer Brake System Light Keep Coming ON?

The Service trailer Brake system is an essential component. These are the major causes behind the service trailer brake controller message on your dashboard.

Poor Trailer Brake Control Button

A trailer brake controller is usually beneath the dashboard in most cars. However, the trailer brake control button may fail. The most common cause can be carbon build-up at the terminals.

If you have a Ford with the Service Trailer Brake System, you will find it more often. The best practice is to clean the terminals.

Blown Fuse

It is a major symptom of a failing trailer brake system. Every electrical part of your car runs with the assistance of a fuse. The fuse helps to prevent the excessive flow of voltage. So, whenever there is an excessive flow of power supply, the fuse will blow to prevent the electrical part. So, when there is a flashing error message on your dashboard, then the blown fuse of the trailer brake system can be the culprit. 

Defective Brake Light Button

The warning light flashes if the brake light switch malfunctions. However, it is typically inexpensive to replace this component. In most car types, the brake light switch is on the brake pedal, and changing it yourself is also easy.

Faulty Master Cylinder

A master cylinder and a few sensors are used in the brake system to make sure everything is working properly. However, when the trailer brake system warning sign flashes, along with other signals, it could be the reason. You could have to pay a higher repair fee depending on the damage.

Faulty Wiring

Another common reason for a defective trailer brake system is a faulty trailer wiring harness. It could be due to the fraying of the wire.

How to Turn OFF the Service Trailer Brake System?

Here is the quick process of resetting the service trailer brake system. However, firstly you need to assemble certain tools.


You will need the following tools:

  • Hammer.
  • Flathead screwdriver.
  • A hardwood.

Now, follow these steps to reset or turn off the trailer brake controller.

  1. Find the trailer’s Adjustment Nut

Find the location of the adjustment nut on the trailer. It is often located behind the brakes on the trailer. Normally, this nut is situated close to the axle. You can use the car manual to confirm the nut.

  1. Use a Screwdriver to Remove the Lock Nut

The lock nut on the adjustment nut fastens it to the trailer brake. For this lock nut, a flathead screwdriver is needed.

  1. Turn the Adjustment Nut

Free the adjustment nut now. Turn it in a clockwise direction. Secure it at the backing plate. Do not tighten the nut too much.

However, even after this process, the dashboard still reflects the warning sign, then take your vehicle to the mechanic.

Service Trailer Brake System – Frequently Asked Questions

How frequently should I service trailer brakes?

Generally speaking, you should service your trailer brakes once a year or after every 10,000 miles. However, if you drive for long distances, you should take it to a mechanic shop more often.

How is a trailer braking system reset?

It’s simple to reset your trailer brake controller.
➢Find the trailer’s adjusting nut first. It is often located behind the trailer brake, close to the axle.
➢After that, using the flathead screwdriver, loosen the locknut.
➢Turn the adjustment nut clockwise and secure it against the backing plate.

What does the service trailer brake system indicate in my Ford?

If you are receiving a trailer brake controller error in your Ford truck, then possibly there is a malfunction in your trailer brake controller wiring. If an error occurs, the system will cut the power supply.

Can I drive with a trailer brake system error message?

If you are driving with a trailer, you should consider the service trailer brake system alert. The brake will respond and perform as there will be no power supply. So, if you don’t solve the issue and keep driving, it can cause a major problem.

How do you adjust a Brake Controller?

The first task is to locate the brake controller. After locating it, follow these easy steps.
➢The first step is to press and hold the controller’s “set” button for two seconds.
➢Change the braking force by using the arrow keys.
➢Save your changes by pressing “set.”

Request a Quote For car wiring harness

Need Help?