Service Trailer Brake System – Meaning and Causes

Do you get a service trailer brake system warning message on your car's dashboard? Here's what it means, what causes it, and some tips on how to fix it.

Trailer Brake System

Your vehicle’s dashboard contains many different warning messages that alert you to potential problems. One such error you might see is the Service Trailer Brake System message, but what does it mean and how can you fix it?

In this article, we take a closer look at this trailer brake warning. We also give you a few suggestions that will help you remove the warning from your dashboard. 

What Does the Service Trailer Brake System Message Mean?

The Service Trailer Brake System message tells us that there’s been a disengagement of the trailer brake system because of wiring or other malfunction. The trailer being towed may not have an adequate power supply, thereby, the brake system is hindered.

Aside from the warning, there could be other symptoms. You may notice trouble stopping the trailer because of the malfunction. There could also be strange noises when you brake. Without the right amount of power, there could also be trouble with the lights and electronic equipment on the trailer. 

What are Trailer Brakes?

The trailer brake controller can be OEM or aftermarket, depending on when it is installed. This device gets installed on the vehicle that’s towing to give the driver more control over the speed of the tow trailer or vehicle. This device gets mounted directly to the dashboard near the driver, where it’s easy to access.

This brake controller system engages in proportion to the vehicle’s braking, allowing for a small delay when it comes time to stop. You can adjust most of these systems with the plus and minus settings on the display. 

You can fit a brake system to the trailer with many different types. It’s easy to use a system with enclosed trailers, camper trailers, horse trailers and boat trailers. 

Causes of Service Trailer Brake System Message

The most common reason you might see a service trailer brake system message on your dashboard is due to a blown fuse, a bad brake light switch, or a bad trailer brake control switch. It can also occur due to faulty wiring.

1. Blown Fuse

Everything electronic running on your vehicle relies on a fuse to monitor power. If too much voltage moves through the system, the fuse could blow. In some cases, a blown fuse means that there’s a larger problem, which becomes quick to identify if you replace the fuse and it happens again.

Identify the appropriate fuse by checking your car’s owner’s manual and check to see if the fuse is blown. If so, replace it with a comparable fuse to get back on the road.

2. Bad Trailer Brake Control Switch

Under your dashboard, you will often see a trailer brake controller in most car models with a trailer brake system. This trailer brake control switch can fail, which results in a necessary replacement. It’s also possible that the connectors are simply contaminated or dirty.

If you have a Chevrolet with the Service Trailer Brake System warning message, a faulty trailer brake controller switch under your steering wheel is a very common part that causes it.

Your first response should be to clean the connectors and see if that makes a difference. Otherwise, the switch must be replaced.

3. Faulty Brake Light Switch

If the brake light switch fails, the message could illuminate. The good news is that replacing this part isn’t usually expensive.

The brake light switch is located on the brake pedal in most car models, and it is often quite easy to replace it yourself. However, you need to make sure that you make a proper switch adjustment afterward.

RELATED: 5 Symptoms of a Bad Brake Light Switch (& Replacement Cost)

4. Defective Sensor/Master Brake Cylinder

The brake system utilizes a master cylinder and a handful of sensors to ensure everything is running its best. When something fails, it’s possible for the message to illuminate.

In some cases, this message will occur with others, indicating that there’s a larger brake problem occurring. Depending on what sensor has failed, you could be looking at a larger repair bill. 

5. Damaged/Faulty Wiring

When wires fray or get damaged, the signals can’t be sent where they must go. This fault leads to the brake system message on the dashboard. 

If you aren’t skilled at finding electrical faults, this might be a better job for a professional. Every connection and wire needs to be evaluated for damaged before it can be repaired. 

RELATED: 10 Best Trailer Brake Controllers – Review & Buyer’s Guide

Surge vs. Electrical Trailer Brakes

Surge Trailer Brakes

The surge brake setup is hydraulic in nature. It’s the most basic system while still allowing for increased safety on the road. 

The momentum of decelerating your vehicle is used to brake the trailer. This process works because of what’s known as pressure theory. The greater the pressure that is applied to the system, the more braking occurs. With this system, you can make hard stops without causing additional wear to the brake components. 

So far, everything about this system seems favorable, especially the lower price and reduction in effort needed. However, surge brakes don’t give you as much control, which is a big negative for the system. 

Electrical Trailer Brakes

The electrical trailer brakes are easily adjustable. You can modify the force based on how you drive and the braking force that’s needed. With a controller, the braking functions are always easy to manage and maintenance is minimal. You also gain more control with this system than with the surge brakes.

These systems are more expensive. You also have more money out of pocket if you need to get someone to professionally install the system for you. These are all aspects to factor into the cost before you make a decision. 

Could There be an Issue with Trailer Brake Fuse?

The majority of trailer brakes work with a 30-amp fuse. There’s always the chance that the fuse has blown. However, if this is the case, the brakes aren’t going to work at all because there’s no power heading to the brakes. 

If you want to check the fuse, you need to find it first. You can look at the fuse diagram in the owner’s manual to find it. With a multimeter, you can check the 30-amp fuse to make sure it’s getting the right amount of power. If you have to replace it, you want to use the same amperage. Otherwise, you could cause electrical damage to the system.

RELATED: How Much Does a Gooseneck Hitch Installation Cost?

Average Cost to Fix the Trailer Brake System

You could spend anywhere from $0 to $500 to fix the trailer brake system, depending on what’s wrong with it. If an adjustment is all that’s needed, you only need to give up a little bit of time and use your screwdriver. However, there are other situations that are going to cost you money to repair.

As an example, if you need a new fuse, you might spend $5 to $15. Again, this is something you can probably repair on your own. It should only take you a few minutes once you find the fuse. 

Other than these two problems, you might need the trailer brake system parts replaced or it might be time for a complete replacement. The cost of this replacement depends on multiple factors. First, you will spend more on OEM equipment versus parts that are aftermarket. Additionally, you have to consider what make and model you drive, as some are remarkably more expensive to work with. You also have to think about where you are getting the work done, with urban mechanics costing far more than most rural service shops.

RELATED: 4-Pin Trailer Wiring Install – Diagram & Guide

Trailer Brake System FAQs

Is It Safe to Drive With a Service Trailer Brake System Message?

No, there are many messages that can be dealt with later without too much concern. However, the Service Trailer Brake System message isn’t one that you should ignore if you are towing a trailer. This issue is going to create problems when you try to brake with a trailer attached. If you don’t fix the problem and you continue driving, you could start a chain reaction leading to a massive accident. 

How do you reset a Service Trailer Brake System Message?

How to reset the service trailer brake system message depends on the type of trailer brake system your car uses. In most cases, it will go away on its own if you repair the problem that caused it to appear. You may need to use an OBD2 scanner to reset the system, depending on the car model.

How do you reprogram a trailer brake control module?

If you want to reprogram a trailer brake control module, you need a specific diagnostic tool for the trailer brake system your car uses. You can also adjust the trailer brakes manually by using the controller for many brake control systems.

How do you troubleshoot an electric trailer brake controller?

To diagnose an electric trailer brake controller, you may need a specific diagnostic computer that is compatible with the brake controller. However, a multimeter and a wiring diagram for the brake regulator can be sufficient in many cases.

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