Why Does My Truck Keep Saying Service Trailer Brake System?

If you own a truck equipped with a trailer brake system and have been constantly seeing the message “Service Trailer Brake System,” you may be wondering why this notification keeps appearing. This article aims to shed light on the possible reasons behind this message and provide you with a better understanding of the issue.

Faulty Trailer Brake Controller

One possible cause for the “Service Trailer Brake System” message is a faulty trailer brake controller. The controller is responsible for sending signals to the brakes on your trailer, ensuring they engage and operate properly. If the controller is malfunctioning, it can trigger the warning message on your truck’s display. In this case, you might need to have the controller inspected and possibly replaced or repaired.

Faulty Wiring Connections

Another potential reason for the recurring notification is faulty or loose wiring connections between your truck and the trailer. The electrical connection between the two is crucial for the trailer brake system to function correctly. Loose, frayed, or damaged wires can result in intermittent or complete loss of connection, leading to the error message. It is advisable to inspect the wiring harness and connectors for any signs of damage or disconnection. Replacing or repairing the faulty wiring should resolve the issue.

Low Brake Fluid Level

Your truck’s brake system works in tandem with the trailer brake system, and if there is insufficient brake fluid in the reservoir, it can trigger the warning message. A low brake fluid level can indicate a leak or a problem with the braking system, affecting your truck’s ability to apply the brakes on the trailer. Check the brake fluid level and look for any signs of leakage. If the fluid is low or there is a leak, it is recommended to have the brake system inspected and repaired by a qualified professional.

Trailer Brake System Maintenance

Regular maintenance of the trailer brake system is vital to ensure its proper functioning. Failure to maintain the system can lead to issues and trigger error messages. Here are some maintenance tasks to consider:

  • Inspect and clean the trailer brake system components regularly.
  • Check for signs of wear and tear on brake pads, rotors, or drums.
  • Ensure proper lubrication of moving parts.
  • Check and adjust brake controller settings as per the manufacturer’s recommendations.

By regularly maintaining the trailer brake system, you can minimize the chances of encountering the “Service Trailer Brake System” message.

Incompatible Trailer Brake System

The compatibility between your truck and trailer’s braking systems is essential. If you recently purchased a new trailer or made modifications to your current one, it’s possible that the trailer brake system is not compatible with your truck or vice versa. Mismatched or incompatible braking systems can trigger error messages and may require either an upgrade to the braking system or finding a compatible trailer for your truck.


Experiencing the message “Service Trailer Brake System” on your truck can be a frustrating ordeal. However, by understanding the potential causes behind the issue, such as a faulty trailer brake controller, faulty wiring connections, low brake fluid level, lack of maintenance, or incompatible brake systems, you can take appropriate action to rectify the problem. It is always recommended to consult a professional mechanic or technician to diagnose and resolve the underlying cause to ensure the safe operation of your truck and trailer.