As a trailer driver, you are responsible for maintaining your vehicle to ensure it performs well. Seeing the trailer ABS light come on whenever you apply the brakes can be worrisome and can be attributed to various factors.
The ABS is an important safety feature designed to prevent wheel lock-up during braking to enhance vehicle stability and control.
When the ABS light comes on, it indicates an issue within the system that requires attention. So, why does my trailer ABS light come on when brakes are applied?
Why Trailer ABS Light Come on When Brakes are Applied and Solutions
Here’s the reason why your trailer ABS light comes on when you apply the brake and how to fix it:
1. Blown ABS Fuse
One of the major reasons why your trailer ABS light comes on when brakes are applied is usually because of a blown ABS fuse. The fuse is a safety feature that protects the ABS system by preventing electrical overload.
If a fault occurs in the ABS system or there is an electrical issue, the fuse will blow, interrupting the circuit and disabling the ABS.
It also protects the ABS components from damage and ensures the overall safety of the vehicle by alerting the driver to address the ABS problem.
However, when the ABS fuse is blown, it can cause the light to come on indicting an issue. Therefore, before looking for other possible causes, check the fuse first and replace it. In fact, whether the fuse is good or not, replace it and test the vehicle again.
Many trailer drivers have given testimonies of successfully fixing this issue simply by replacing the ABS fuse.
So, replace the fuse and if the problem persists, then, you can look for other possible causes.
2. Faulty ABS Sensor
Another reason for the ABS light to come on when brakes are applied is a malfunctioning ABS sensor. ABS relies on wheel speed sensors to monitor the rotational speed of each wheel.
If a sensor fails or encounters a problem, it can send incorrect signals to the ABS control module, triggering the ABS light. Therefore, you need to inspect the sensors for damage, contamination, or loose connections is crucial. If they prove to be the cause of the problem, have the sensors replaced as soon as possible?
3. Wire Problems
If your trailer ABS light comes on when you apply the brakes, it might be a bad wiring or a wire that is cut and touching each other whenever the brakes are applied. What you have to do here is to inspect the brake wires and ABS wires for any cut.
If you had recently just fixed the trailer in an auto shop before the issue start, you may need to trace back the work to be sure there’s no bad wiring going on.
For example, most trailer ABS is equipped to have constant power throughout the 7-way. So, if they are starved of that constant light, it can cause the abs light to come on when the brakes are applied.
As long as this is a new development and not something that use to happen anytime you use the brakes, then something must be terribly wrong. Start with the fuse replacement and check the bad wiring, you may find the cause of the problem.
4. Wheel Bearing Issues
Wheel bearings play an important role in the proper functioning of the ABS system. When wheel bearings are worn or damaged, they can cause irregular wheel speed readings, leading to erroneous ABS activation.
You need to check the condition of the wheel bearings and replacing any faulty components if needed to restore ABS functionality.
5. Loose Terminal Connections
When the terminal connections related to the brakes and ABS systems are loose and not properly tightened, it can cause the ABS light to come on whenever you apply the brake.
The loose terminals connection can cause intermittent communication during the force applied by the brake to stop the trailer and goes away when you release your foot from the brake.
The solution to this would be to check the brakes and ABS connections to be sure they are properly fastened. If anyone is not properly fastened, they should be fastened as soon as possible to solve the problem. Don’t forget the ABS light can be a DOT violation so the earlier you have it fixed the better.
The ABS relies on a network of wiring and connectors to transmit signals between the sensors and the ABS control module. Damaged wiring, corrosion, or poor connections can disrupt communication, causing the ABS light to illuminate when you apply the brakes.
6. ABS Module Malfunction
The ABS control module is the brain of the ABS system, interpreting data from the wheel speed sensors and making decisions about braking. A malfunctioning ABS module can lead to incorrect ABS activation and trigger the warning light.
You can use diagnostic tools to assess the functionality of the ABS module accurately to know what to fix. Replace the module if need be.
7. Low Brake Fluid
Inadequate brake fluid levels can also be a culprit for the ABS light coming on. The ABS system monitors brake fluid pressure, and low levels may be indicative of a leak or a problem within the braking system.
If you have a low brake fluid, top it up and drive the vehicle to see if the light comes on again, if the light never comes on again, then the low fluid is definitely the cause of the problem.
8. Faulty ABS Pump/Motor
The ABS pump or motor is responsible for modulating brake pressure during ABS activation. If the pump or motor malfunctions, it can disrupt the ABS’s operation, leading to the illumination of the ABS light.
You should thoroughly inspect the ABS pump and motor to identify and fix any issues.
9. System Calibration Issues
Changes in tire size or other modifications to the trailer may necessitate recalibration of the ABS system. Incorrect calibration can lead to improper ABS activation and trigger the warning light when the brake is applied.
What you should do here is check the trailer’s manual or seek professional assistance to properly calibrate the system for you.
When Should the ABS Light Come On in a Trailer?
Under normal circumstances, the ABS light in a trailer should come on briefly during the startup of the vehicle as part of a self-check routine. This is a normal operation to indicate that the ABS system is functioning correctly.
However, if the ABS light comes on at other times, it indicates a problem within the ABS system that requires attention.
Here are the situations when the ABS light might come on in a trailer, signaling an issue:
- During Startup And Stays On: The ABS light should illuminate momentarily when you start the vehicle. This is a self-check to confirm that the ABS system is operational. Once the system confirms its readiness, the light should turn off. However, if it stays on, it means something is wrong somewhere with the ABS system.
- ABS System Fault: If the ABS light comes on while driving or when applying the brakes, it suggests a fault in the ABS system which could be due to issues such as a malfunctioning sensor, damaged wiring, low brake fluid, or other ABS-related components.
- Low Brake Fluid: Some ABS systems monitor brake fluid levels, and a low fluid level can trigger the ABS light to come on.
- Wheel Speed Sensor Issues: The ABS relies on wheel speed sensors to monitor the rotation of each wheel. If a sensor malfunctions or if there’s an issue with the sensor circuit, the ABS light may come on.
- Faulty ABS Module: The ABS control module is a critical component of the system. If it malfunctions, it can lead to erroneous ABS activation and trigger the warning light.
- Wiring or Connector Problems: Damage to the wiring harness or poor connections in the ABS system can disrupt communication between components and result in the ABS light illuminating.
- System Calibration Issues: Changes in tire size or modifications to the trailer may necessitate recalibration of the ABS system. Incorrect calibration can lead to ABS activation and cause the ABS light to come on.
Conclusion
The most common cause of trailer ABS light coming on when brakes are applied is a blown fuse, I recommend replacing the fuse first before looking for other possible causes.
If after replacing the fuse the problem persist, you can inspect for other problems such as bad wiring, loose terminal connections, etc.
One you find the cause of the problem, have it fixed as soon as possible as ignoring the warning light can compromise the effectiveness of the ABS system, especially in emergency braking situations.
