Introduction:
The safety of semi-trailers in the driving process is very important. The application of ABS in the braking of vehicles is of great significance to improving the security and stability of cars in the process of driving. And the trailer ABS light can play a crucial role. The ABS light on trailer is flashing. This indicates a fault in the system, and its stable working condition is affected. Today I will share some common failure cases and maintenance precautions for the ABS braking system. I hope this helps you when the trailer ABS light comes on.
What is a semi-trailer ABS?

Let’s start by understanding what a semi-trailer ABS is. The semi-trailer ABS refers explicitly to the anti-lock braking system, which is an additional device on the original car braking system to control the stability of the car body during the braking process. The ABS is mainly composed of three parts: wheel sensors, controllers, and regulators. After braking, the ABS mostly achieves the vehicle’s stable control goal by controlling the wheels’ slip rate and wheel speed. The semi-trailer brake is generally an air brake, and the air source comes from the tractor. There are three main parts: emergency relay valve, trailer ABS and brake air chamber. Most failures come from these three large pieces in the absence of air leakage due to improper sealing. Of course, the problem is all-around. All parts related to the air brake will have varying degrees of impact, so the installation should not be taken lightly.
What Does the ABS Light on a Trailer Mean?
The trailer ABS light is a warning indicator that is part of the Anti-lock Braking System on a semi-trailer. This system is designed to prevent the wheels from locking up during braking, which can cause skidding and loss of control, especially in adverse weather conditions. When functioning correctly, the ABS helps maintain stability and steerability during an emergency braking situation. The trailer ABS light typically illuminates on the dashboard or the trailer unit itself when there is an issue with the ABS system. This light serves as an early warning sign, allowing drivers to address the problem before it escalates into a more severe issue that could compromise road safety.
Is It Safe to Drive with the ABS Light On?
One of the most common questions drivers ask is whether it’s safe to drive when the ABS light is on. The answer is nuanced. While your vehicle’s standard braking system should still function, driving with the ABS light on is not ideal. The ABS system is a critical safety feature designed to help you maintain control during emergency braking. If the ABS light is on, it means this system may not work properly, increasing the risk of skidding or losing control, particularly in wet or icy conditions. Therefore, it’s advisable to get the issue checked and fixed as soon as possible to ensure maximum safety on the road.
Common Reasons for the ABS Light on a Semi-Trailer
When the ABS light on a semi-trailer turns on, it indicates a malfunction within the ABS system. Several factors could cause this light to illuminate, and understanding these reasons can help in diagnosing and resolving the issue effectively:
- Faulty Wheel Speed Sensors: The ABS system relies on wheel speed sensors to monitor the rotation of each wheel. If one of these sensors is damaged or fails, it can trigger the ABS light. This is one of the most common causes of the ABS light coming on.
- Wiring Issues: The ABS system is controlled by a network of wiring that connects the sensors to the ABS control module. Any damage, corrosion, or disconnection in the wiring can cause the ABS light to come on.
- Malfunctioning ABS Control Module: The control module is the brain of the ABS system. If it malfunctions, it may not process the signals from the wheel speed sensors correctly, resulting in the ABS light illuminating.
- Low Brake Fluid Levels: While less common in trailers, low brake fluid levels in the vehicle’s braking system can sometimes cause the ABS light to activate. This typically affects the entire braking system, not just the ABS.
- Blown Fuse or Bad Relay: A blown fuse or a faulty relay in the ABS electrical circuit can cause the system to stop functioning, triggering the ABS light.
- Worn Brake Pads or Rotors: Excessively worn brake pads or rotors can affect the ABS system’s performance, leading to the ABS light turning on as a warning sign.
ABS inspection
1. Check whether the connection status of various devices and firmware in the ABS is tight, especially the installation of connectors and cables, and analyze the interference coupling effect of related components and other components. The devices that cause interference should be improved and improved. The upgrade promotes the normal operation of the ABS. In addition, it is necessary to place the trailer ABS light in the “on” position, turn on the car’s power, and check whether the trailer ABS light is displayed normally. 2. Keep the semi-trailer in the running state, and the vehicle speed is 10 kilometers per hour; at this time, the ABS light on semi trailer is in the off state, and it can be determined that the semi-trailer’s ABS is operating normally. If the trailer ABS light is flashing, the ABS is not functioning normally, and its stable working conditions are affected. At this time, the driver should continue to observe the flashing frequency of the trailer ABS light. Different frequencies correspond to fault codes, which must be based on the actual situation. Determine the type of failure, and take targeted improvement measures. For example, if the trailer ABS light flashes alternately with an interval of 1 second, the fault code is 1.1. The specific meaning is that the exhaust solenoid of the left front regulator has a fault. The troubleshooting method is maintenance or replacement.
Why is ABS light on a semi trailer?
If the trailer ABS light is on, this indicates a fault in the system, and its stable working condition is affected. You may need to check all of your wheel sensors. You may have a loose or dirty connection. It is worth mentioning that driving with your trailer ABS light is a bad idea. This is because it indicates that your ABS is not functioning correctly. Your vehicle may not be able to handle heavy braking as it was designed. This is an emergency situation; you should immediately stop driving if your trailer ABS light comes on.
Common faults and solutions
1. The air pressure has been lower than 0.7MPa for a long time, or the trailer has obvious drag brakes during the driving process. The processing method is as follows: a. Replace the front of the car and troubleshoot the tractor. b. Check the source of air leakage by applying soapy water, and eliminate “air leakage at the handshake connection,” “pipe joint leakage,” “brake chamber air leakage,” etc. If it exists, you must check whether the valve body enters water or can see apparent rust. This phenomenon indicates that the trailer air pipeline is not well filtered and dried, and the valve body may need to be replaced. 2. The trailer cannot be started after being parked and has been locked. The processing method is as follows: a. First, unplug the ABS spiral wire to see if it can normally start to eliminate circuit problems. b. Put the tractor in the inflating state, unplug the air pipe of the manual valve, and check whether the air pressure of the air outlet is normal (the air pressure should be huge in the inflated state). c. Check whether the parking brake is in the released state. d. If there is no problem with the gas circuit inspection, check the axle content for mechanical failure. In all braking states of the trailer braking system, the safety design ultimately keeps the air supply pipeline unblocked. Both the foot brake of the tractor and the parking brake measures are effective by supplying air to the control pipeline.
Tips for daily maintenance of trailer braking system
No one wants to see their trailer ABS light on all the time. After all, when your trailer ABS light comes on, it means there is a fault that you need to deal with. Here are some daily maintenance tips for the ABS on semi trailer. 1. After receiving the new car, check whether the ABS is working correctly. The working status of the ABS is still checked before the car is reviewed every year. 2. Regularly replace and clean the dryer and filter of the tractor to prevent the dirt in the pipeline from damaging the ABS. 3. Every 15 days in winter (monthly in summer), clean the accumulated water in the leading vehicle and trailer air tank, especially in winter. 4. Every time the axle is maintained, or the brake shoe is replaced, the dust or oil on the surface of the sensor and gear ring should be removed in time. 5. When replacing or maintaining the sensor, pay attention to whether the clamping force between the sensor and the elastic bushing is appropriate (the clamping force should be 120~200N). If it is too small, the elastic bushing must be replaced. 6. Check the ABS wiring harness and air circuit every week for wear, interference, peeling and aging, electric leakage, and air leakage. 7. Check and clean up the dust, rust, and other dirt inside each plug connector every month. 8. Check whether the ABS regulators and ECU fixing bolts and nuts are loose every month and tighten them in time.
Trailer ABS light codes
The method to obtain the flashing code when the trailer experiences ABS failure. What should you do next when Wabco trailer abs flashes codes 3, 4, 5, 6, 7, 9, 10, 11, 14,15, 16, 17, 18. See the following figure for details:

How to Reset ABS Light on Your Trailer: Simple 6 Step Process
If you’re dealing with an ABS light on your trailer, one common method to reset it involves pressing the brake pedal multiple times. Here’s a simple, step-by-step guide to resetting the ABS light:
Step 1: Ensure Safety First
Before attempting any reset procedure, make sure your vehicle is safely parked in a secure location. Ensure the ignition is turned off, and the parking brake is engaged.
Step 2: Turn On the Ignition
Turn the key in the ignition to the “On” position, but don’t start the engine. This allows you to access the truck’s electrical systems without engaging the engine.
Step 3: Press the Brake Pedal
Firmly press the brake pedal. You need to engage the brakes to communicate with the ABS control system.
Step 4: Press the Brake Pedal 6 Times
While pressing the brake pedal, press it down six times in quick succession. This simple trick helps reset the ABS system and may clear the malfunction. Be sure to do this promptly, without long pauses between presses.
Step 5: Turn the Ignition Off and On
After completing the brake pedal presses, turn the ignition off. Wait for about 10 seconds and then turn the ignition back on, but don’t start the engine. The ABS light should have turned off. If it doesn’t, repeat the process once more.
Step 6: Test the Brakes
Start the truck or trailer and drive it for a short distance. Ensure the ABS light remains off, and check if the brakes function correctly. If the light comes back on, there may still be an underlying issue that requires further inspection.
Resetting the ABS light on your trailer might seem like a simple process, but it’s essential to address the underlying cause to ensure your vehicle’s safety. By following the steps outlined in this guide, you can potentially reset the light and resume safe driving. However, if the issue persists, seeking professional help is crucial. Ignoring an ABS malfunction can lead to dangerous driving conditions and legal consequences, so it’s best to act swiftly.
Make sure your ABS system is always functioning optimally for your safety and peace of mind.
Conclusion:
In layman’s terms, ABS acts like a driver’s “spot braking” quickly and frequently, but the driver’s “spot braking” frequency cannot be compared with ABS in any way. ABS only works when emergency braking causes the wheels to lock up. When a vehicle equipped with ABS encounters an emergency braking in a dangerous situation, the clutch should be stepped down quickly, and then the foot should be slammed to brake. At the same time, the steering wheel can still be turned to make the vehicle avoid obstacles. If the trailer ABS light is on while the car is running, the ABS is malfunctioning. If you don’t deal with it in time, many safety and quality accidents will be caused. Therefore the role of ABS on semi trailer should be taken seriously and maintained promptly. The trailer ABS light is more than just a warning; it’s a crucial indicator of the health of your semi-trailer’s braking system. By understanding what the ABS light on a trailer means, the most common causes of it turning on, and how to fix it, you can maintain safety on the road and prevent costly repairs. Regular maintenance and prompt attention to any ABS issues will ensure that your semi-trailer remains in top condition, providing peace of mind and safety for every journey. If the ABS light comes on, take it seriously—it’s better to fix the issue early than to risk driving with a compromised braking system.
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