How to Test ABS Module

This instance usually occurs when one or more tires start to tires skid, at this moment they lose their traction. Without traction the vehicle will go in any direction and in some instances completely sideways.

To reduce the risk of traction loss and skid, research shows that an anti-lock system installed in a vehicle will decrease the chance of an accident by up to 18%. This is risk mitigation is reached through controlled rotational speed of each wheel through metering the brake line pressure.

A typical ABS system integrates sensors that are placed near the wheel to monitor their rotation speed. The data is transferred to the computer module, and preset algorithms assure full control by the system over the braking module. This module computes all four while sensor input and this, in turn, check if one of the wheels is turning slower than the rest. In this instance, the system will tell the valve to reduce the brake line pressure and control the pump’s action to make sure the wheel or wheels roll in sync with the others.

However, in the instance that there is no traction issue, the problem of the warning light could be in the sensors. To test your ABS module, you will need to go through a number of steps, and this is what you will need to do:

Step 1: Preparation

Park your car in a level location, all four wheels need to be on the same level. Make sure you have access to all four wheels since you might need to jack up the car and replace a sensor. If you do need to replace a sensor, this means you need to take off a tire, so you will need to know how to replace tires. When replacing a sensor, you also need to remove the brake calliper and pads, so be prepared. You will also need an ABS code reader, there are plenty of models to choose from, but make sure the model you purchase is designed for your make and model of vehicle. Take into account that when the warning light is either blinking steadily or is always on, it means the system has been disabled, Make sure you enable the system after checking it. When the ABS warning light flashes or stays on steadily, it means the system is disabled. An anti-lock warning light will be in different places in the instrument cluster for each car, and it may be accompanied by a red warning light.

Step 2: The ABS Fuse test

All electrical systems require a fuse to ensure they are not damaged from surges. Check the ABD fuse to see it has not blown, if it has, then replaces it. If it blows again, then there is a short in the system. In most cases, a short is either located in the pump motor or in the ABS computer. You will find the ABS fuse in the cars fuse panel.

Step 3: The ABS Wheel Sensor test

The ABS computer monitors the wheel rotation via the wheel speed sensor. This sensor works together with the wheel stator. The wheel stator is usually attached to the CV Joint, the axle brake rotor and in some cases the bearing hub. The wheel sensor is open to the environment, as such it is subject to all environmental and mechanical conditions including temperature, barometric pressure, humidity, vibration and dirt. In some cases, due to these conditions, a sensor can short, so you need a voltmeter to test each sensor. In general, when testing the wheel sensor, if you get any one of these trouble codes C0035, C0040, C0041, C0045, C0046, C0050, C0051, C1221, C1222, C1223, C1224, C1225, C1226, C1227, C1228, C1232, C1233, C1234, C1235 it means that the sensor has either shorted or is unplugged. In this instance, you will need to jack up the car and replace the sensor.

Step 4: ABS computer Test

Locate your ABS computer module on the engine block, turn the vehicle off. If the ABS computer is still running, usually a humming noise, this indicates that one of the control valve coils might have burned out, so you will need to replace that.

Step 5: Stator Ring Test

While you are checking everything, take heed that in some instances a damaged stator ring does not cause a warning light, so it’s a good time to check them. Stator rings can get damaged or dislodged. When teeth are missing the wheel will rotate slower than the other three, and this will cause the ABS system to be in constant operation. Take heed that stator rings are located in different places on different vehicle models.


If you are not a car mechanic or a professional driver, do not do this alone for the first time. ABS systems are delicate and making changes without understanding them will lead to more damage.

Editorial Staff

1 comment

  • I have a abs light on all the time as well as a brake sensor light on all the time, I replaced all 4 abs sensors and both brake pad wear sensors. In this article it says if abs light is on all the time that the abs system is disabled how do I check are test to see if abs is disabled. I did have front driver’s wheel would lock up if I hit the brakes hard but that hasn’t happened since I bleed the brakes and changed rear drivers side clogged brake lines. Would the abs module be the problem and would abs module cause brake wear sensors to stay on as well