What Does the ABS Light Mean?
When your ABS warning light comes on, it means something within the antilock braking system is malfunctioning. You may see the ABS warning light come on or notice a difference in the way your brakes perform. Sometimes the ABS warning light may illuminate even when your brakes work fine.
This often means that the hardware that makes up your braking system is working well. The problem may lie with the sensors that activate the antilock braking system. In this case, the most likely culprit is an ABS wheel-speed sensor on one of the wheels. Here’s a guide on how you can diagnose and fix one or more wheel speed sensors.
How to Diagnose ABS Wheel Speed Sensors
Why Is My ABS Light on?
When the ABS warning light turns on, a part in the antilock braking system is not working. Usually, an ABS warning light turns on for a defective ABS wheel speed sensor.
There are several other reasons why an ABS light could illuminate. The other causes include low brake fluid, a bad ABS module, a faulty bulb check, and a worn hydraulic pump.
Symptoms of a Defective ABS Wheel Speed Sensor
The best way to diagnose a wheel speed sensor that’s malfunctioning is to hook up a scan tool to your car’s computer and check the trouble codes for the problem. In this case, the ABS warning light could generate a C0050 code. This is for an erratic signal or low signal amplitude from one of the wheel speed sensors.
With the scan tool hooked to the car’s computer, check the values for all the wheel speed sensors while driving. Alternatively, you could raise your vehicle, hook up the scan tool and rotate the wheels manually. You should see one whose values do not match the others. It could be a front wheel speed sensor or a rear-wheel speed sensor.
How to Fix the ABS Light When the Brakes Work Fine
1. Remove the Wheel and Check the Wires
Wheel speed sensors are built into the wheel’s hub. They have a small pointed part that reads how fast the wheel is moving. This is with the help of a tone ring that is hooked to the axle hub. The sensor monitors the movement of the teeth found on the tone ring.
If the sensor is out of alignment, dirty, electrically faulty, or broken, the car cannot tell how fast a particular wheel is moving. To get to your sensor, you’ll need to remove the wheel. You can start by manipulating the wires to see if you’ll get a skewed reading on your scan tool or if something changes. You’ll also want to check if there’s a break in any of the wires.
2. Check the Condition of the ABS Tone Ring
If everything looks fine, you’ll need to check the condition of the tone ring, you might have to take out the caliper and rotor to access and inspect it. It could be broken or rotted. This affects the sensor’s ability to read the speed of the wheel. If it’s damaged, the best solution is to replace it.
3. Disconnect the Positive Battery Cable after the Repair Is Done to Reset the ABS Light
It’s advisable to disconnect the positive battery cable once you put everything back together. This helps reset the car’s computer. Once that’s done, drive around with your scan tool connected to see if the wheel speed sensor is still sending an erratic signal. You also want to see if your ABS warning light comes on.
4. Check Other Parts If the Speed Sensor Is Working
Parts that may turn on an ABS warning light
- ABS wheel speed sensor
- Low brake fluid
- Bad ABS module
- Faulty bulb check
- Worn hydraulic pump
If the steps above don’t turn the light off, check other areas to see what could be causing your ABS warning light to illuminate.
How to Replace an ABS Speed Sensor Yourself
Find how-to videos specific to many years, makes, and models in 1A Auto’s how-to video library and replace an ABS wheel speed sensor yourself.
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