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Anti-lock braking systems (ABS) started to become commonplace in the 1990s. Now, the technology is found on all modern vehicles.
If you’re old enough, you may remember having to “pump the brakes” in an emergency situation to prevent the wheels from locking up. Well, guess what? Thanks to ABS, the car does all that pumping work for you. All you need to do is step on the brake pedal.
At the heart of the ABS system, you’ll find a computer, referred to as a control module. The module uses ABS speed sensors to measure how fast your car’s wheels are turning. If the sensors indicate wheel lockup is about to occur, the control module pulses brake fluid to the slipping wheel (s) to prevent lockup.
An ABS speed sensor – also known as a wheel speed sensor – gauges rotational speed by reading a toothed ring. Usually, the ring is attached to the car’s axle or hub assembly.
Most late-model cars have four ABS speed sensors – one at each wheel. Older applications, however, may have only one or two such sensors. An example is the rear-wheel antilock (RWAL) system, which is often found on pickups, that uses only one differential-mounted speed sensor.
An illuminated ABS warning light is the most common sign of a faulty ABS speed sensor. Other warning lights, such as traction control and vehicle stability control, may pop on, as well. When the ABS light turns on, the control module will store a corresponding diagnostic trouble code (DTC) in its memory. A professional mechanic can use that code as a starting point for further troubleshooting.
If there’s a problem with one or more of the speed sensors, typically, the ABS module will disable the ABS system entirely. If the car has traction and stability control, those systems may also be inoperative since they are integrated with the ABS system.
Do you have a late-model car with advanced driver assistance systems (ADAS), such as automatic emergency braking and adaptive cruise control? If the ABS system isn’t working right, some ADAS functions, such as these, may also be disabled.Get a Quote 1-Year | 12,000-Mile Warranty
We’re talking about your brakes here. If the ABS light is on, that means there’s a problem that could reduce the safety of your car in an emergency-braking situation. As such, you should get the issue diagnosed and repaired immediately.
1-Year | 12,000-Mile Warranty