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Anti-Lock Brake Issues and Repairs

abs anti lock braking system warning light

What are Anti-Lock Brakes?

Fairfax, Virginia – Your Anti-Lock Braking System, or ABS, is a safety feature on your car, truck, or SUV that helps you to maintain control during hard braking, especially on loose, wet, or slippery surfaces. Essentially required for use on all passenger cars since 2013, ABS serves to keep more of your tires in contact with the road by preventing the wheels from locking up and sending your vehicle into an uncontrolled skid.

Many drivers believe that ABS helps them to stop sooner when braking. That may or may not be the case. Sometimes ABS decreases stopping distances, but sometimes it increases them. It really depends on the road condition. But decreased stopping distance is not the primary objective of ABS.

(See the article, “Your Brake Questions Answered”)

When you slam on the brakes in a vehicle without ABS, the wheels and tires lock up – they stop rotating. As the tires begin to skid, only a small patch of the tire is in contact with the ground. When that happens, your ability to steer diminishes significantly. A tire that is skidding has no ability to steer. It only slides.

But a car equipped with ABS works differently. When you slam on the brakes, wheel speed sensors located at each wheel detect when your tires stop rotating and send that information to the ABS computer module. The ABS module, in turn, tells a special hydraulic device (the ABS actuator) to “pump” the brakes to those wheels, releasing them momentarily and effectively preventing them from locking up. This allows your tires to keep rolling in the right direction and helps you to steer your car. So, while ABS may or may not help you stop sooner, it will at least allow you to maintain steering control when braking hard.

How do I know if my ABS stopped working?

When there is a malfunction in the Anti-Lock Brake System, a warning light on the dash illuminates. The ABS has its own warning light, separate from the main Brake Warning Light. It appears as an orange icon with the letters “ABS”, usually inside a circle with parenthesis around it. Under normal conditions, the ABS light will flash momentarily when you start your engine. It is performing a self-test of the system. If the light stays on, or if it comes on during driving, then there is a problem somewhere in the system that needs to be addressed. (Note: If the ABS light and the main brake warning light are both on, refrain from driving your vehicle until it can be inspected by a professional.)

Common problems associated with the Anti-Lock Brake System that will trigger the ABS light include:

  • Defective wheel speed sensor or damaged wiring – The wheel speed sensors send  electrical signals to the the ABS module so that any abrupt change in wheel speed (such as a sudden deceleration or stop) can be interpreted by the computer and the ABS engaged. If either a wheel speed sensor or its wiring become damaged or defective, the system will not have the information necessary to function properly. A technician can use a scan tool to diagnose a faulty sensor or wire and replace the components.

  • ABS module malfunction – The ABS module controls the system. It constantly monitors the information sent from each wheel speed sensor. A problem with the module will prevent the system from operating. Again, a diagnostic scan can help a technician identify the module as a source of the problem.

  • ABS actuator/hydraulic unit not working properly – The ABS actuator reacts to instructions from the ABS module and switches on and off (through a group of solenoids and valves) the hydraulic pressure to the brakes. If the actuator is not operating as it should, neither will the system.

  • Faulty ABS power relay – Power to the system is routed through the ABS power relay. If the relay is stuck or defective, power to the ABS control circuit will be cut off. A technician will pinpoint this problem by testing the power circuit to the ABS.

  • Low brake fluid level – If the hydraulic fluid level in the brake master cylinder reservoir is low, the ABS may not function properly and the ABS light will come on. Make it a habit to check the brake fluid routinely along with other fluids and filters.

What happens when the ABS system fails?

The reason ABS is standard on passenger vehicles is that the system works to help a driver maintain control during hard braking. ABS is an important safety feature on your vehicle. If it fails, make sure to have it inspected and repaired as soon as possible.

Some drivers ask, “Is it dangerous to drive with the ABS light on?” A faulty Anti-Lock Brake System does not mean your brakes won’t work. If the ABS warning light is on, and the main brake warning light is not, your brakes should still work. As long as you still have a firm brake pedal. But if you have to stop on wet or snowy pavement – or on dirt or gravel – you need to know that your ABS will not engage properly if the light is on.

Other drivers, especially those who started driving before ABS was standard, might ask, “Can’t I just pump the brakes myself?” Pumping the brakes was a technique used years ago to produce the same kind of result that ABS is designed for. A driver would press and release the brake pedal rapidly and in succession to keep the wheels from locking up. But it is a poor substitute for ABS. Manual pumping of the brakes is not nearly as fast as ABS, where cycles can occur more than a dozen times per second. And manual pumping increases stopping distances far more than ABS.

If your car does not have ABS, then sure, pump away manually. But if it does have ABS, press firmly on the pedal and hold it down. You will hear a clicking or growling noise as the actuator does its thing. That is normal. Do not “pump” the pedal on a vehicle equipped with ABS. You will defeat the purpose.

An Anti-Lock Brake System that is malfunctioning (as indicated by the ABS light on your dashboard) or one that is used improperly is ineffective at best and hazardous otherwise. Make sure to read your owner’s manual for proper operating tips. And make sure to have a qualified technician at a trusted repair shop inspect, diagnose, and repair the ABS if the light comes on.

This article is intended only as a general guidance document and relying on its material is at your sole risk. By using this general guidance document, you agree to defend, indemnify and hold harmless Hogan & Sons Tire and Auto and its affiliates from and against any and all claims, damages, costs and expenses, including attorneys’ fees, arising from or related to your use of this guidance document. To the extent fully permissible under applicable law, Hogan & Sons Tire and Auto makes no representations or warranties of any kind, express or implied, as to the information, content, or materials included in this document. This reservation of rights is intended to be only as broad and inclusive as is permitted by the laws of your State of residence.

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