Signs of a Failing ABS Control Module

Mia Bevacqua
March 11, 2019

All new cars sold in the U.S. since 2013 have come with a mandated anti-lock braking system (ABS). The technology reduces wheel lockup during braking by controlling brake pressure to each wheel.

At the center of the system is a computer that controls the system, called the ABS module. The module may also be involved with traction or stability control, hill start assist and even adaptive cruise control.

Signs of a failing ABS module

A faulty ABS module can cause a number of problems. Some of the most common include:

  • Illuminated warning lights: A failed ABS module may trigger many warning lights, such as the ABS indicator, red brake light, traction control light and more.
  • Loss of antilock braking ability: An ABS module that has gone bad will usually prevent anti-lock braking from working.
  • Unintended ABS activation: On the other hand, a bad ABS module may instead activate the anti-lock brakes unintentionally, resulting in random pedal pulsation.
  • Traction control can’t be disabled: If the ABS module can’t make proper decisions, the vehicle may go into a default mode where traction control is on all the time.
  • Driver assistance functions don’t work: Automatic braking, adaptive cruise control and other assistance features may not work if the ABS module is broken.

How to fix the problem

In some cases, a problematic ABS module may just need to be reprogrammed. Certified mechanics have access to service information that tells them whether a module’s software needs to be updated.

If the module can’t be reprogrammed, it will need to be replaced. This can get pricey. Sometimes, the module can be serviced separately from the ABS hydraulic control unit. In other instances, however, the two are integrated and must be replaced together. On some vehicles, the unit is combined with the brake master cylinder and brake booster as well, making replacement of those items necessary.

Some ABS modules may also need to be programmed or calibrated after replacement. And if the module is paired with the hydraulic control unit or master cylinder, the brake system will need to be bled of air once the job is complete.

» MORE: Get an estimate for an ABS control module replacement

How ABS systems work

To further understand the role of the ABS module, it helps to know how anti-lock braking works. All systems have a few essential components: wheel speed sensors, a hydraulic control unit, and the ABS control module.

The wheel speed sensors measure how fast each wheel is turning and transmit the data to the ABS control module.

If the module determines that wheel lockup is about to occur, it activates solenoids within the hydraulic control unit to adjust brake fluid pressure to the slipping wheel or wheels. As a result, the braking force applied to the slipping wheel is reduced, letting it regain traction to prevent lockup.

On most vehicles, the traction control system uses the same components to prevent wheel spin during acceleration.

Mia Bevacqua

About the Author

Mia Bevacqua is an automotive expert with ASE Master, L1, L2 and L3 Advanced Level Specialist certification. With 13-plus years of experience in the field, she applies her skills toward writing, consulting and automotive software engineering.

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