How to Tell If an ABS Module Is Faulty? Symptoms and Solutions

The ABS module is the electronic control unit of the system that prevents the wheels from locking during braking. It evaluates signals from the wheel speed sensors and adjusts brake pressure by controlling the valves in the hydraulic unit. On many vehicles, ESP and traction control are also managed by the same unit.

Symptoms of a faulty ABS module

• Constantly lit ABS, ESP or brake warning light on the instrument cluster
• Diagnostic tool fails to establish communication with the ABS unit
• ABS not engaging under hard braking
• Loss of speedometer or speed reading (on some models, speed data comes from the ABS)
• Warning lights flickering on and off, especially over speed bumps or in cold weather

Common causes

ABS modules are exposed to heat, vibration and moisture in the engine bay. The most common problems are cracked solder joints, moisture-related corrosion and voltage issues in the power supply line. However, the most common cause of an illuminated ABS light is not the module but the wheel speed sensors.

How do you diagnose it correctly?

1. Have the fault codes read with a diagnostic tool.
2. Have the sensors, wiring and connectors checked.
3. Have the unit's power and ground lines measured.
4. If the fault code points directly to the control unit, consider replacing the module.

Choosing the right ABS module

Three numbers matter on ABS units: the vehicle manufacturer's number, the module manufacturer's (Bosch, ATE, Mobis) number and the hydraulic unit number. Bosch ABS modules usually have numbers starting with 0 265 while ATE (Continental Teves) units have 10.09xx or 10.02xx as their prefix. See in our part number reading guide to see what's available.

For products listed by part number, see our ABS module products to see what's available.

FAQ

If the ABS light is on, is the module definitely the problem?

No. The ABS light is most often caused by a wheel speed sensor, the wiring or the sensor ring. Fault codes should be read with a diagnostic tool before deciding to replace the module.

Does a replacement ABS module need coding?

On some vehicles, especially models with ESP, the module may need to be registered to the vehicle or coded. This varies by make and model.

Are the ABS pump and the ABS module the same part?

On most vehicles, the electronic module is mounted on the hydraulic pump. On some models the module can be replaced separately; on others the entire unit is replaced.