ABS Reluctor Ring (Tone Ring)

It is on the hub, bearing or driveshaft. Rust can damage it. Some are magnetic encoders in bearings. Cracked or rusted rings are a common cause of ABS warnings on older cars, especially those mounted on driveshafts. Magnetic encoder rings in wheel bearings can be damaged by magnets or debris. A scope or live data showing a dropout at one wheel helps confirm the fault.

The sensor detects passing teeth or poles.

Damaged rings cause ABS faults. Fit bearings in the correct orientation.