A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
OOleg’s tip: it’s not always the sensor
It may not be the sensor itself but what it reads the signal from: the tone ring on the hub or axle shaft, or, on many cars, a magnetic ring that is built into the wheel bearing itself. Dirt, rust, a crack or damaged teeth, or bearing play — and there’s no signal even though the sensor is fine.
Remove the sensor and, turning the wheel slowly, look at the tone ring: are all the teeth intact and clean? Rock the wheel by hand — bearing play also disrupts the signal. The magnetic ring isn’t replaced separately: it’s part of the bearing.
Possible causes
- The tone ring or the bearing’s magnetic ring: a crack, dirt, stuck-on metal shavings, bearing play
- The sensor isn’t seated properly: too big a gap to the ring, or rust under the sensor
- This wheel’s speed sensor
- Tires of different sizes or pressures
What you can do yourself
- With this fault ABS usually switches off: the ordinary brakes still work, but without ABS the wheels can lock. Brake smoothly and leave a bigger gap, especially on slippery roads.
- Inspect this wheel’s sensor and its wire up to the connector: dirt, corroded pins, chafed insulation. Clean the connector, remove the sensor and clean its tip and its seat of dirt and rust.
- Check the tone ring or the bearing’s magnetic ring: cracks, damaged teeth, stuck-on metal shavings. Don’t clean a magnetic ring with a magnet.
- A scan tool’s live data shows each wheel’s speed: while driving, this wheel should read the same as the others.
Stop and don’t drive on if:
- The red brake light is on, or the brake pedal feels soft or sinks
- The steering became very heavy, or the car pulls to one side when braking
The explanation comes from the error code reference in the AvtoElektrik PRO app.