BMW E90 ABS sensor and wheel speed signal fault
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Why are the ABS and traction control lights on or flashing on an E90?
The most common cause is a rusted ABS sensor tone ring. Rust raises the ring, so the sensor cannot detect rotation. Symptoms can include several warning lights and traction control that limits power or brakes in corners.
Is the fault in the sensor, the tone ring or the bearing?
In addition to the sensor, check the tone ring and the bearing. At the rear the rings are separate and replaceable, while at the front the ring comes with the bearing. The bearing's magnetic ring can also be faulty.
How do you fix a rusted ABS tone ring?
The proper fix is cleaning or replacing the ring. Check the sensor at the same time, because the ring can catch it and break it. A wrong aftermarket sensor or a cheap bearing can leave the fault unchanged.
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