Try cleaning the wheel sensors, located on the front wheels. Pull it out and remove all particles that's clinging on. Sometimes, due to low voltage, ..this system also fails. Check your charging system if it's okay. Check battery voltage, at least 13.4 should register on your volt meter. If it's too low, ..maybe it's time to check and/or replace the brushes on the alternator. It should be easy to do, ....I have to remove two screws , ..pull it out and put the new ones in. ( 420 SEL )....