BMW maintenance

R259 Crank Angle Sensor

Diagnosis/Repair Of The Hall Effect Sensor

It was a dark and stormy night… That is usually how it starts out when someone asks why their bike quit and left them stranded on the side of the road. Oilheads and K models use a device called a Hall-Effect sensor to determine the position of the crankshaft for ignition timing. These electronic devices replaced points to provide better reliability but like all electronic devices they sometimes fail. One of the most difficult aspects of troubleshooting these devices is that the failure is usually intermittent and sometimes difficult to reproduce. There are two types of failures which plague our Oilheads, both of which are caused by the sensors and the wiring harness being constantly immersed in heat. First is failure of the device, which is uncommon but it does happen. Second, which is very common on older Oilheads, is failure of the wiring harness