[vince_aust]

John depends on whether sensor is installed or on hand. The sensor is an imbEdded reed switch with high power magnet. The manual advises how to test when installed and running - 2v sine wave on oscilloscope but I guess if it working why would you need to test it unless you suspect it's intermittent.

If you are testing on a workbench a ohmmeter with a piece of magnetic metal to trigger switch will give you a basic test result.

I replaced mine (87) simply because of their age and they switch on every revolution - car is 25 years old so not replacing them was inviting a breakdown. When I removed them all the insulation was broken down due to location near exhaust. They are identical units

These are cheapish! - you only need to buy the cheaper version for BMW or the 928 about $70 from pelican. Use the search tools - there is heaps written on this issue