[Diy_efi] Diagnostic TDC sensor on an old BMW

Torbjörn Forsman torbjorn.forsman
Tue Apr 11 20:28:14 UTC 2006

Typically, such sensors use to give between a few volts and up to, say, 
20 volts p-p, very much depending on the load resistance. By choosing a 
suitable load, the p-p voltage can be kept relatively independent of the 
engine rpm. It is probably best to connect a scope and do some 
measurements with various load resistors connected (probably in the 
range 1 kohm - 10 kohm). If it isn't possible to run the engine for the 
moment, it might be useful to set up the vibration damper on a lathe, 
drill press or distributor test rig, and put the reluctance sensor at 
the same distance from the damper as on the engine.

On most german cars with a diagnostic "TDC" sensor, it will not give a 
signal at TDC but at 20? BTDC.

Best regards

Torbj?rn Forsman

Tomas J. Sokorai Sch. wrote:
> Hi guys, 
> Any of you know what are the p-p voltages at mid-RPMs of the variable reluctance TDC sensor on the front vibration damper of an old M20 BMW engine (K-jet, M20B23) that's connected only to the dealership diagnostic connector?
> I'm trying to use it for triggering a 3.1/2.8 GM DIS ignition module.

More information about the Diy_efi mailing list