E30 M3, E24 635CSi TDC Reference Sensor

This is a reference sensor used for crank position signal for the E24 635 and a top dead center signal for the E30 M3.

The E24 can have a crank position sensor (CPS) in one of two places: mounted in the transmission bellhousing reading the flywheel (early cars) or on the front of the engine block reading the teeth on the front crank pulley (later cars). The BMW parts information does not show a clear cutoff for each so check your car before ordering. The CPS sends a position signal to the DME so the computer knows when the engine is at TDC and can start the car. It's also when the engine is running for ignition timing. If your engine is not starting or running with misfires this is definitely one of the likely causes. Keep one as a spare to avoid downtime or being stranded!

This also sends a TDC signal in the E30 M3 but it's only used during diagnostic tests. The sensor is located on the upper transmission bellhousing, separate from the other reference sensors. It's only sending a signal to the diagnostic connector, not to the ECU itself. One of the problems with these reference sensors is that they all look alike, especially the male pin connectors on the body of the car. The TDC reference sensor itself is shorter and stubbier than the other two sensors on the M3 bellhousing. Unlike the other two sensors it does not have any markings or special features, just a plain black connector. And it's often missing from the car because it is not required to run and previous owners may have removed it to eliminate confusion.

When doing any sort of repair or maintenance there is no replacement for genuine factory parts. Turner Motorsport carries the Genuine BMW brand with pride and has the parts you need to complete your next project with confidence.

This item fits the following BMWs:
1988-1991 E30 BMW M3
6/1987-1989 E24 BMW 635csi

T#: 19368 | Part#: 12521287784
Part#: 12-52-1-287-784
Part#: 12 52 1 287 784
11% off MSRP $229.34
204.77 $204.77
E30 M3, E24 635CSi TDC Reference Sensor