Crank sensor problem: A note on Crank sensors

[shogun]

Lessons from the story: Consider buying genuine BMW parts when those parts are critical!
http://www.bimmerboard.com/forums/posts/477424

edit: have copied the text here now for easier access, there is a pic in the link with the OEM and aftermarket part.

Subject: 540i Crank sensor problem: A note on Crank sensors
Author: e34jef : member since December, 2007
Posted on: 2008-01-28 08

I had this problem with a 540i: right at 4500rpm the engine would stumble badly, not be able to rev past 4500 and flashed the MIL. Fault code was always Crank Sensor. I replaced it twice with new parts from Pelican.
Convinced that this was a fuel delivery problem I replaced filters and the fuel pressure reg, gas lines, and removed/cleaned injectors all with no improvement.
The Bentley Manual states that the resistance of the CS should be 540 +- 10% for a six and 1280 +- 10% for a V8 crank sensor. I checked both the Pelican sourced parts and they were 535 and 554. I had the right part number on both parts, but decided in desperation to try a dealer sourced part. The part from the dealer was 550 ohms. I decided to buy it anyway.
I installed the dealer part and the 4500 rpm flameout condition left for good. A reboot according to board member "shogun" resolved the shift point hesitations and cleared up the rough idle. This car is now prefect!
So, the Bentley is WRONG about the resistance data of the two crank sensors and the Pelican sourced part is defective from new.
Why is that part defective?
here's a pic of the two, Aftermarket is black part on left: