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:

[Robin-535im]

Lessons from the story: Consider buying genuine BMW parts when those parts are critical!
http://www.bimmerboard.com/forums/posts/477424
I'm always amazed that stuff like this happens, where you buy a new part from a reputable place and it's just plain designed wrong and doesn't work. I wonder if there is any quality checking in the process, or if they just submit some specs to a fabrication house and assume the parts will be fine? My other car is an old pickup, and while parts are plentiful and cheap, they are so cheaply made that it is common to get a bad part out of the box... and it's difficult to find replacement parts that aren't total crud. Rubber parts that fail after a few months, radiators that leak, fuel pumps that leak, if I get 2 years of life out of ANYTHING from Autozone I'm surprised.

[Tiger]

Great info. BMA sells only the OE for $113. Autohaus has the aftermarket one as shown in that link.

[ryan roopnarine]

i am conflicted about feeling bad for the gentleman. the number in bentley has been wrong since it came out. winfred told me that it was wrong in excess of 4 years ago. the ohmage measurement on his was correct.

[shogun]

Here a comment by Patrick

...the Aftermarket ones are the ones on my 750 E32 1988

Message: Other than initial DK sync I don't rev up above 4500 RPM in my normal commute. Still, the possibility that the Autohauzaz aftermarket type of Crank position sensors potential can cause engine problem is good info. This is not to bash Autohauzaz which is a good company I do business with, but just this specific part. To be fair I did not sense any engine malfunctioning when I brought the rpm up to sometimes 5300 doing the DK sync. There is usually a hesitation at around 4000 rpm the first round of sync process, but the second and third rounds saw no hesitation. My theory is that the EML only needs one round to finish the sync but BMW calls for three rounds in the procedure to ensure no misses.
Patrick C 88 750 159K

[shogun]

and another comment:

Cars: 740I 2000

Cps

Wow......just yesterday I called AutoHausAZ and requested a return to both CPS I purchased.

CPS codes never went away so I tried OEM and it went away. It cost me $129+tax each but it was worth it. Makes me wonder about OEM VS Non when it comes to electronics................

[Ross]

Idle valve spec wrong too.?
I also found that the spec in Bentley for the M50 ICV to be different from a new dealer sourced valve.
Per Bentley The ICV for M20,30 and 50 should be 20 +-2 ohms between term 1&2 and 2&3, with 40 ohms +-4 between 1&3. The V-8s being 12,12 and 23 respectively.
A new dealer sourced valve for the M50 tested at 12.1,10.9 and 22.8. All within spec for the V-8 valve.
My old valve that I had deemed faulty based on Bentley's spec had essentially the same test results as the new one.
My results were far different than the spec given in Bentley. I find it hard to believe 1% made a difference on a crank sensor. Gap was probablt a bigger factor. Who agrees?

[Atl530i]

Weird. I bought a CPS from Autohauz Arizona and it worked great....