128i crankshaft position sensor - where and how?

[Erik-AA]

Hey, I have a 2010 128i, 6MT. I'm getting a fault code 2A94 crankshaft position sensor.
I have the new part in hand, I read the instructions for 3 series in the Bentley book and on the Pelican website. Sounds easy. But... I removed the undertray, I'm looking up at the rear of the motor on the left (intake) side, and I can't see it. I can't even see the starter motor that the sensor is supposed to be just below? What the...

See attached photo. See the bit or red tape on a wiring harness and see the smaller wire crossing in front of that tape? My best guess is that this goes to the CPS sensor. But it's only a guess. Can anyone confirm or tell me where to look? And how to get at it? What do I need to remove, how big a job is it?

Thanks in advance!

[Erik-AA]

I finally found it but it does not look like the easy job that some sources claim. If you have any hints for me I'd love to hear them. Thanks!

I took off the cabin air filter and the cowl plastic. Looking down between the AC pipes and the back left corner of the intake manifold I can see the sensor. With my 3 foot extension I could probably get a socket on the bolt and remove it. But there is no room to get my arm in there to deal with the connector and remove the sensor.

Maybe I could do that part working blind from below? Or maybe I need to take off the intake manifold as the book calls for on xDrive 3 series?

Has anybody replaced the crank position sensor on a 128i? Any advice is welcome.

[Bimmer128i]

Originally Posted by Erik-AA

I finally found it but it does not look like the easy job that some sources claim. If you have any hints for me I'd love to hear them. Thanks!

I took off the cabin air filter and the cowl plastic. Looking down between the AC pipes and the back left corner of the intake manifold I can see the sensor. With my 3 foot extension I could probably get a socket on the bolt and remove it. But there is no room to get my arm in there to deal with the connector and remove the sensor.

Maybe I could do that part working blind from below? Or maybe I need to take off the intake manifold as the book calls for on xDrive 3 series?

Has anybody replaced the crank position sensor on a 128i? Any advice is welcome.

I have replaced my crankshaft sensor before and I also made a thread regarding it failing. I was able to remove mine from the bottom. After loosening the bolt I was able to hand loosen it off. But the sensor did not want to come out so I had to kind of wiggle the sensor and pull on the connector to get it out. When putting the new sensor in i positioned it from the top and pushed it in from the bottom. Also make sure that the bolt that goes in on the side is snug at least or you will have issues upon reinstalling.

[Erik-AA]

OK, I replaced the sensor and the problem is fixed. Some notes and photos here for the next person who has to do this PITA job.

I got a quote from an independent BMW shop, they wanted $700 to do this job, and were going to take off the intake manifold to get to the part, I guess the book told them this was needed. It's like a $50 part so with that and with the fact that they couldn't even get to it for two weeks (!) I decided to DIY.

See photo in previous posting, you can't even see the sensor from below. And I could not get a hand in there to even feel it. I took off this cover over the fuel lines on the chassis (3 or 4 10mm nuts) and then I could get my hand up there and feel the sensor.

Working from above I removed the cabin air filter and all that plastic, and was able to finally see the sensor. I removed a wire and bracket from the rear of the intake manifold to get better access. (see photo) Then I was able to get a long extender down there, with a U joint and the E torx socket, and remove the bolt holding the sensor on.

Then working from below I was able to wiggle the sensor out, it took some time and some force. I left the wires connected so I could get a good grip on the sensor with the connector. Once it was out I could see the connector and remove the sensor.

Then I fished out the O-ring from the hole, using a long coathanger bent and sharpened into a hook, from above. I was not able to get the right angle on it from below.

I connected the sensor and installed it from below with new o ring and a dab of grease, but was not able to seat it properly. In my experience it does not seat itself if you just tighten the bolt, it will bend the tab and be cocked in the hole.

I ended up installing the bolt loosely, then putting my long extender against the sensor flange working from above, and struck it with a hammer (gently) to pop the sensor into the hole. Be sure it is fully seated before you tighten the bolt. Loctite on the bolt is probably a good idea.

From there it is easy. Checked to make sure the engine started and the code cleared, then put back all those annoying shields and plastic.

I did it in several sessions and did not check the clock, maybe it was a 4 hour round trip with taking off all the plastic and stuff and figuring things out. And I have a lift which makes it easier. If I had to do it again it would be faster, but I think it's at least two hours no matter how you cut it. Not a fun job, and working blind requires a bit of confidence, but it was not a really difficult job. Good luck!

[Thunderguts]

Originally Posted by Erik-AA

OK, I replaced the sensor and the problem is fixed. Some notes and photos here for the next person who has to do this PITA job.

Based on what I can see, the job would be relatively easy with the intake manifold off. Would you agree with this? I'm trying to think of any other maintenance items I should tend to when do my 3IM swap. Since this part is known to fail, I might just replace it proactively to avoid the hassle later with the manifold back on.

[tracer bullet]

Originally Posted by Erik-AA

Some notes and photos here for the next person who has to do this PITA job.

Thanks for the follow up and instructions for anyone in the future.

[Erik-AA]

Yes it would be an easy job with the intake manifold off. I have no idea how commonly this part fails. FWIW my car had 175k miles on it when the failure occurred.

[desertman123]

I took the manifold off and it was cake, but I'm quite fluent with the 3IM swap job anyway.

[Erik-AA]

And now six months later I am removing the intake manifold to replace the starter. Of course they couldn't fail at the same time!