[crimsoon]

My brother recently bought a well maintained 2006 BMW E90 325i. Everything seems fine, but when he tried to read the oil level it shows INACTIVE. What's strange to me is that the car has a 335i cluster and the oil temperature reading is fine even though that data should come from the same sensor. There's no issue with the water pump running needlessly.
I read the codes and the only one that shows up is 2E7C: BSD communication fault. First I tried disconnecting the violet wire to the alternator since it's easy to reach. 2E7C immediately returns when cleared. Left it overnight, cleared again and still remains.

I put the car on a lift at a friend's shop. I disconnected all BSD devices (alternator, water pump and oil sensor, there's no IBS), cleared the codes (immediately and after ~30 minutes), but the issue still remains.
At least there seem to be no oil leaks as PO replaced all gaskets. The PO also replaced the water pump (Pierburg) and oil sensor (OEM) about a year ago.

Next thing I could think of is that it might be an electrical issue. I did the following measurements:
- no resistance between violet wire on alternator and water pump.
- no resistance between violet wire on alternator and DME (X60005 pin 35). Also no rust on DME pins.
- no short between violet wire on alternator and ground.
- no voltage loss between positive battery jump point and battery strap near valve cover.
I forgot to check the power and ground connection to the oil sensor. Not sure if that might be an issue if the oil temperature reading is still correct.

I installed ISTA+, having faint hope the oil level would work there, but alas it sits at 0. Again oil temperature is fine.

Am I missing something (or doing something wrong), or is swapping the DME the only option that's left?
Is there any other electrical connection I can check? I don't have an oscilloscope to probe the BSD connection.
If I would get a replacement DME, would I be able to check the oil level before sending it to a company to get cloned?

[Roman N52B25]

You really want to get an oscilloscope and probe the BSD line (the one going to alternator is one woth the best acces to it) and look for the square signal - disconnect one component at the time and check again, if you disconnect something and the signal comes back, you will know what causes the distortion of signal in whole loop. Check my thread, I had quite exhausting time with this one...

[crimsoon]

Finally was able to lend an oscilloscope from work. I disconnected the alternator BSD connector and connected a probe to it (grounded to the alternator). If I understand it correctly I'm only measuring a steady ~1.1V (with ignition on). I then disconnected the water pump and oil sensor, but it still gives the same measurement.

So unless I'm doing something wrong, it seems that I have to look for a replacement DME. Seems to be similar test results as this post, which was also a bad DME.