M73: No DME connection while engine is running

[simpadic]

Hello everybody,

I have an 1997 BMW E38 750i that needs some attention currently. Therefore I set up an Dell Latitude D630 with RS232 and an ADS interface to run INPA / EDIABAS there. I have done that several times before on different laptops and for different cars, mainly E39.
Ok, I managed to connect to all of the car's modules including both DMEs. But the connection breaks when I start the engine, which means that I am not able to check any live data while engine is running. Turning off the engine brings up a working INPA again.
There are some errors, when connecting INPA to the DMEs. First, EDIABAS pops up with a window, that is named "OpenConnection" and tells me "CreateFile_Error". When I hit "ok" INPA resumes with the connection process and shows another window named "EDIABAS Error" that tells me "ApiCheckJobStatus: Fehlernr. 18 IFH-0008: Fehlerhafte Verbindung Interface/SG (...) (That translates to: "ApiCheckJobStatus: Error number 18: IFH-0008: Faulty connection interface / module"). When hitting ok, INPA connects to each of the DMEs and lets me read error codes as well as live data. It seems to be a little slow, at least slower than the connection on my E39 540i with OBD interface, but that's not necessarily atypical slow.

So, I could live with both of the errors. I only noticed them because they may be related to the fact, that INPA looses its connection to each of the DME, when starting the engine.
Has anyone any clue, what's going wrong, what I may try, or where I could search for the reason of that behavior?

Thank you all in advance and best wishes from Bamberg/Germany!
Simon

PS:
Here my setup:
Dell Latitude D630 / RS232
ADS interface from do-it-auto.de (they are well known to work on old ADS cars. I used it successfully on an old E34: https://doitauto.de/ads-obd-diagnose...d-inpa-ediabas)
Windows 7 x86
EDIABAS 6.4.3

[328 Power 04]

Have you tried it in OBD mode, or with a KDCAN cable?
The M5.2 has K line as well.

[simpadic]

Thank you for your answer!
Yes, I tried it with the Setup running on a different laptop that is working for my '98 540iT non-TU: K-DCAN interface via USB, OBD mode, 20-pin adapter. It recognizes battery and ignition and lets me read any modul except of the both DMEs. The error message I receive while trying is:
"IFH-0006: Interface akzeptiert nicht das Kommando. Das Programm wird abgebrochen!" which translates to "... interface does not accept the command. Program is terminated!".

[simpadic]

I tried another OBD setup that works well on a friend's E38 with a M73N. It shows the same behavior as my OBD / K-DCAN setup that I mentioned above: No connection to DME at all.
I think, that is plausibel due to the fact, that M73 still transmit ADS protocol instead of OBD.

There is another fact I noticed yesterday: My ADS setup won't let me inside the DME anytime. Sometimes there is no connection and I have to restart INPA / EDIABAS several times. I could not find any pattern or relation to anything else by now.

Dows anyone have any other hint, where to search or what to look for next?

[328 Power 04]

It makes me wonder if the 750i DMEs were wired at all to K-line. When this DME family, M5.2, was used in the M44, it was wired only on the K-line.


L-line itself isn't terribly great for logging due to its low data bandwidth.

[simpadic]

Hello again,

I'm not familiar with the meaning of L- and K-line. As far as I know the 750i pre-TU delivered the DME data via ADS protocoll even if the rest of the car's ecus already changed to OBD. That changed with the M73B54TU. I suppose that that's identical to L- and K-Line, where L-line were used for ADS and K-Line for OBD but I'm unsure about that.
Also one can read about lots of diagnostic problems at the M73B54 pre-TU at least in german forums. Lots of people do not even get to the point where I stuck, meaning the cannot even communicate with the DME. By now, I did not find any hint to the cause of that problem nor any solution. Lots of people seem to simply live with that fact.

But I did some further research and set up a different Thinkpad T42 with native RS232 via its docking station. I used a newer EDIABAS/Inpa version (6.7.4 / 5.0). Using the same Interface as above and the same EDIABAS/Inpa config (ADS and so on) I can connect to the DME without any error. When starting the engine connection breaks and Inpa throws some connection related errors. But it reconnects after a while and then there is live data of the DME. Connection is horribly slow, Inpa throws connection / Interface related errors again from time to time, and its far away from being useful to e.g. search for air leakages by watching the lambda integrators while spraying brake cleaner on the intake; but at least it works.
So, by now I assume that is the best one can get working on M73B54 pre-TU. But I still appreciate any hints if there are some.

@328 Power 04: Even if I don't think so, let me please ask: Is there any way to get to K-line communication if it isn't already wired in that way?