Diagnostic not working on M3 E36

[jimcob]

Hi!

I need your advice with the problem I'm facing with my M3 E36 Euro.

The car has a loss of power specially in low revs, with a hesitation when trying to accelerate, and allot of exhaust fumes.
I took it to a BMW workshop, and when the technician connected the diagnostic system (Modic) there was no communication with the ECU, so he could diagnose.
Do you have any idea of what it may be wrong?

Thank you in advance,

Best Regards,
Dimitri

[ADS]

Sounds like it's probably one or more coils. they can be removed and Bench checked for resistance values.
On the OBC port under the hood, sometimes pins get pushed down or the connector doesn't make a good connection. Get some q-tips, wrap some fine 400 or 600 grit sanding paper around it, and mildly clean the pins/holes, then get some rubbing alcohol and clean with that. Inspect the pins to make sure none are pushed out - but I'm not sure if any are recessed on purpose from the rest - best to look at another E36 to make sure.

This forum is pretty dead, try M3forum dot net or b i mmer forums dot com (remove spaces and . replaces dot) for more user traffic and answers.

ADS

[jimcob]

Thank you for your reply.
I will follow your instructions and clean the pins/holes.
After searching on the web I found also this explanation from a BMW expert:

sometimes some module pulls down diagnosis bus and you cannot diagnose your car at all.
to find out which module it is you have to disconnect all modules one by one and try to diagnose your car. when diagnosis bus starts to work you have found your problem.
ecu
central locking module
airbag
abs
speedo
automatic gearbox module
ews
and so on

i do many diagnostics on engines ( 20-40 cars in week) and sometimes have this trouble. when i am in a hurry i just disconnect white yellow and white purple wires from connector that connects engine wiring harness to car main harness and i can work with ecu.in older cars its 1 car from 20 that has this problem.
disconnecting these wires will not help you to diagnose your airbag problem so you have to go through this module disconnecting procedure.
other way is to cut these wires just after diagnostic connector, cut them next to airbag module and connect diagnostic connector wires directly to airbag diagnostic module wires.

[JKRIT]

Bad O2 sensors can also cause the symptoms U described, even without setting of the CE light or throwing a code. U really only need to change the pre-cat ones (if they are bad); The post-cat sensors are just monitors and will not make it run badly.

Mass Air Flow sensor is another possibility.

It is had to determine what is wrong without being able to read the codes. These are two that come to mind.
'01 325it Steel Blu./Blk
'98 323is Arctic Sil./Blk, SP
'97 528i Montreal Blu./Grey
'95 M3 Cosmos Blk./Blk

[jimcob]

Thanks for your post.
Both sensors are new.. my problem is that I cannot find out what causes the error in communication between the ecu and the diagnosis..