2004 545i OBD ii monitors losing memory
 

Hi All. New member here. Thanks for having me. Been a BMW owner for along time and have been loyal to the E38s and E53s. Gotten to know them pretty well.

But..

I recently fell into an E60 2004 545i and I'm having problems with the OBD ii monitors losing memory every time I turn off the ignition. Do these cars have separate OBD ii modules or is it integrated in the DME? Im assuming it is in the DME. I had hoped it would be a faulty power relay or something but I can't find anything. Do these cars have a main relay or fuse for the DME?

Symptoms as follows:

- car starts and runs fine
- no check engine light (do have passenger restarint and airbag warnings and lighting system warning but believe those unrelated)
- when run obd ii scanner upon start 5 monitors are not set (CAT, O2 sensors x2, EVAP, SEC Air)
- can get CAT and both O2 monitors to run and set correctly in a single drive cycle leaving 2 monitors not set.
- as soon as I turn off ignition and turn back on OBD ii monitors go back to same 5 monitors not set

Does this sound like a DME power supply issue or an issue with the DME itself? How does the DME receive its power (to maintain memory and settings) when ignition is off?

Any ideas would be helpful as I can't even attempt to pass CA smog as is.

Thanks

I have the exact same problem with my 2004 545i. Have you had any luck tracking down the issue?

I found wiring diagrams online:
https://www.newtis.info/tisv2/a/en/e...l-unit/q-A6000

Haven't got around to checking everything but maybe those will help you.

Have you made any progress with this?
My E-Test isn't due till October but would like to fix or sadly dump the car depending what it would need.