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Hey everyone, my 2004 Z4 2.5i is driving me nuts. I've been googling, and trying to fix this thing for over a month, and it just refuses to be civil.

Garage kept, only 50,000 miles on it, it looks like new. Out of nowhere, the battery was dead in the garage one morning. Hooked the charger up, and left it for a couple of days to slow charge. It never charged. Here's the weird stuff I saw. All with the key out

P light was on by the shifter (Automatic)
The light around the headlight knob was lit, but no other dash lights were


There was a draw of over 2a if my charger wasn't charging it. The battery was old as dirt anyway, so I bought a new one. Started it up, drove it, seemed fine. Apparently every answer on the internet was "Get a new battery", so I wanted to get that out of the way

Parked it in the garage, shut it off. Started walking away, and the headlights turned on, taillights turned on, and all the dash lights turned on.


Did lots more research, found what seemed to be the holy grail of fixes, the airbag control module. Pulled mine, low and behold, lots of green corrosion. Sourced a new one from a desert based parts yard. Got it in, clean, immaculate, looks brand new. Cleaned the connector, plugged it in, started the car, drove it around. Shut the car off, no more lights! Did a drain check, saw the amp draw slowly go way down, module by module. Success?? Maybe. Left it for a week, checked the battery, still at 12.7v! Can I finally put all the interior back in it!? I open the door, and the headlights turn on... Same crap again. No check engine light, no airbag light. No codes. What in the world did BMW do? Has anyone else seen this happen? Any other modules that these things like to eat? I am about to roll this thing down a hill.. :(.
 

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I would. Seems the problem has been solved. The electronics of the Z4 seems to be made in a primary school. Very poor quality!
 

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The Arkleyologist
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Vladi...do you have an insurance company "monitor" that plugs into the OBD II connector? (Such as "Drivewise" from Allstate?) These have been known wreak havoc with the bmw electrical system.
 

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Do you have any aftermarket electronics installed? Had you replaced anything prior to the problem starting?
 

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Vladi...do you have an insurance company "monitor" that plugs into the OBD II connector? (Such as "Drivewise" from Allstate?) These have been known wreak havoc with the bmw electrical system.
Nope, I use a laptop with the official INPA software for diagnostics and NCS Dummy for coding. One also needs a K-can bus cable in order to be able to use these software bundles. That's what is used in the garages and that's all one needs.
 

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OP - I didn't see you mention if you had coded the new airbag module when it was replaced. It needs to match the VIN of your vehicle or else you can continue to have faults (or indications of faults). This from Pelican Parts website:
Code and program the airbag control module using a BMW scan tool, as needed. The VIN is stored in multiple modules, including the airbag module. If the VINs don't match, faults will be set. Remember to clear any fault codes when complete.
Link:
https://www.pelicanparts.com/techarticles/BMW_Z4M/162-ELEC-Airbag_Module_Replacement/162-ELEC-Airbag_Module_Replacement.htm
 
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