Weird 2005 Z4 E85 2.5i Electrical Anomalies

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rsubbio

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2005 Z4 E85 2.5i [45K miles] Electrical Issue

Hoping for some advice on an electrical problem I’m having.

My '05 Z4 2.5i hadn’t been started in several months & the battery was completely dead when I attempted to start it a few weeks ago. After fully recharging the battery [battery is only 24 months old & testing shows no bad cells], the car started right up, but lots of things don’t work [to understand the anomalies I’m experiencing, see Diagnostics” section I attached below.] After I turn the car off, the battery goes dead again within 24 hours. I was able to trace a “hot” short from the radio on the fuse panel, so I thought that might be related. I then removed the fuse & the “short” seemed to go away. I recharged the battery again [despite the radio fuse out,] same series of events occurred. Retried several more times - same results. I should mention that after sitting for months, I found that a field mouse had nested in & behind the glove compartment. I suspected that it may have chewed up some wiring inside the dash, but I removed the aluminum dash panels, etc. & all the wiring I see looks pristine. I’m wondering if it could be some kind of control module or wiring harness issue. I’ve talked with car electrical specialists & they estimate that a diagnostic & repair would start at $3K and be as much as $12K to resolve. Street value on the car is only about $12K. I'd guess that a BMW dealer repair would probably be even more, so it sounds like it’s not worth having a dealer/repair shop do it at those prices. Any advice from anyone out there? Does it sound like a “General Module” issue, or some kind of wiring harness issue? Is there another part that might be involved [e.g. some other kind of control module, main computer board, etc.] that might be involved? Any suggestions on how to troubleshoot to identify the failing component? I’d appreciate ANY advice anyone could provide. I’m pulling my hair out & any suggestions to point me in the right direction, I’d be eternally grateful for. I LOVE my Z4 and don’t want to give up on it. Thanks everyone for your kind assistance. - Bob

Z4 Electrical / Battery Diagnostics:
- after full charge:
- Power windows work
- Power rear view mirrors work
- Power seats work (driver & passenger)
- Seat heaters work (both)
- headlights work
- 4-way flashers work (but no dashboard indicator lights)
- Center console door lock button works
- Turn signals work (but no dashboard indicator lights)
- High beams work (but no dashboard indicator lights)
- Horn works
- Interior lights work
- everything works externally; HOWEVER,
- Instrument panel anomalies/failures:
- no turn signals
- dashboard dimming switch
- no headlight indicators
- SRS airbag indicator lighted
- Radio doesn’t work, and even when ‘off’, draws a constant drain of ~.5 amp [should be > 50ma with fuse installed]; removed fuse to clear
- Key fob works intermittently, e.g.:
- for about 15 mins after clearing codes
- for about 15 mins after idling car off
- after turning car off, battery dies again within a few hours[by dead, multimeter shows < 12.0v charge; car won’t turn over

Performed a BMW Computer Reset multiple times after each battery dead event to ensure not in “transport mode”
 
I know it might sound odd …have you tried another Battery..although yours shows good …it could be good place to start.
 
Sounds very much like a k-bus issue. This is the ‘ring main’ that links all the modules. If one is duff it can affect the others.
Have you jump started the car?
The central airbag module can be killed by the spike from a jump start.
Pop out the coin holder behind the handbrake. Under it you can see the module and should be able to reach the electrical plug.
Disconnect it and see if things start working properly.
 
Hi Umfaan & Zed - thank you for the input; VERY much appreciated!! I don’t think it’s a battery issue; after full charge, car starts, but that wouldn’t explain the loss of indicator lights on the dash. I may have jump-started it at some point; more recently, I used one of those “electronic slow chargers” to get it back on-line. It’s about 2300 hours here… I’ll try the airbag module suggestion tomorrow & hope for the best. Again - THANK YOU!!! Appreciate any other feedback that might help - Bob
 
Using logic, if it was running ok before you stopped using it then I doubt any major components failure if simply left standing unless condensation has got in. If battery had fully discharged then recharging it will not fully restore it to full health. I would suggest a new battery or borrow one from someone to test . Make sure battery terminals are clean and bolted up tightly
Only then start looking at other possibilities
 
Mike6 said:
Using logic, if it was running ok before you stopped using it then I doubt any major components failure if simply left standing unless condensation has got in. If battery had fully discharged then recharging it will not fully restore it to full health. I would suggest a new battery or borrow one from someone to test . Make sure battery terminals are clean and bolted up tightly
Only then start looking at other possibilities
Click to expand...
Well.................. you say that but..........................
Wifey left her car unused for a few weeks. Battery didn't completely die, but didn't have much charge left in it.
Fitted a new one but hey-ho, airbag light on and the central module (SIM85) has stopped communicating.
 
Have you used a diagnostic tool like the creater 310 plus. Might just need to delete any fault codes
 
Hi Mike - thx for the input & advice.... re: your suggestions on the battery, don't think that's the issue.... after a full charge, the car turns over & starts strong, but the core issues are still there: all of the components [headlamps, turn signals, wipers, etc.. etc.. work AOK externally, but none of the associated dashboard indicators show up at all... e.g. when L or R turn signals are activated, I walk around the exterior of the car & I can see the signals flashing AOK. But while they're still on, I sit in the car, look at the dash & the associated dash lamps aren't blinking. Same for every other component [see details in the "Z4 Electrical / Battery Diagnostics:" section above. Multiple retries, same results every time. I've tested with a [fairly sophisticated] Foxwell NT650 Elite unit & have cleared all faults... only exception is that it's calling out an airbag issue & you need a much more sophisticated - & expensive - tool which I can't afford. That result adds credence to snuff_zed's suggestion that it might be the "central airbag module" noted in his reply. I haven't yet been able to expose the potentially-faulty component to test his suggestion to remove it & see if things start working. I'm trying to get there. I'll keep you posted. thx - Bob
 
Hi Mike - thx for the input & advice.... re: your suggestions on the battery, don't think that's the issue.... after a full charge, the car turns over & starts strong, but the core issues are still there: all of the components [headlamps, turn signals, wipers, etc.. etc.. work AOK externally, but none of the associated dashboard indicators show up at all... e.g. when L or R turn signals are activated, I walk around the exterior of the car & I can see the signals flashing AOK. But while they're still on, I sit in the car, look at the dash & the associated dash lamps aren't blinking. Same for every other component [see details in the "Z4 Electrical / Battery Diagnostics:" section above. Multiple retries, same results every time. I've tested with a [fairly sophisticated] Foxwell NT650 Elite unit & have cleared all faults... only exception is that it's calling out an airbag issue & you need a much more sophisticated - & expensive - tool which I can't afford. That result adds credence to snuff_zed's suggestion that it might be the "central airbag module" noted in his reply. I haven't yet been able to expose the potentially-faulty component to test his suggestion to remove it & see if things start working. I'm trying to get there. I'll keep you posted. thx - Bob
 
rsubbio said:
I haven't yet been able to expose the potentially-faulty component to test his suggestion to remove it & see if things start working. I'm trying to get there.
Click to expand...
You don't need to do much 'exposing'. It really is as simple as prying out that little coin holder behind the handbrake. Then you can see the plug.
Leave the green fibre-optic connector in place and just fold down the lever on the electrical plug and pull it out.
Then see whether everything else starts to work properly. If it does then, and only then, do you need to delve in and get that old module out.
 
enuff_zed - hi!, I tried following your suggestions; having an issue: I popped out the coin cup behind the hand brake, but it didn't expose the airbag module as expected, only a section of carpet above what I expect is the transmission. It [the carpet section] seems to be permanently mounted by glue or something to that area or section of the center console. I didn't want to rip it out for fear of me mistakenly being in the wrong area & finding out that the airbag module isn't located there. I'll attach a couple of photos of what I'm seeing. Can you confirm if I'm in the wrong area or not, or provide any other guidance? Thx! One more question: when I do locate the module, can I just take it out? That is, do I have to remove the battery cables before I unplug the component so as not to spike any other electronic components? Thx again - BobIMG_7109.jpegIMG_7108.jpegIMG_7107.jpeg
 
Yup you’ve missed it. Behind that is a small plastic container. Right below the storage door. Prise that out.
For the purpose of checking you needn’t disconnect the battery but to be exactly correct you should disconnect it
 
Hi Zed - can't thank you enough for your kind assistance. There's no "change cup" where you describe, only the covered "Roadside Call" and "Emergency Assistance" buttons. Is that what I should pop out to expose the airbag module? Picture attached. Again - Thx!!
 

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rsubbio said:
Hi Zed - can't thank you enough for your kind assistance. There's no "change cup" where you describe, only the covered "Roadside Call" and "Emergency Assistance" buttons. Is that what I should pop out to expose the airbag module? Picture attached. Again - Thx!!
Click to expand...
Well I’m never too old to learn! Never seen that before! But yes, it’s under there. Though in your case I have no idea what extra electrickery will be in your way.
 
Hi again - popped it out & disconnected the clasp. Started the car; no change: all works as expected externally, but no corresponding dash indicators (all stay dark, no blinking lights, etc.) Ra diagnostic with NT530; attached pictures of key error codes (tried clearing the codes several times; always returns to same state of error.) Any other ideas /suggestions? Thx!
 

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Ah-ha! Two other lights on as well.
The ABS/DTC unit (MK60) is also on the k-bus.
It works with EPS and the DME to control stability by comparing steering angle, wheel slip, braking etc. The DME regulates engine power if there is a discrepancy.
We seem to have eliminated the airbag module as the culprit, though there is still that light on??
I still think we're looking at a k-bus issue.
Either the MK60, or possibly a dodgy connection where all the k-bus wires meet. That is under the dash but I'll admit I'm not exactly sure where.

But you also have a potential issue with one of the two ABS pressure sensors, mounted on the brake master cylinder. No2 is nearest the bulkhead.
Keep it simple and change that first, in case it is upsetting other stuff.
 
Rockhopper said:
Haven't we seen similar to this this before as a GM5 issue?
Click to expand...
Well that's on the k-bus too I believe. So potentially that, but don't recall seeing these brake, traction issues from that?
 
I still say possible battery issue. I had all manner of codes thrown on my car. Battery was fully charged but it seems low on amps etc.New battery and everything fine. although yours is only two years old you say it fully discharged on at least two occasions, it is therefore unlikely to fully recharge
Worth swapping to completely eliminate .
 
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