08 4.8L cascade FAILURE of every system....!?!
 

Hey Guys,

2nd time it's happened.. Driving in town, air shuts off.. Then cascading error messages of every system shown about every 30 seconds on the idrive screen. Finally stalled at a stop light. Called roadside, after an hour wait the tow guy gets in and it starts right up. Anyone know what this is?!?! My gold extended warranty doesn't cover Nav or "any part related" ... So is this a sensor issue? Battery? Or is this a bad computer?

check the battery under a load - the car will shut off non-essential systems first as the voltage drops (or spikes), and then it will shut off the fuel management... since it started right up, check the alternator - besides, it is a good idea to read the stored codes with bmw-specific software, to see what lead to cascading chain reaction...

you need bmw specific reader that will dig into the modules for stored faults - regular OBD reader will give you industry standard info... the specific codes will tell you if there was a spike in voltage at certain mileage (in kms), the generic reader will tell you that you had O2 sensor failure or too lean/rich condition... choose your mechanic based on their tools/software...

Look at the the left (neg) post on your battery, should see a "date code" stamped in the post. If it coincides with the built date of the car (+/-), chances are that is the original battery and it's on its way out ...

I am nursing mine along with a battery tender, every night!

You guys were right! It was the battery. Dealer wanted $500... quick call to autozone found one in stock, with the same specs, and a longer warranty for $169. Took me about 10 min to install in the parking lot with absolutely the wrong tools. Funny thing is... when I opened it up... battery in there was a lower priced one from Autozone as well.. still under warranty! Although... they wont honor the warranty unless i had previous owners info, which of course i dont. (sort of a scam). In any case its fixed! Thanks for all the help....

^ don't forget to programatically register your new battery with the DME (computer). Any good indy shop can also do this for you (for like $75). Or you can just risk sporadic issues & errors in the future.

http://www.bimmershops.com/near/los-angeles-ca/

Will do ASAP!!

****UPDATE****
 

So, after new AGM battery went in... and paid $100 for "battery registration", it died again, with all systems shutting down in rapid progression. I left it for an hour, restarted again and (without using any electric equipment) got it to my independent mechanic. Within 5 min his voltage tester confirmed what I had argued with Beverly Hills BMW over the first time... bad alternator. I was having voltage swings from 9-15 volts... so the battery was only charging occasionally. Now... this seems like a pretty easy test which really infuriated me, thankfully i didnt spend $560 on a factory battery so I was only out $280 for the aftermarket one & registration. However... how do service techs not catch such an easy to diagnose problem and just push me out the door with a prescription for a battery?!

CPO warranty had a new alternator in the next day for $50, also the service dept at Century West BMW in north Hollywood is much better than my experience at BH BMW.

..because 90% of them are idiots. Not kidding.

Good info.

I wonder if we will eventually see a pattern of abnormal drain- excessive charging cycles- batteries wearing out- alternators failing....

OP, if this is 3 batteries on an 08, that is unusual, IMO. Lets hope this is it. If the battery fails in 2-3 years you may want to look at parasitic drains....