An interesting problem that I can't find a solution for by searching this forum. First, the car battery was dead and since it was older I replaced it and then the battery went dead again. I had the battery charged and when I drove it next it acted like it was in transport mode since the windows wouldn't operate, the air compressor doesn't come on, etc. I just took it to a mechanic and they indicate that the car won't communicate at all. Does anyone have any ideas or can someone point me to a similar thread?
Suspect you have alternator/regulator issue if your replacement battery had to be recharged. Fix this first and then have the car transport mode cleared by dealer/independent BMW shop.
Thanks, CD. The battery draws down to the point where it won't start in 24 hours. Does it make sense that with the battery fully charged that it won't communicate? The mechanic that looked at it today is a local independent BMW shop. I brought the car home because the driver's window is partially down and I couldn't let it sit outside. I plan to take it back to them but they seemed perplexed by the inability of the car to communicate at all.
It won't communicate to a diagnostic computer over the OBDII port? If so, there's probably a module on the communication buss shorting it out, could also explain draining the battery. You need a shop with more electronics experienced if your current shop is perplexed with the issue. Systematically disconnecting modules and fuses may help find the culprit. How much current is the car drawing when it's asleep?
I'd try a master battery reset the see the comms come back
I believe by master reset you mean to disconnect the battery. The battery was disconnected for about week prior to taking it to the mechanic.
Parasitic battery drain testing:https://www.youtube.com/watch?v=QRso1A0VScw
Thanks for providing another excellent DIY post. I live in an urban condo with a basement garage where the car currently sits with the battery disconnected. I really don't have many DIY options. The independent garage that laid claim to having BMW experts hasn't called me since discovering that they couldn't read the codes from the car. I'm inclined to agree with @Clearancediver that the alternator/regulator is bad and the car is in transport mode. I can't get through the logic of why that would prevent the codes to display but I am considering the strategy of having the alternator replaced and see what happens when the ECM measures +11.8v on the supply side. Wishful thinking? I'm struggling with a strategy here.
Last edited by phlorida; 08-18-2017 at 09:21 PM.
I would not throw parts at it "wishing" it fixes the problem. The alternator can be tested while it's in the car. What is the battery voltage with the car running when you rev it up? You just need to find a competent shop to diagnose the issue.
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