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      10-06-2016, 08:56 AM   #4
Mick70
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Drives: Z4 sdrive35i (before: 23i)
Join Date: Nov 2009
Location: Germany

iTrader: (0)

Funny story - this is how I found out that my Z4's battery was dying:

My Z4 has started last month going into limp mode and throwing various strange error codes, all referring to throttle valve and intake (2CF6, 2CF7, 2D2E), this happened almost daily.

So I read a lot and tried to find a possible solution without bothering the dealer. Strange enough, at first I did not find a clear solution that seemed to help at least in a relevant number of cases. All common proposals, such as replacement of throttle head, pressure tests, control of ECU wiring harness etc., were to no avail in almost every case on E90post.com, n54tech.com and several other forums.

Finally I found a sidenote in a German forum that the E85's (!) ECU was very delicate in case of voltage fluctuations that may appear if the battery isn't the best anymore and a high load is switched on (e.g. headlights, roof mechanism, electric steering). Indeed, I could bring the error messages in connection with such events (e.g. entering an underground car park, driving in dusk, closing the roof while parking the car).

So I simply replaced the battery with a new Varta AGM 70Ah/760A battery from Amazon and registered the battery to the car with Mycarly. No problems ever since (3 weeks now).

BTW: The clock was still fine. But the battery voltage immediately dropped from 12,5V to 11,8V when engaging the central lock system...

Costs:
- Battery: 140€ ~ 156USD on Amazon
- Additional inapp Purchase in Mycarly: 10€ ~ 11USD. Of course you don't need the app at all if you have INPA or Rheingold.

Best regards

Mick
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