Auto start/stop fault e91

Discussion in 'Technical Troubles' started by PDoddy, Sep 13, 2019.

  1. PDoddy
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    PDoddy

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    Hi all,

    I haven’t posted on here for ages, but hoping someone might have some advice from experience...

    Ages ago the auto start/stop feature on our e91 stopped working. It no longer cut the engine but no fault codes. I saw this as quite good because the feature is a bit annoying in my opinion. However recently the car has started throwing up an amber warning light relating to the start/stop function. I’ve had the codes read and there was one for low battery voltage. It’s the original battery from 2011 and I’m assuming it will be this at fault, however concerned that it could be the alternator, and don’t want to waste £200. I’ve tried using a battery charger to boost the charge and this made no difference, suggesting battery fault to me.

    Any suggestions or advice? I’m guessing I could test the voltage when running to give an indication of output from the alternator?

    Thanks,

    Pete
     
  2. Postman
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    Postman

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    Not what one might call a very scientific or indeed specific answer but .... the daughter’s 116i amongst other problems after we bought it had a non functioning stop start. It was hinting every now and again that the battery had low voltage and indeed when the obdii was plugged in the voltage would initially show circa 14v then drop to under 12v (car running). I bought a new battery coded and registered it and stop start has worked since. On reflection the battery I replaced wasn’t an AGM @.@ so it wouldn’t have been up to the job most probably.
     
  3. PDoddy
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    PDoddy

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    Thank you for that. I tested the voltage when running and it was around 14.4V, which made me think the 9 year old battery was probably the issue. Have ordered one from Cotswold, so fingers crossed should sort it! When I was ordering it the chap explained that the health monitoring system shuts down various features as it detects the health of the condition of the battery deteriorating.
     
  4. a.s.uk
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    a.s.uk

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    How weird....
    A while ago a kind friend on here coded my stop/start to stay set in the last recorded selected position and not change...regardless of ignition on or off.... and it’s worked fine for several months..
    But just these last 2 days it started turning itself back to the stop / start position mid drive after each time I re select the continually idling position...?
    The time taken for it to switch back varies.... can be a few minutes to quite a long time....?
    What do you tech guys make of that...??


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  5. Wynne71
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    Wynne71 Site Supporter

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    I find it weird that my 2012 E92 doesn’t have stop/start. Maybe because it’s an auto?

    For the OP this looks like a case of battery state and charge. These don’t get checked on services by BMW, I think I may need to get mine looked at soon, suspect it is the original one.
     
  6. bishbosh
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    bishbosh WARLORD Site Supporter

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    @PDoddy a 9 year old battery is the most likely culprit. Don't forget the battery will need registering.

    @Wynne71 some earlier autos didn't have stop start. I don't think the zf6hp supported it. The zf8 does and this was introduced in the F series.

    @a.s.uk not sure what's happening there Al. I've not encountered the stop start setting changing by itself. Happy to take a look next time though (y)
     
  7. a.s.uk
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    a.s.uk

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    Cheers for info Dave...
    I’ll WhatsApp soon to arrange catch up..


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