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      11-10-2019, 05:26 PM   #1
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Drives: BMW E90 330D M Sport
Join Date: Apr 2017
Location: West Midlands

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E90 330D - Parasitic battery drain testing?

Hi All,

With the weather getting much colder I've noticed slower cranks but more importantly my battery is around 11.8v so a module probably isn't going to sleep properly (I have brand new alternator and battery already) so I was wondering how to do a check as mine doesn't have an IBS which I could have just used ISTA to put the car to sleep and check which module is drawing power. Do I just disconnect the negative battery and place my multimeter to positive battery terminal and chassis ground after putting the car to sleep with ISTA+ and any ideas what the correct draw should be when the car is fully asleep? I intend to pull fuses until it drops to the correct reading and then go from there
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      11-11-2019, 01:53 AM   #2
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Drives: E91 Lci, Vectra B V6
Join Date: Sep 2019
Location: Chester, South Wirral

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I'd start with the TCM.
Has your new battery been registered to the car?

You need to flick the doors and boot catch if you intend to work inside the car with it locked and asleep.

You connect your multimeter inline, so one probe on the battery post (either one) and the other one on the lug that you just took off the battery. Could easily be in the order of 5-10A at first but should drop to less than 50mA once its all asleep.
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