Parasitic Battery Drain E85 Z4 2.0

J

jambojambo

Member
I've got an issue on my E85 Z4 2.0 where if it's not used for a couple of days the battery dies and is completely flat to the point there's no electrics whatsoever. I'm keeping it on the Ctek now but need to get the root of the issue.

Some bits that may or may not be useful to diagnose:

- The key in the door no longer locks the central locking, although central locking does work when pressing the interior button by the hazard warning switch.
- The key remote doesn't ever close the doors but can on occasion open them and the boot. (may just need a replacement fob battery)
- All of the interior fans seem to be working fine at all stages. I read the FSR can be an issue but I can't hear any fans over running etc.
- Alternator doesn't feel warm after being left, so no major signs of a reversed diode.

I have ISTA and INPA if that can help with diagnosis. Does anyone have any good ideas/clue to help me diagnose this?
 
Sounds like the GM5 is on the fritz whatever but I've not heard of it drawing excess current. Is the battery in good nick generally?

For diagnosis, you don't want ISTA, you want an ammeter to measure the current draw when it's nominally asleep.
 
Thanks for that, do you think it's worth getting the GM5 looked at then? The battery is in good nick and I put another fairly new on I had from another project BMW and it did the same to that one too. I was wondering if it's not going to sleep. It seems on average to take something between 24-48hrs to completely flatten the battery
 
Probably not the same but I had a few issues with the alarm and battery drain. For me it was the bonnet sensor and apparently the petrol cap sensor. Though I never quite worked out how, after I was told that by the tech. I never saw the issues again.
 
To be thorough I agree with @smorris_12

With ign off measure the drain on the battery with ammeter

If it’s high (I can’t recall the resting amperage) then start pulling fuses one by one to identify the circuit with the issue
 
Lock the boot latch by pushing it in with a screwdriver. That way the car will think it's all locked up, otherwise it's still waiting for the boot to close to arm the alarm and running the 20 minute lights timer.
 
Excellent tip cheers for that. So at the moment I think the GM5 is defective as when I lock the car it doesn’t activate central locking so I’m having to manually lock each door. Will that affect the sleep time do you think?
 
It's possible that's just relay problems but it might be more fundamental. Pulling the fuses or disconnecting it and leaving for a few days would tell you which.
 
OK I pinned it down to two things, the GM5 Star 12 Low wasn't letting the car go to sleep. It was stuck at 0.35A draw. The radio was also pulling 0.75A so that must be faulty too. Now i'm down to between 0.02A and 0.05A. Thanks for all the assistance!
 
Interesting! I've just ordered a used Star12 High out of an E46 with matching SW and HW so i'll code that in NCSExpert once it turns up. The GM5 was already looking like it was on the blink as I'd lost central locking a few months ago and it only worked off the interior switch and not from the door locks.

I first discovered the radio was pulling a parasitic draw, removed the fuse and it dropped significantly. Then tried a load of other fuses which didn't do anything at all. Then disconnected the GM5 and a few minutes later it was down at 0.02A.
 
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