Hello, battery draws can be very difficult on more modern vehicles with the endless amount of modules present now. Looking over our service info here in the US, its showing Fuse 16 in the engine compartment (under the bonnet) is not used of course, so maybe we can go about this a different way. When you do your testing are you fully putting the vehicle to sleep, (ie, latching all the doors when open, the hood latch, trunk latch, any place where you need to access fuse panels), and then locking all the doors and giving the vehicle a good amount of time to power down the communications networks? Thats going to be the first step, since some vehicles can take quite a while to go to sleep.
And without pulling any fuses, I would try the voltage drop method of checking for any current flow across fuses. Not sure if you are familiar with this method or not, if not just let us know, and it can be explained further. Also do you have access to an oscilloscope to actually watch the networks power down?
There have been some really crazy case studies where a module might be trigger to wake up only after a certain period of time, then might go back to sleep, just to be woken up again by something on the network (data bus) triggering a wake up signal. 400ma is too much of a draw for sure, with that much current flow you should be able to find a fuse on the interior panels with some voltage drop on it. It wont be much, but each fuse should be 0.0mv. The only Back-Up fuse I see in our service info is for the reverse lamps and that is probably not the type of back up fuse we're thinking here.
So make sure you have the vehicle fully asleep and all doors latched/locked. Give the vehicle an hour and see if you read any voltage drop on fuses in the interior panels. I would even go so far as to check switches/latches with a scan tool, checking the body control module or ECM to see if any are reporting to be On or Open, even when they are closed. Latches fail just like everything else. Any codes setting after a couple key cycles? Dont write anything off just because it may not seem to be related and if possible see if any repairs have been done recently where aftermarket parts may have been installed. The parts we are seeing now is really getting to be a problem, with many fake parts being sold on amazon or elsewhere. Check these things if you havent already and let us know what you find or have found.
https://www.2carpros.com/articles/car-battery-dead-overnight
Monday, August 25th, 2025 AT 8:18 AM