Hi, so for the past few months my Polo's battery has been going flat roughly every week. Having no knowledge about cars really, I just had the battery and alternator replaced, and the issue still occurred. Just lately, I've been really wanting to solve the issue, so I did some research, and tested the battery draw, and it's at a constant 0.11/0.12 amps while the car is asleep.

 

It is a 2013 Polo

 

After taking out fuse 23, it goes to 0.01/0.02, which is normal, apparently this fuse is for the ECU?

 

If anyone would know how I would go about fixing this I would be really appreciative. There is nothing plugged into the OBD port. Thanks.

 

The circled fuse on the left is the one causing the problem

Edited 10 June, 20242 yr by samster19
edit

There's probably more than one item fed from that fuse. Would need more specifics on the car to find out. VIN or reg plate ideally. PM if you'd rather not post publicly.

Pete this sounds very similar to the fault I had back in 2020,do you think it might be an idea to get samster to check the module under the dash for telltale burnt marks

This later model will have a different version of BCM, Mark, which isn't as straightforward to get into as the earlier ones.

It could be at fault though; as far as I can see, in the OP's car the only two items that fuse 23 feeds are the engine ECU (pin 73 of 121-pin connector) and the BCM (pin 39 of one of the two 73-pin connectors there, red/white wire).

 

Not sure how to work out which of the two is the problem other than disconnecting one at a time, but that seems a bit crude!

If I were a betting man, I'd put my money on the BCM, but it may well be something external to that which is causing it to not 'go to sleep' as it should.

Engine ECUs are usually incredibly reliable as long as they're not mounted somewhere vulnerable to flooding.