Removing Fuse 23

[davemap]

Hi, I have a polo 6r 2011 1.4 petrol and when i leave it on the drive for more than 3 days, escpeially when its cold, the car battery will go flat and the car wont start. I have checked the current draw and it seems when off, there is 200 mA being drawn. I went through and removed fuses until i got to fuse 23 and the current dropped to 50mA. Looking online there are a few things this fuse is connected to but I have no idea where to start. Has anyone got any advice or ideas? Thanks in advance

fuse 23.PNG (6.29 KiB) Viewed 4981 times

[veteran]

According to my reckoning, the battery will have drained down by 14.4 AHrs in that period, which is a fair old percentage and may well be enough for a battery that's been in use for a year or two to fail to turn over the engine well enough to get it started, especially in cold conditions. The current draw you've measured is possibly indicative, on a car of that type and year, of the total that gets drawn by onboard devices such as the alarm system and several other parts of engine and system management when the ignition's fully off and the car locked and armed, though in a newer Polo 6R, ie. a 6C, I'd hope that VW's brought that down to 50mA or less. I agree, though, that when you then try to fathom out whether and where you could afford to lessen the current draw, the documentation's woefully wanting. Fear not, though, as I'm sure there are experts in these forums who'll be able to help you (sadly, I'm not one of them).

[RUM4MO]

This sort of thing is a bit tricky to work out what is going wrong. In case you do not know, the Body Control Module, or BCM which is circuit reference j519, controls the shutting down of power to all areas were it is not needed when the car's engine has been switched off for some time, so, in an ideal world your car should survive at least 6 weeks before the battery has dropped too far to be able to start it.

Two options only for why this is happening, firstly there is a fault in that car which is wakening up the management comms and so all the power supplies, the other option is that the BCM in that car really does need a software update due to it currently having been coded at the BCM factory wrongly.

Now you may be thinking that that can not be possible as that car worked okay in the past - wrong, it could be that your battery has degraded and so is reaching the "no go" sooner than it did in the past, coupled by the winter low temperatures, and so that software issue has always been there in the background - or the way that you are using that car has changed and so caused this issue to give you problems.

If it is just the BCM S/W problem, and that problem is known to VW Group dealers, but most will have been sorted out many years ago as it only concerned a certain build date of BCM and so cars, Polo and Ibiza - so if you try to get a VW dealer to sort this out they will now not remember much about this issue nor will their locally held data base of unusual faults.

My older daughter's late 2009 Ibiza had that issue, I messed about with it for about a year while she was working abroad, I could not find anything at fault with that car so I handed it in to a SEAT dealer, I reminded them that it could be just a BCM S/W issue which was known about and that car was within the production batch that could have had that issue, this was dismissed as just internet chatter, I was charged for an hour's diagnostic time with their master tech who quickly discovered that the unit under the steering wheel that enables the front fogs as additional lighting when turning slowly was faulty, so they replaced it and recoded it etc, that cost me well over £300 and even as I walked out the door I was questioning this fix! Car seemed to be okay for about a month, though it could have been down to usage etc, then things went back to being bad and the battery was discharging, I handed it back in and they kept an eye on it for a week and in all that time they claimed it was fault free, I took it back, and soon discovered that it was not okay - I worked this out by not using it and connecting a fused long monitoring lead from the battery terminal to outside of the car and logging battery voltage. Then I received notice that the local motoring group were closing this SEAT garage, I went and chatted to them and they said not to worry as we were good customers of SEAT, SEAT UK would support us in solving this on going problem. Some time later I bought a CTEK battery tester and found that the battery was not quite as fit as it could be, car was 7 or 8 years old by then, so replaced the battery with an identical but better grade one. Still monitoring the battery voltage and leaving the car out of use - still draining the battery though as you would expect, it was taking longer.
Time for action as my daughter was returning to UK for the festive period as she would need to use her car for maybe 12 days - so I booked it into another SEAT dealership and right away the service reception guy said "it could be the BCM S/W we have just sorted out a Polo with that issue" - so things looked good, car was handed in and they went through the usual primary diagnostic checks, found no faults with the car, checked for updates and found none and so the tech initiated the next step given the back ground to what had been done so far to that car, and that was to log a help request on SEAT's or VW Group global tech resource and I was told that they would get a reply within 48 working hours. A few days later I called in and asked for an update and yes they had been given an answer and the code of the old S/W patch that that car probably needed, things started to look good, car was booked in for after my daughter left UK, S/W patch or update applied, problem gone!

Edit:- as far as I could make out, VW Group do not hold any records of if or when these updates are applied and by connecting to the cars they can't work out if a patch or update is needed, even after they apply the patch or update they can not see if it has been applied - it is just down to "did the problem disappear?"

So, I think that you really do need to get along to your nearest VW dealership and spill your story, maybe including the possibility that it is just a BCM ie j519 S/W issue, you will need to pay for a primary diagnostic check, then the actual time for a tech to apply the update or patch, the S/W update itself is free, good luck!

Another Edit:- the actual software patch/update/code was listed as 30EB , if that helps at all.

[RUM4MO]

Just an idea of what charges you should expect, based on prices from December 2016 and January 2017, initial diagnosis cost me £99 inc VAT, applying the software patch cost £61.40 inc VAT

In the bigger picture, not a huge price to pay for being able to leave that car for a few days and jump into knowing that it will start.

For any/many reasons this seemed to only be an issue with cars that were fitted with the 1.4 16V 86PS engine - which is probably more a trim/equipment level thing, ie being fitted with the "low" version of the BCM.

Edit:- just one small thing, if you monitor the battery voltage, you will see that it is lower for as long as the BCM is holding the unnecessary power supplies on, as soon as these supplies get shut down the battery voltage will recover for as long as the power supplies or held off, quite obvious when you think about.

What annoyed or confused me was that when I spent a bit of time looking at things, it seemed to stop this nonsense I'd start believing that all was now well, only to get a bit annoyed a few days later, so that was when I started connecting the monitoring lead up every time I stopped the car on our driveway!

Another Edit:- actually checking my records for that car, this battery draining issue started or was first found by me on 14/12/14 and was finally put to bed on 5/01/17 though that car was not essential for us to use as we have our own 2 cars, but it does show just how long things can take when you ask main dealers for advice about updates and get brushed aside!

[RUM4MO]

Hi, I have a polo 6r 2011 1.4 petrol and when i leave it on the drive for more than 3 days, escpeially when its cold, the car battery will go flat and the car wont start. I have checked the current draw and it seems when off, there is 200 mA being drawn. I went through and removed fuses until i got to fuse 23 and the current dropped to 50mA. Looking online there are a few things this fuse is connected to but I have no idea where to start. Has anyone got any advice or ideas? Thanks in advance
fuse 23.PNG

The item listed as Onboard supply control unit, is in fact the BCM which does the controlling/switching of many functions and so knocking that one out will always stop this issue at source.

[iichel]

Is your car equipped with any of the other devices listed, such as the rain and light sensor?

[davemap]

Thank you very much for everyone's responses. I am definitely going to see if I can get this software update done as I hope that fixes the problem. I dont have the light sensor or the rain sensor so I can rule those out and I dont have a start-stop model so I can rule out the data bus thing. I continued pulling fuses out and found that with fuse 23 in, removing 52,51 and 50 reduced the current to 100mA. Im going to have a look at what these fuses are connected to but it definatley seems that fuse 23 and most likely the BCM is the problem. Thanks once again for all responses

[RUM4MO]

At a guess, without looking it up, the first fuse that you have removed is the BCM's management supply fuse, its outputs that it supplies and or switches, will also be fused by other fuses, so combinations of fuse removal will reduce the current drain, but the first one seems or should kill all the switched supplies as the switching control function has been taken away. I'd still think that you will have an active data bus with or without Start/Stop being fitted to that car.

Edit:- in case that you are mildly interested and I'm sure that you don't really need to be, it becomes quite tricky to work out what is happening by just pull out fuses as you are probably wakening up previously shut down supplies. The official way to do this seems to be to monitor milli volts readings across fuses!

I found just pulling groups of fuses gets you confused unless you keep a log on what you have taken out and the response in terms of current drain - after 30 minutes or more - and more often ends up with you disproving any clever ideas that you have worked out about what the root cause of this problem is.

Diagnostic check by proper VW workshop while hinting that you have looked around and think that it might be due to incorrect coding of the BCM, ie j519 - and if they don't want to work to your instruction, formally request that they get a tech to log a request for info to the greater VW world. This can be done, it happened to me and I'm not just spinning a bit of internet chatter, so do press them as all this seems to have been forgotten about and all "legacy" fixes have vanished off the dealer's online diagnostic "fact bank".

[davemap]

At a guess, without looking it up, the first fuse that you have removed is the BCM's management supply fuse, its outputs that it supplies and or switches, will also be fused by other fuses, so combinations of fuse removal will reduce the current drain, but the first one seems or should kill all the switched supplies as the switching control function has been taken away. I'd still think that you will have an active data bus with or without Start/Stop being fitted to that car.

I think you might be right. It was only that I went on another site and it looked like it was only applicable for start/stop cars. Is the BCM update the same as the ECU update - sorry for silly questions, im new to all of this.
Thanks again

[RUM4MO]

No, and I've edited my last posting after you posted your last one.

The BCM hides up above the pedals area.

If you are new to all this, this is potentially a horrible fault to try to sort out as your first one!

[Dink]

How long after switching off the car did you measure the current draw?

As there maybe a delay in switching certain devices.

I'd be getting the battery checked as lead acid batteries can take a small load like that for longer than the capacity would imply.

[davemap]

I checked the current after about a minute or so as the clock display and all the other systems have turned off. I got a new battery today and all the reading ive taken have been done after changing the battery.

[RUM4MO]

There absolutely is a delay in the shut down sequence that is why I mentioned the 30 minutes, but that does not explain the habitual battery draining after 3 days, that must be due to either a fault or the going to sleep procedure being interrupted - which is normally due to a BCM S/W issue, for anyone that has not suffered this, this sort of issue might not be a typical problem, but for the relatively few that have come up against this, it is a real issue, quite a few people have quietly sold/traded in their cars to escape from this issue as most "fixers" have either not heard about it or are not willing to fight to get access to the BCM S/W update coding from VW, including too many VW Group dealer's workshops, not a quick parts swopping task so not interested in it!

[RUM4MO]

I checked the current after about a minute or so as the clock display and all the other systems have turned off. I got a new battery today and all the reading ive taken have been done after changing the battery.

You must wait roughly 30 minutes if you are wanting to record what should be the "systems shut down" steady current, then again another roughly 30 minutes if you have wakened systems up by opening any closed doors or removed/replaced any fuses.

[FlyingSpanner]

I have just updated J519 for this issue. Factory technical bulletin to update word 09 (J519 or body control module) due to alarm circuit not shutting down correctly, the battery may discharge after 3 days standing.
Req software update to rectify.
The one I’ve just done was a 59 plate 6R with Part number 6R0 937 087 B software version 0025, update version is 0029.
Book it into your dealer to get it updated or your specialist if they pay for ODIS access.