System reset following battery disconnect

[temeraire]

Hello,
Disconnected the battery a couple of weeks ago to fit new leisure battery and charger etc. Removed the drivers seat as part of that.

On reconnecting the battery a number of things work differently. The mirrors no longer fold on long press and the power tailgate which didn't open from the key fob does now. Also the ABS light has come on. I've just received a VCDS HEX-V2 to sort things out but before I start I just wanted to ask, is it normal for things to change if the battery is disconnected? Is it reverting to some sort of default config? Van is a 2018 MY.

 

[Loz]

Yes,
set the time in MFD>Settings
drive the window down manually, at the bottom, let go, press down again hold for 3 seconds
drive the window up to the top, let go, pull up again and hold for 3 seconds
repeat for other window.

 

[DanTK]

When VW Assist came out to sort my flat battery (effectively the same as disconnected) - once the engine was running the guy turned the steering wheel all the way to the left - waited for 3 secs, turned it all the way to the right - waited for 3 secs, and then returned to centre. This seemed to clear all the error lights on the dashboard. The mirrors seemed to correct themselves after a few drives.

Not sure how official or scientific this approach is but seemed work. Admittedly I’ve not had to do it since so not sure how reliable/repeatable it is.

 

[Loz]

When VW Assist came out to sort my flat battery (effectively the same as disconnected) - once the engine was running the guy turned the steering wheel all the way to the left - waited for 3 secs, turned it all the way to the right - waited for 3 secs, and then returned to centre. This seemed to clear all the error lights on the dashboard. The mirrors seemed to correct themselves after a few drives.

Not sure how official or scientific this approach is but seemed work. Admittedly I’ve not had to do it since so not sure how reliable/repeatable it is.

That is the calibration of the steering angle sensor.

 

[temeraire]

Yes,
set the time in MFD>Settings
drive the window down manually, at the bottom, let go, press down again hold for 3 seconds
drive the window up to the top, let go, pull up again and hold for 3 seconds
repeat for other window.

Perfect that sorted the mirrors. Many thanks.

 

[Rodent0_2]

Wonder if anyone can help please, just had the battery off our T6 California, (2017, 204, dsg, 4 mo), for a couple of days doing a suspension repair, reconnected it as per Autodata now have a load of issues, brake lights on continuously, engine management light flashes, alarm goes of every 10 mins, parking sensors not right indicates that a trailer is attached, gear box wont change up only manually, I have reset all faults with a Ross Tech VAG Com, driven it for just over 30 miles and still no good I would be grateful if anyone can throw any light on this or knows someone in the Derby area who would take a look please. Thanks. Anyone think that a faulty brake light switch would cause this as this is the only persistent error.

 

[Salty Spuds]

Wonder if anyone can help please, just had the battery off our T6 California, (2017, 204, dsg, 4 mo), for a couple of days doing a suspension repair, reconnected it as per Autodata now have a load of issues, brake lights on continuously, engine management light flashes, alarm goes of every 10 mins, parking sensors not right indicates that a trailer is attached, gear box wont change up only manually, I have reset all faults with a Ross Tech VAG Com, driven it for just over 30 miles and still no good I would be grateful if anyone can throw any light on this or knows someone in the Derby area who would take a look please. Thanks.

Dunno if this helps or not, but:- I’ve just changed the battery on my van & had a few faults on when I reconnected the new battery. Not as many as you, traction control, bulb failure, abs. I plugged in VCDS, did a scan & hit the reset all DTC button. VCDS did its stuff but the faults were still there. I had to go into each individual module & clear the faults one by one, all good now.

 

[Rodent0_2]

Thanks for the info, done it both ways several times, ignition on/off, engine running you name it, just one fault reappears that is a brake light switch and as the lights are on maybe a possibility, tried disconnecting it and the lights stayed on but that probably as its electronic not physical. Its all very odd and bonkers as you can't change/disconnect a battery without all this hassle, there were no issues with the van when I started other than a damaged top suspension bearing and its only done 50K.

 

[Salty Spuds]

Thanks for the info, done it both ways several times, ignition on/off, engine running you name it, just one fault reappears that is a brake light switch and as the lights are on maybe a possibility, tried disconnecting it and the lights stayed on but that probably as its electronic not physical. Its all very odd and bonkers as you can't change/disconnect a battery without all this hassle, there were no issues with the van when I started other than a damaged top suspension bearing and its only done 50K.

VCDS needs ignition on, but engine not running. Is it a genuine VCDS cable & is your software up to date?

 

[Rodent0_2]

Yes all genuine, and soft and firmware up to date. Thanks.

 

[Salty Spuds]

Yes all genuine, and soft and firmware up to date. Thanks.

Have you got a VCDS scan? It maybe that during the repairs (why did you disconnect the battery for a suspension repair?) you’ve actually acquired a genuine fault(s), possibly a trapped or damaged cable or a loose plug somewhere.
You could also try the capacitive discharge reset trick, as counter intuitive as it may sound, disconnecting the battery & resetting the system “might” help.

 

[Rodent0_2]

Had to remove the battery to get at the nearside suspension top in order to remove the strut. no cables trapped, did disconnect it again Tuesday night in order to lock the vehicle as the alarm was going off, didn't touch it yesterday so reconnected today and now struggling.

I can get a scan and upload it, hadn't saved todays.

 

[Gavinda]

@Dav-Tec isn't too far from you. He knows his stuff with the electronics on these vans.

 

[Rodent0_2]

latest scan

 

[Phil_j89]

The brake light switch is on the master cylinder, check its located properly. They can be knocked quite easily, which would give similar symptoms to what your experiencing.

Do you have a tow bar fitted? Showing no communication with towing control unit and single single wire can mode. May be worth checking you've not moved any wiring / disconnected the tow bar control unit, without realising.
You could remove the trailer from 19 Databus fitted control units using VCDS and see if this changes the faults.

 

[Rodent0_2]

I've ordered a new switch, just in case and to eliminate it, haven't really been under that side of the bonnet to knock it, I did disconnect it but made no difference. Yes does have a towbar, I'm under the impression and stand to be corrected I noticed on earlier scans that you don't get comms until a trailer is plugged in ? I can check that..yes thought about removing the module and trying I, there are around 6 wires and a fuse box which were added for the towbar along with the module all these wires are tied down to the the pos terminal of the battery. Two of these (mainly white) came off the, I'm fairly sure the pos clamp with the others, whoever fitted it cut the eye lugs and turned them into spade lugs, I'm sure the neg battery clamp only has the voltage sensor thing on it, these other two wires couldn't have been on the neg side as they would have to have been bent to make them fit. could do with a wiring diagram for the module.

 

[Pauly]

I would say its highly likely all these faults are related and the root cause is the towbar module/wiring

The module should be present at all times regardless of a trailer being connected or not, the only way for a control module to totally disappear would be if you interrupt the canbus connections or the power supply to it. If its been hotwired directly to the battery then i would defo start by double checking there, fixing that will almost certainly clear the PDC error just a question mark over the brake switch ?

Perhaps some photos of the battery connetions if your not sure

 

[Rodent0_2]

Just had this from the guy who did the towbar stuff


"""Hi Nick.

The four white cables should from memory goto battery earth… (one of them should have a red stripe and another a black) if thats the case definitely battery earth.

The module only runs the trailer lights and shouldn't have any significant effects on the other systems/ faults you've described . On VCDS with the white cables disconnected it should show the Trailer addres 69 (being unreachable)... if that's the case, reconnecting the cables should bring the module back online.

I do think from experience the faults you describe are not the fault of the trailer module ... proof of which should be when this is disconnected it rules out a short on the canbus system..."""

Looks like have them connected wrong. !!

 

[jimc91]

I don’t think anything should go to the battery earth on these vehicles as it conflicts with how the battery monitor functions

 

[Rodent0_2]