Towbar electrics, Canbus plug removed without disconnecting battery, now have problems!

[Steve33]

I think I might have made a big mistake. Having fitted a towbar, and run the electrics cable around as needed, I was looking at where the connections are made to the canbus plug under the dash, and I took it out of its socket and then put it back in. I now realise I should probably have disconnected the battery first. A lot of the electrical functions seem not to be working. Dash display showing Brake fault. Engine won't start. Have I blown the control unit??

Advice very welcome.

Thanks

Steve

 

[Niknak]

Doubtful you’ve blown it, best suggestion is to check all your fuses first incase you spiked it, then if you can get it read with vcds and clear any faults and retry, I have seen bcms corrupted but even then can be saved fingers crossed it’s not that bad though

 

[Niknak]

But rule of thumb don’t touch anything control unit wise unless you have disconnected the battery

 

[Pauly]

I have done something similar and had some weird issues
I just disconnected battery for a while and everything was ok when reconnected

 

[Steve33]

Thanks Niknac and Pauly - sounds reassuring - I will go and disconnect the battery for a while and see it that sorts it.

 

[ei-aprilia]

I'd also double check you've got the plug back in properly too, it's in such an awkward place to get to you may have not got it back in correctly.

 

[Steve33]

I'd also double check you've got the plug back in properly too, it's in such an awkward place to get to you may have not got it back in correctly.

Good point - I will do that. Thanks

 

[Steve33]

Disconnecting the battery for a while and checking the plug have not produced any change unfortunately. Getting too dark to check the fuses ( and in any case, need to research where they are!).

 

[Steve33]

Update: have found a blown 25 amp fuse, and replaced this, but has not solved it - in fact whereas yesterday I was getting a dash display, today there is nothing. The only thing that seems to be live is the radio! I'll probably need to get my garage to look at it, but if anyone has any other advice, please let me know. Thanks

 

[Dellmassive]

Take a pic of your lower dash fuse box to compare.....

Maybe a fuse put back in wrong slot?

Or another blown fuse.

 

[huw169]

A mate of mine had a tow bar fitted couple of weeks ago by a well known independant in Cardiff.
Electrics went strange, independant couldn't sort it, got lifted to VW. They had it for 10 days and needed to fit a new control module, so i'm told.

Really hope yours is a better out come than my mates. Fortunately it was all free for him, but still a good while without the van.

 

[Niknak]

Double check your bcm pin connections and the fuse box connections for towbar

 

[Steve33]

Hi everyone. My garage had a look at it at the weekend. They made sure the Canbus plug was back in correctly and the pins were all straight, and that the fuses were in the correct slots, and all is now fine, so nothing too dramatic. They also connected the wiring to the looms under the dash, which they said was very stressful, so probably worth getting it in to them. I'm fortunate to have a very obliging garage!

Thanks for your advice, which I passed on to the garage as well.

 

[Flyingspanner]

Something may be worth looking at IF you removed both the black (T73a) and white (T73b) covers going to J519 (BCM) at the same time during the retrofit?
If so, make sure you have put the cover on the correct plug. The mechanical coding (only allowing the correct plug to fit into the ecu) is done with the outer cover ONLY!! If you get the wrong cover on the wrong plug, it will fit J519 but things won’t work and the heated front screen switch (if fitted) lights up as being on with the ignition off. Also the CAN bus wires will be in the wrong slot.
Took me a while to figure this out when a van was brought to me after someone retrofitted a tow bar as it looked correct and the plugs fitted as they should.
My advise is to ONLY fit wires into one plug at a time, then refit the cover before removing the other cover so as not to get them muddled up which is easy to do due to the limited space to work under there.
Also when removing and fitting fuses, it is very easy to fit the fuse in the wrong slot as they are not the easiest to see. With most group fuse boxes, they only populate the ones used (no spare wiring for other circuits for other options to save money), so have a look with a torch, any slots with terminals in both sides are usually missing a fuse, remove the fuse you just replaced, if it only has one side populated or non populated, you have fitted your new fuse in the wrong slot.
Good luck!

 

[saintclarkey1]

Slight change of subject but didn't want to spin up a new CanBus related thread. I was watching a video today where somebody was wiring a towbar into the canbus on a t5.1 Carravelle. I noticed the white and black connector block/wiring looms were facing into the cab rather than facing towards the engine bay. Seemed a lot easier for access but just got me wondering if this was a 5.1 thing or a Carravelle thing?