Van won't start - Several comm errors [RESOLVED]

[SW_Mus]

So yesterday I decided to check the fuses for the heated screen as one half stopped working a couple of weeks ago. Quickly found the fuse, and it had melted! I noticed that the the fuse holder was very dirty/corroded and wobbly, and that the box cover hadn't been closed properly by the last person in there. For info, I've had the van (2018 150 DSG 49k miles) since April 2022 and have never had cause to go into this fuse box before. Realised that the holder will need replacing but decided that it was a job for another day. Closed everything up and then when I came to start the van had it loads of errors, and the van won't start! The display tells me to select park, which it already is, and press the brake, which I am. Stereo said something about park assist as well.

Carista report is attached.

Presumably in checking the fuses I had dislodged something and ended up breaking a connection somewhere. I assumed the corrosion meant something wasn't fully seated/bonded under the fuse holder. So today I have removed the battery to gain access to the wiring beneath, and quickly realised that at some point someone has spliced into the loom, and there are lots of suspect connections. Prime candidate is something to do with transmission ECU. Not quite sure where to start to be honest...

 

[Dellmassive]

That front fuse box looks terrible. And will need replacing id imagine.

Looks like salt water got in there?

 

[SW_Mus]

Yeah it's really battered. Several bits broken off it, and the retainer clip/spacer that stops it rattling about was missing too. Not sure what happened exactly, but yes it does look like salt corrosion. I will replace the fuse holder at some point, but right now I'm trying to just get the damn thing running again! Some of this wiring is really dodgy. Looks like a cowboy has had his hands on it in the past.

Is this the ECU that lives below the headlight? It has a zip tie around one of the connectors holding it in, and every wire from that plug is spliced into the loom.

 

[Pauly]

That all looks pretty normal to me
Was is just the front fusebox missing the cover or the whole ebox ?

 

[Pauly]

Heres the plastic part that holds the terminals in place

 

[Pauly]

The load side cable of each fuse slot would be ok to repair as the corroded crimp can be cut off and replaced
The fun bit is going to be the supply rail that runs down the feed side of the fuse slots, its part of the wiring loom and could be tricky
IIRC the rail does clip in and out of the fusebox so i guess you could buy a 2nd hand loom or fusebox and cut/join the rail to your existing feed cable if needs be, i guess you wont know the extent until you get it out and have a proper look ??

 

[Pauly]

Found these matching part numbers on ebay at the moment

Pardon our interruption...

Pardon our interruption...

 

[SW_Mus]

That all looks pretty normal to me
Was is just the front fusebox missing the cover or the whole ebox ?

Fuseebox cover was fitted, just not closed. I’ve taken the main cover off this morning to try and see if anything was obviously damaged.

 

[Pauly]

While its off i would check all the fuses in the primary fusebox under the battery and make sure nothing is blown there, then use a multi meter to check for 12 power on each of the fuses in the front fusebox, there is a small piece of exposed metal on each side of the fuse on top for this purpose

You should be able to figure out if you have a lost one circuit or a row of circuits then start to narrow down your issues

 

[SW_Mus]

Yeah I verified all the main fuses under the battery. All the fuses in the SB box seem fine too. I need to put the battery back in to make sure I am seeing 12v at each of them. There's a few dodgy looking splices which I am in the process of redoing, and at least one wire that looks to have been trapped at some point. Going to have to put a new splice in that too so that I can make sure it's not broken.

I'm confused as to why part of the loom has been spliced though. Could that be to swap out the ECU for another vehicle of a different spec? Or maybe it has suffered some crash damage I wasn't aware of. Pretty sure the front bumper was replaced by a previous owner as it has washer jets and a radar unit, neither of which appear to be functional.

 

[Pauly]

All vehicles have radar for front brake assist even if you dont have adaptive cruise
Washer jets is standard with LED headlights and only activate periodically (think its every 10 windscreen washes but not 100% on that)

 

[SW_Mus]

Thankfully I've just managed to fix it. It was one of the many (very badly spliced!) wires from the ECU connector that had been pinched in between two bits of broken plastic. Wasn't fully severed but looked like it might be dodgy. Pretty happy right now. Your guidance is very much appreciated.

I do still need to replace the fuse holder at some point to sort the heated screen fuse, but that can wait to another day.

 

[SW_Mus]

All vehicles have radar for front brake assist even if you dont have adaptive cruise
Washer jets is standard with LED headlights and only activate periodically (think its every 10 windscreen washes but not 100% on that)

Ah didn't know that about the radar. I wish I did have LED lights. Bog standard candles only unfortunately.

 

[mmi]

Hmmm, a couple of UK members are left without the radar

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