Electrical problems

[PeterAFox]

I don't really have the docs for this model, so all I can offer is a 'general procedure' with multi, mysterious faults which don't make much sense - it has worked for me occasionally, I do it progressively until I find the fault or my head explodes:

1) take photos of your fuse and relay boxes / locations first
2) Check EVERY fuse and relay, with a meter
2) use a blown fuse holder and insert alternatively into every fuse location, each time test each end for a voltage and a ground. Suspicious results need thinking about sometimes.

maybe it's trivial and doesn't bring anything, but it doesn't take as long to do as one imagines

[Josh282]

Hi, I’d be forever grateful if you could tell me how you sorted these problems I can’t find anyone who can sort them

[antcaddy]

Just had what appears to be same issues this morning. Did anyone manage to get to the bottom of their issues? @thecolourpurple @Irish-si @bozicek

[PJD]

Might be a waste of time but these days a bad battery can cause havoc with the most spurious of vehicle systems.

[antcaddy]

No issue with battery. Can activate the sensors and see the reverse switch is fine through vcds. @thecolourpurple @bozicek did you find out what caused it on yours? Seems like this is a common problem which is only gonna come up for others too

[antcaddy]

FIXED IT! Finally! BCM decided all by itself to change a load of it's coding. Only thing I ever changed in it a few years ago was LED number plate lights and mirror lowering. How random is that. I took a read of everything when I first got the van so was able to know what it should be coded with. If you have put a new BCM in you may have copied corrupted coding from the old unit

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[Larryd]

Happy days, shows the importance of backups!

When you installed the numberplate plate leds originally, did you have to code something to get them running correctly then?

[antcaddy]

Few years ago now so I'm not fully sure. They needed the coding to at least stop the warning light. Can't remember if they light up without as they were full modules not just a led bulb

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[Smales95]

Did you know what code was changed, I’ve got theses same issues?

[antcaddy]

@Smales95 have you ever done a vcds full scan of the modules? Like instead of doing a can gateway scan doing an old fashioned one. If you have it will be in there otherwise it's the time consuming way of using vcds and ticking the boxes which you think your caddy should have

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[STP]

Did you know what code was changed, I’ve got theses same issues?

Most likely area for these problems in the coding is "Central Electronics (09)" as this is the BCM really. It's where all lights/locks etc and controls / checks are coded.

What you can maybe do, as something similar happened to me, is get Obdeleven, don't buy the credits, just the pro version with unlimited long coding (£60 ish and a great tool anyway), connect to the adaptor, do a scan of control units, then go to that module from garage>module 09>long coding and press and hold on the green tick which is the same as "just do it" in VCDS, it should paste the default coding back again (or tick a couple of boxes for an innocent change like enabling auto door locking as per this screen and code it), then the BCM should get sent the coding and should fix the issue. You can undo the coding change later if you added something you don't actually want. Not much to lose if it's already not working.

[Sausage]

After having these same issues and spending a few hours checking fuses and bridging relays, I stumbled across this thread and thought no it can’t be.

Checked the coding with VCDS and compared to an older log and sure enough it was different.

Pasted the original coding and the heaters sprung back in to life.

Not sure how it’s been changed cause it hasn’t been plugged in for months, my van doesn’t get used a lot and was a bit slow starting like the battery was low, I wonder if this somehow confused the central electrics.

Big thanks to the poster anyway and I didn’t even think about the coding.

[jakemcc97]

Coincidentally did a load of reading on Central Electronics byte 18 today, it's the byte that controls the lighting scheme of the BCM and on a Caddy (at least on a MK4 Highline like mine) it's set to 00 (masked).

Loads of people have had pretty serious lighting issues by changing this, and changing it back to 00 doesn't revert the change, so sounds likely it could be the cause.

Not sure how it would affect the heater though.