nw83

Thanks for the info and help. I understood most of it. I took the cover off the rear light and immediately I could see the wiring was different to your diagrams so I didn't actually go any further as it must all be can bus type data signals now which I don't really know how to check anyway. Its just got 3 wires going into the light. Brown Black / White Purple / Brown or Yellow.. couldn't quite tell. So... short of still hoping that an error code reset will fix this... I'm stumped and it will have to go to the dealers.

@dv52 further to this... a couple of new developments. I checked the CCTV from last week when the car was outside getting washed following the tracker installation and before the detailing. the brake lights were working normally. Also... to rule out any crossed earth etc, I disconnected the tracker and immobiliser this eve. The rear passenger light still had the fault (although thinking about it now perhaps I should have also then disconnected the battery earth for a few mins to reset everything and THEN see if the light behaved itself?) Even though I feel its un likely I caused this with the wiring... I don't like just giving cars back to customers with issues. Do you think it would be beneficial to get to the plug on that light and check the power and earths are getting through properly. If they are... surely that means an internal fault in the actual lamp? If not... still a potential wiring issue somewhere? This is a 2025 car with the IQ lights. I don't suppose you have a wiring diagram for these? Also.. just to clarify.. the issue I'm having is that when you unlock the car and turn the ignition on the light behaves normally as pictured. As soon as you press the brake pedal to start the car, you get the error on the dash 'check rear left light' 'rear left brake light fault' (or very similar wording to that effect). And when I'm standing looking at the rear lamp when someone pressed the brake, the brake lamp part doesn't come on (high level lamp and drivers brake lamp come on fine) and the outer LED part then partly goes out. The rest of the light functions fine. Indicators still flash and the side light / running light still stays on. Also just to double check.. the lower brake light part lights up (but dimly as you see in the pics here)... not bright like when the brake is applied) when I walk up to the car with the key. Is that normal?

Appreciate this and don't worry, no offence received. For clarity.. are we talking about the thin black module that is next to the fuse box behind the glove box? With 3 large plugs in it? (typically I'd recognise this as the body control module on other cars) If so, the tracker is not wired in there and I didn't go near that module and actually, it looks like the fuse board needs to come out to even get to the plugs so while I'm happy to do more work and try to check it, it looks more destructive to try to take it out.

Seeing as people helped me.. my bit of 'giving back'. The golf R I worked on had solar reflective glass and as such the tracker module didn't get a good reception when it was installed int he cabin. Ended up relocating to somewhere 'not in the cabin'

Ok thank you .. Well at least I know that now and I wont waste any more time with the dongle.

Yes the drivers side seems to operate perfectly (and no dash error warnings) Just the passenger side that has no brake light, and this outer surround light is intermittent

this is the rear light when its not fully illuminating. See the side and lower part of the outer surround is not lit up. But then other times it does light up.. like when unlocking the car for instance.

OK to the VIN. Sometimes when you click on the 'control units' icon it lists out all the units I expect to see when connecting to a car. Body Control, Central Electrics, ABS, AirCon.. etc. But it wont let me connect to any of them. I get the error "control unit not responding. Check ignition and try again" Other times it only shows the Gateway module (19). It lets me connect to that and says it has some faults, which I've googled and one is to do with the rear cam (which works fine... and the google consensus is to ignore it).. the others seemed non relevant to this issue and again generic ones which most people say are always there and to ignore. If I try to clear them it says its succeeded but they come straight back. I actually took the dash apart again this evening to make sure I hadn't missed something and everything is plugged in as it should be. I didn't go near the BCM or unplug anything other than the air bag switch on the side of the dash and the button cluster with the hazard switch which you have to unplug to get that trim out so you can remove the glove box. Sorry for not being clearer.. its been a long few days on various projects and im trying to problem solve this one late in the evenings and I'm not familiar with the obd11 software yet. Small point.. the car has also been detailed while it's been here... washed and lots of machine polishing. Is there a chance the actual light cluster has failed somehow (water ingress or vibration) and its not a stubborn fault at all but a failed cluster? Symptom is that it seems to function fine.. indicator works, side light works but no brake light on the left / passenger rear cluster. Also the glowing outer section only part illuminates sometimes.. but other times it lights up perfectly.

greatly appreciated. This thread on obd11 forum best describes what I experienced. https://forum.obdeleven.com/thread/35127/control-unit-responding

I tried multiple times and yes to both (although I'll try again again tomorrow). Also... I've been working with cars for 20 years and I don't THINK I'm an idiot... but there is every possibility that I have missed something so thank you for the advice... even if its simple things. Out of interest should I be using the 'for vag' app or the normal one? For some reason the normal one wont connect to the dongle now (says my 6 digit pin is incorrect)... but the 'for vag' app connects just fine and lets me change the pin so not sure what's going on with the normal app?

ok thanks. Any idea why I cannot connect then? I’m getting conflicting info. Obd11 forum says it’s locked as it’s SFD2. but you guys seem to think I should be able to connect and clear any codes?

Tried with ign on and car running. No difference. using iPhone 15

Hi. Sorry.. new here.. Got a 2025 golf with a few faults after a tracker install (owner also on here and knows about them) I've bought an obdeleven next gen device, set up my account, confirmed email, set up google 2 factor, got the bonnet open. I'm using the 'for vag' app as the other one keeps getting in a cycle of telling me my authentication is good and then asking me to re connect. The 'for vag' app seems to connect but takes FOREVER to search for installed modules and then tells me there arent any other than the gateway module? is this normal? Any help greatly appreciated before I accept defeat and pay for it to go back to a dealer