Xc90 ABL - One has Error Code

[benjyman86]

Hello,

Very new to this forum, but found this thread and wanted to mention that in my XC90 First Edition D5 I have had the same fault. As I live in Sweden I have been fiddling around this for years now. The first light gave fault and did not operate at around 125 000 km and I managed to get a used one from local dismantling place (driven 5000km) which now have started to act up again. Now the car has 230tkm. So it seems that they last about 100tkm.
Since I kept the old light with me I teared it apart completely to see how the interiors look like and much to my testing I could not find any issues, but I can post here loads of pictures from these internal parts and maybe someone with good electronic skills can give some hints.
There is a 4 different led modules each of which has quite serius cooling fins, but only under 1 (daylight element) there is actual cooling fan. Now here in volvoservice the guys told me that some people have added extra fan and that has worked so I am exploring this at the moment.
Another item I noticed that there is the ventilation mesh at the backside of the light which does not really seem to let air through so I am planning to change that to a different material to see if it makes any difference.
Also what I noticed there are internal screws that allows you to swivel approx 4mm the daylight module inside (though the access is quite bad) which gives a bit more space between the fan and heat sink.
As I will start dealing with this now thwn probably I will add some information here in the future if you like.
Let me know if pictures are welcome from the interior of the light and I will try to figure out how to post them.
Also worth mentioning that this issue will not be fixed by changing any of the external modules since it is some internal heat calculation or chip that gives the error. 
I could not find such resistor but maybe you guys would be able to tell how it should look like.
I will be able to take some pics next week so hopefully it might help.

This is great and I found by trial and error that the modules like you say don't actually alter the reference that it gives back to the CEM. I had been at a bit of a stuck point until I can get a used unit like you did. It would be good to understand if there's a 'fix' that can be adapted for the temperature, but I would imagine it is a resistor (thermistor?) that has burnt out isn't it? I say that as it will immediately trigger on my one. It intermittently will work, sometimes I can go multiple drives and it works, then I get nothing for a week or 2, then it's back and then I can go for a drive to the shops and it doesn't work, but driving home it does. Very odd where it will intermittently pass it's own tests. I have found some electrical experts locally but none of them would touch it as they don't think that they could save it due to lack of knowledge of the wiring and schematics so the effort vs benefit wasn't worth it for them frustratingly. I haven't got a spare for me to strip it down either anyway. I did do electronics at college but that was many, many years ago!

So I'd be interested to see what the internals look like, the error code is supposedly due to temperature like you say, but I am not entirely sure which circuit that would be or if cooling after it has already got to this point will help, but would be interested to see?!

Thanks

Ben

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