DRL not working after fitting LED bulbs [Solved]

[Pete24]

Hi all,

We have a 2015 T5.1 and a few months ago I fitted some LED bulbs to the DRLs and side lights - they must have been cheap crap as they have given me a couple of issues.

First off, one of the side light bulbs failed (as did the same bulbs in the rear number plate light!), so I have just re-fitted the original filament bulbs.

However, something a bit more serious has happened with the offside DRL. For some reason it has stopped working, and I know it is not the bulb at fault as the same bulb works fine when swapped to the other side, although I get the feeling the bulb has caused the fault! A standard bulb worked just fine for the first 5 years of its life, but within 100miles of fitting the LED bulb this happens. So something else is at fault. I was just wondering if anyone could shed any light on the issue before I spend money on an electrician to sort it out? Any common faults I can look at? Any hypotheses as to what might have happened?

TYIA

 

[Pauly]

DRLs are sometimes connected backwards at the factory ie reverse polarity
A standard lamp wont care but when you fit an LED lamp which is polarity conscious it wont work until you swap the wires around in the lamp holder

If LEDs have worked in there and now the standard lamps wont then its possible the van logged an error with the LED lamp and shut it down, if this is the case then there will be fault code(s) and may need to be reset to get it operational again ?

 

[Pete24]

Hi Pauly,

Thanks for the suggestions. Are saying the two issues are linked (polarity & error code)? I.e. the reverse polarity would have had the LED working initially, but after a while this caused the error? This would explain why it was working when first fitted.

If this is the case, would I need to swap the wires and then get the fault code cleared?

 

[Pauly]

No they are just two issues i am aware of, if they used to work then you dont have the polarity issue, your van may just need fault codes resetting then ?

 

[Pete24]

No they are just two issues i am aware of, if they used to work then you dont have the polarity issue, your van may just need fault codes resetting then ?

Ok thanks. Is there a cheap way I can do this at home? Some sort of diagnostics reader I can search for? Or is it a trip to VW? I also have a mk7 Golf, so if there is such a thing that would do the job on both vehicles that would be very handy

 

[Insert Coin]

Carista will read codes and reset them for you and will work on the Golf too.

 

[Pete24]

Carista will read codes and reset them for you and will work on the Golf too.

Thank you! Much appreciated

 

[Pete24]

If LEDs have worked in there and now the standard lamps wont then its possible the van logged an error with the LED lamp and shut it down, if this is the case then there will be fault code(s) and may need to be reset to get it operational again ?

Pauly, do you know if this is likely to be a lasting solution, or will the same error keep cropping up and need resetting?

 

[Pauly]

Who knows ??
Depends if that is the issue and what caused it

 

[Robert]

I would suggest to clear faults in 09 BCM
and then untick Bit 2 in Byte 16.

Additionally DRLs have common GND with side lights, low beam, high beam & indicator so it is quite impossible to have reversed polarity on any of these.

 

[Pete24]

I would suggest to clear faults in 09 BCM
and then untick Bit 2 in Byte 16.

Additionally DRLs have common GND with side lights, low beam, high beam & indicator so it is quite impossible to have reversed polarity on any of these.

Not sure what 09 BCM or Bit 2 are, but I got my hands on Delphi Cars diagnostics and run a scan:




So one fault under instruments and one under Multifunction. I couldn't clear either of them nor do I get much when I Google them. Wonder if the instrument fault code is something to do with the DRL?

Any ideas?

 

[Robert]

Must be AutoCom then.
I am afraid it doesn't have required functionality to adjust BCM coding.
You would need to use VCDS or OBDELEVEN.

But when you get your scan please post it here

 

[Pete24]

Yes it is Autocom.

Why would I want to adjust BCM coding? Will that get the DRL working again?

 

[Robert]

Did you try to disconnect your battery for a minute or so?
It would be good idea to reset the BCM.

 

[Pete24]

Just a quick update to close out this thread..... the problem turned out to be a blown fuse! I thought it was slightly odd that both lights are not on the same circuit, but I presume it must be a safety feature.

Thanks everyone for your help

 

[danbob81]

Hi @Pete24, what fuse did you change? I have a T6 and got the same issue. I cannot locate the fuse box for the DRL.