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Reverse bulbs/BCM - Urgent advice/opinion needed!

Posted: Mon Feb 21, 2022 5:55 pm
by joshuabourke
Hey guys,

I was hoping for some pretty urgent advice or opinions on the situation I'm currently facing with my 2010 Scirocco 1.4L, as the MOT retest deadline is Wednesday and I'm not totally satisfied of what the mechanic is saying the problem/solution is. For reference, I've already sank over £600 into the car to fix problems arising from the MOT and I'll be looking at another £800 potentially with what has been said by the mechanic.

In summary, either of the reverse lights are working however each of them is showing a different problem. The passenger bulb is constantly turned on when a bulb in placed in it whereas the driver side never turns on, despite using the same bulb when testing both sides. Initially the mechanic thought it may have been the reverse switch however when this did not solve things, they changed their opinion to thinking that the body control module/BCM is the issue. However I am not convinced by this, and frankly desperately do not want it to the case given the cost of replacing it.

The main reason I doubt the BCM is faulty is the fact that the driver side reverse bulb was working approximately 3 weeks ago, with the passenger side not having worked in over 6 months to my knowledge. The passenger side did not have a bulb in it at that time, due to the fact it remains on, so I opened the driver side to retrieve the bulb, that was working perfectly fine, from there. When realising the issue with the passenger side, I put the driver side back together however noticed in the following days that the driver reverse light was no longer now either. Correct me if I'm wrong but this would suggest that the problem lies elsewhere from the BCM as it had worked within the last month, and the passenger side is still drawing power, with the light never turning off when a bulb is inserted.

Also to mention in case it affects things, I have had the battery replaced recently on the car and it has aftermarket LED daytime running lights at the front. I also had rear parking sensors fitted in the last month however I do not think this is an issue as the driver side reverse light had worked after the sensors had been fitted.

Any suggestions/opinions would be hugely appreciated, and unfortunately time is of the essence with the mechanic having dragged his feet getting the car in. Of course also, the priority is to get the MOT passed so even if there is a suggestion as to a short-term/temporary fix. Essentially I am desperate for this to not be a BCM issue but understand I am not too knowledgeable on things and would be open to being corrected or steered in the right direction!

Re: Reverse bulbs/BCM - Urgent advice/opinion needed!

Posted: Wed Mar 09, 2022 4:31 pm
by chelspeed
Are they identical wiring plugs both sides? If so take both light units off the car and swap left to right. If the faults stay on the same side then its a wiring / control issue. If the fault swaps sides then it's a light unit issue.

Have you done a VCDS scan? I think that would tell you if it was a control module issue.

Have you checked the wiring diagram? I'd be surprised if a control module had separate reverse light wires to each side which it would need to allow different faults on different sides. I would expect one reverse light output from a control module and one wire to one side then on to the other side. If so then wth two different faults it can't be a control module or wiring issue.

Do you even need a reversing light for the MOT? If not then it will be if fitted it must work sort of thing. Take both bulbs out, put black insulting tape over the clear lens (while it's in for the MOT) and jobs a good one.