C4 VTS brake lights failure
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Thread: C4 VTS brake lights failure

  1. #1
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    Default C4 VTS brake lights failure

    Guys,

    Both rear brake lights on our C4 VTS have failed simultaneously, although the upper brake light in the tailgate works fine.

    There are no fuses listed for the brake lights.

    I have checked the bulbs, and they are all OK, and replaced the brake switch, but the problem remains.

    Obviously, it's a continuity problem with the wiring feeding power to both the rear brake lights, with presumably the one source feeding both lights. The two rear brake lights are in the body, so presumably it is not the common problem of wiring chafing and breaking where it goes through a rubber sheath into the tailgate, and in any case the tailgate brake light is working OK.

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    Checked all the usual Internet sources, and the same problem has been experienced by others, but there is no clear solution posted.

    Anyone here experienced, and solved, the same problem?

    Any information would be appreciated, as we cannot legally drive the car at present.

    RobL

  2. #2
    1000+ Posts Ken W's Avatar
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    I presume all other lights in the back clusters are working OK? If not you could have lost earthing. Check for voltage at the bulb with respect to chassis from both of the bulb terminals. Check if cleaning any connectors helps the voltage through to the bulbs.

    Are these bulbs controlled by an electronic module that receives signals on the Can bus? These questions start to need a circuit diagram that you can get for a citroen service account that has some $ in the subscription or the Haynes C4 manual might have them.

    Check out some suggestions and report back. Any auto electrician who knows peugeots or citroens should be able to help.

    Ken W
    Last edited by Ken W; 22nd July 2015 at 05:08 PM.

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    Thanks, Ken.

    All the other lights in the back clusters are working fine.

    I have checked all the relevant contacts, and connectors that I can get at.

    The two rear brake lights failed at exactly the same time, so there a common problem. I am getting hold of some circuit diagrams, and, if I can't solve the problem myself, the next step is to go to an auto electrician.

    I will keep you posted on progress.

    RobL

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    Here is the diagram for snail models - C4 VTS brake lights failure-stop.jpg

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    Thanks seasink,

    I have been able to get hold of a number of wiring diagrams for the C4 VTS Coupe. The tailgate light, and each of the rear brake lights, each have independent wires leading from the BSI (Body Control Unit), so the only common failure point for the two brake lights is at the BSI.

    I find on the Net general agreement that the Citroen/Peugeot BSIs are prone to failure. However, before replacing them, everyone recommends that you should first try a BSI reset, as that often cures the problem. The same BSI reset procedure is given on a number of websites, and an example from the Citroen Owners Club UK can be found at Citroen,BSi Reset,berlingo,xsara,piscasso,c5,c4,c3,c2,multispa ce

    I will try that first, see what happens, and post the results.

    RobL

  6. #6
    Now go make me a sandwich Hotrodelectric's Avatar
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    Edit: you already did what I suggested. Never mind.....
    The measure of your character isn't what you do when people are watching- it's what you do when they aren't watching.

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    Update:

    Reset the BSI, and checked some more fuses on the basis of the circuit diagrams.

    Still no joy, so it is booked in to a local highly recommended auto electrician, who has done work for me in the past, on Monday morning.

    I hope they can sort out the problem, as we are effectively without the C4 until it is fixed.

    Fortunately, we have a spare family car, an immaculate 1994 V6 Magna, which has been entirely reliable over the last 20 years, and almost 300,000km. Always handy to have a back up vehicle if your main cars are Citroens.
    FIVEDOOR likes this.

  8. #8
    1000+ Posts Ken W's Avatar
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    Rob,

    When you did the BSI reset, did you have to set the time and date? If not then I would say that the BSI didn't reset. Try the same again but leave the battery disconnected for a few hours.

    As an alternative, I would suggest disconnecting the lines from the BSI to the rear brake lights and triggering a solid state relay from the centre brake light that will supply main 12volt power to the two brake lights.

    It would be interesting to get Diagbox interrogaqtion report of the car and see what it says wrong as it seems to be able to report exactly which bulbs are blown and other electrical gremlins.

    Cheers,

    Ken W

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    Thanks, Ken.

    Yes, I did have to reset the time and date, so on that evidence the BSI did reset.

    I know the guys at the auto electricians, so I will see what they come up with.

    The suggestion regarding the relay is a good one, and could be a possible solution if they don't find the actual problem.

    The way the loom is packed in, and the density of the multiplex wiring could make that suggestion a bit tricky to implement.

    Next update: Monday.

    Thanks to all for your suggestions and assistance.

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    Monday and (hopefully) final update.

    The good news is that after the visit to the auto electrician this morning, the brake lights are working again.

    They thoroughly checked everything, replaced both brake light bulbs, both of which I had previously checked, with new bulbs, and voila, everything came back on line. They did not find any faults.

    The bad news is that exactly why it is all OK now is not clear, so I will monitor the situation, but after driving it fairly extensively this afternoon, all is fine.

    It may be a interaction of everything I had already done (new brake switch, etc.) and the brand new light bulbs.

    Hopefully, this is the end of the story, and I will put it down to experience.

    Thanks again to all.

    Cheers,

    RobL

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