Flashing brake lights on Citroen Berlingo 2017 HDi

[Zion]

Hi all, brake lights are mysteriously flashing, no error codes except a weird U3FFF(FF) when scanned and a U1400(83) which I know about, that's the LIN network to the alternator, which is currently disconnected otherwise the alternator drops out of charge - if the LIN Charge Control wire is unplugged, the alternator charges as it should (still to be resolved)

Anyway, the U3FFF(FF) would appear to be a fault code relating to fuel pressure but the actual pressure is within what I would expect, and also why a U code when it should be a P code.

If I switch the sidelights off, the brake lights flashing continues, is rapid and irregular. No pedal coherence errors recorded, unlike when I purposefully brake while also on the throttle, which produces as expected, a coherence error. Without braking on purpose while pressing the throttle, this flashing of the brake lights does not trigger the same error. This makes me think it's the BSI output flashing the brake lights, not the switch inputs telling it to do so.

I just got hold of DiagBox v9.68 so will try scanning with that today if I get the chance, as the older version 7.83 does not recognise the EDC17C60 engine ECU, hence I could not scan it properly. Up to now I had to use non proprietary diagnostics which as we all know, is not good on PSA cars. If I run a "code clear" from the generic software then for a time, the flashing will stop. Very odd. The next day, it would be right back.

Anyone have any light they can shed on this?

I have still to strip the plastic cover off the (remote) brake switches on the passenger side but due to the lack of "coherence" error, I feel the switches are not the issue, will see what DIagBox live actuator testing throws up on the status of those.

[GiveMeABreak]

Not sure about your code U3FFF(FF) as that's not being returned as a recognised fault, but your vehicle is still being flagged up for an after-sales campaign, Did you contact Citroen to find out what it is related to yet?

[Zion]

Thanks Marc, I noticed that recall flag too but haven't contacted them yet. Unfortunately in my part of the country, a single garage chain has the rights to all Citroen dealer franchise operations and I would not get them to repair a child's bike, though for a recall, I may have to. There are no genuine Citroen dealers for hundreds of miles from me, only this multi-brand franchise. It's a shame even when logged into ServiceBox, it does not tell you what the campaign recall involves. I guessed it was the Adblue cap, as mine is the entirely blue one, not the one with the white vented disc in the center. I could be wrong.

I also could not find that fault code in my own documentation (Citroen stuff I have collected over the years) but assumed it could be too new a code and wasn't in my lists. The pitfalls of using non PSA software on them is evident. I will scan today at lunchtime, using v9.68 and should get a proper set of codes returned.

[GiveMeABreak]

I would certainly give them a call at least, as these are not always minor things and some members have found they have had the timing belts and injection systems replaced, so I would at least find out from a phone call.

Obviously I can't speak for your franchised network, but to become one they have to have the same training and qualifications to work on PSA vehicles as any other dealership - but like anything there are technicians and there are better technicians...

[Zion]

Haha tried 5 times, hung on till I had to give up, waiting on the Service Dept. answering the phone.

So far, I scanned with 9.68 DiagBox, had a weird fault on the BSI - "F5FF Unexpected re-initialisation fault coming from the BSI" - cleared all, that one did not come back. On the flickering brake lights, I tested the switches, all good. Brake pedal not pressed unless I actually press it, yet the brake lights flicker merrily away without it realising.

One thing I do see, the global scan says I have BTC and BSR (trailer and body modules) which when queried, show "?????" for serial number & manufacturer and 0 for all other items. Testing them in actuator testing mode, test starts but says "an unknown error occurred while testing" - my thinking is that someone has told the BSI these items exist but they do not. So, into BSI repair > configuration > manual configuration - yet hey ho, they are marked "ABSENT" so I have no idea why Global Scan finds them as active modules (green icons and everything) and why the brake lights flicker, I am sure is somehow involved.

[GiveMeABreak]

Are you sure nobody has fitted LED bulbs to ANY of the exterior lamps? This is a symptom associated with LED bulbs not designed for halogen fitment and the standard lighting circuits.

It's also known that LED replacements can cause BSI faults like this.

[Zion]

Now it did have an LED brake light on the 3rd one (high level) as it came as a unit with a rear camera.

I have now unplugged that, but it is still doing it despite no LEDs being connected now. I do intend to fit a standard 3rd brake light with the ordinary bulb and see if it behaves, I had thought the LED was initially to blame, knowing it doesn't like them and was given the old one in the deal with the van. I had thought it would stop the flashing once the LED was removed, but it is still doing it.

Oddly, clearing codes resumes normal operation till the next time it is started, yet no new codes appear. It does of course now have the fault code for "3rd brake light missing".

Does this kind of fault resolve itself, if the LED is removed and the standard bulb reinstated?

[Hell Razor5543]

It is possible that the 3rd brake light was LED from the factory. Marc will be able to clarify this. My C5 (which is a 2007 reg) has normal bulbs in the tail-light clusters, but LEDs in the 3rd brake light.

[GiveMeABreak]

The factory third brake light is not LED, so I'd remove it and refit standard bulbs. It may take a while to stabilise, so once you have refitted standard lights do a BSI reset (BSI Reset / Battery Disconnect / Reconnect Procedure) and see how it goes. But I would double check the other lights in the rear clusters for any LEDs as these can and will interfere.

[Zion]

Thanks for the support - it has been put back to standard, no other LEDs left and as expected it took a bit of a daft turn, 3rd brake light works, then it doesn't, then it does, then etc. etc. but no phantom brake flashing at last. It definitely throws a strop for LEDs which aren't meant to be there. I'll do a reset next.

[wheeler]

This is a bit of a strange one right enough.
Does it have any towing electrics fitted? Or any other non standard electrical equipment beacons, light bars etc?
Do the brake lights flash when stationary ?

[Zion]

They flash whether stationary or moving. It has no trailer or socket hardware fitted, yet the global scan identifies BSR & BTC (Trailer Relay) modules, though the BSI config states they aren't present. Weird? No beacons, lights, anything like that, it's as it came new as far as I know, bog standard van. Now I have removed the only LED it had which was a Dolphin Systems rear brake light with camera, and refitted the standard bulb but left it hanging inside, so I can watch it. When it lights up under braking, usually it works and no flashing. Then it starts randomly flickering, and stops working on the footbrake the next time you start the engine. This continues for a whole journey, till switched off. The next time you start it, the 3rd brake light works (I see it light up inside) and will work all journey, then returns to the flashing and stops lighting at all again in a cycle.

I will try a standard BSI reset, which I don't think will do anything but worth a try. It's usually where I point users myself when they have issues.

Oddly too, the status of the brake switches is always "off" unless I press the brake, using the live data / actuator functions in DiagBox. Since the BSI operates the brake lights, based on pedal switch input, the flickering must be the BSI itself tickling the output lines to the brake lamps. Very weird. It isn't rogue switches triggering the inputs to the BSI for brake lights, it is only the outputs flickering live. It seems not to realise it is doing this.

[Zion]

Latest on this issue, I have pulled the brake switch, all looked ok but I extended the adjustable plunger to make the switch operate a wee bit later, and that seems to have cured it - odd that the BSI did not report the brake switch being operated while the throttle was in use (coherence error) but it could be only one contact was triggering and not both as is the case when you actually press the pedal.