C4 GP blind spot monitoring & indicator repeater fail

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

smokingblue
Posts: 6
Joined: 12 Dec 2017, 21:32

C4 GP blind spot monitoring & indicator repeater fail

Post by smokingblue »

Hi, newbie here, so hope posting in correct place.
Noticed our 65 plate (December 2015 build) blind spot monitoring had stopped working and wouldn't let you switch it back on, as it was due to go in for service (Independent Citroen Specialist) thought would leave it for them to have a look at and then I noticed that the o/s indicator repeater was also not working. Duly went in for service and garage checked fault, their conclusion was first thing would be to change repeater as this was obvious fault and Can Bus wiring can confuse fault finding and quoted £172.87 (£55.56 for repeater and 1 1/2 hrs labour!). So I thought being a practical chap I'd have a look round, found new non-OEM replacement on eBay for £25.79 and had a mooch around YouTube for fitting guide. found nothing for C4, but did find guide for Peugeot 208 with same style mirrors, so went ahead and ordered replacement. Getting cover off was not quite same as Peugeot video, although they looked same C4 had slightly different clips, but 15 mins later old repeater out and replacement plugged in, thought best to test before reassembly, so ignition on and nothing, still no o/s repeater, so plugged mirror wiring back in as it has connection for blind spot indicator light and tried again, still no luck.
So I'm hoping that some of you brilliant members might be able to shed some light on problem, or should I accept defeat and find a decent auto electrician?
User avatar
white exec
Moderating Team
Posts: 7384
Joined: 21 Dec 2015, 13:46
x 1445

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by white exec »

Hi, and welcome to the forum.
You might find one more Citroen aficionado in Midhurst here...
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26052
Joined: 15 Sep 2015, 19:38
x 2988

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by GiveMeABreak »

I classic case of replacing parts without finding the fault I think, and those prices are not far off a dealer's. The one difference is that they would probably have determined what the cause of the fault is.

If there is a fault with the blind spot monitoring, the Activation / deactivation button should flash for about 5 seconds before extinguishing.

The blind system has nothing in common with the repeater circuit. If you pop up your VIN I'll be able to have a look at the wiring for you, but likely suspect is a trapped wire in the door bundle. The wiring on these is very brittle.
smokingblue
Posts: 6
Joined: 12 Dec 2017, 21:32

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by smokingblue »

Hi Marc,
In the past I've found dealers follow the diags and that often means substitution and maybe dealers in West Wales are cheaper than in West Sussex, however if as you say the two circuits have nothing in common, apart from the wiring being in the mirror housing and pass through the door bundle, it is maybe coincidence that they both failed at the same time. I would have thought brittle wiring would not be so likely on a 49 month old car, however all advice gratefully accepted.
VIN is: VF7**************[VIN obfuscated, can be read by forum staff] and yes the blind spot activation button does flash before shutting off.

Cheers
Bernard
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26052
Joined: 15 Sep 2015, 19:38
x 2988

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by GiveMeABreak »

The Blind spot monitoring is linked to the parking assistance ECU Bernard. I've also checked the earths for the side repeaters and the blind spot monitoring and these are also separate earthing points - but of course all the door wiring for the door control module, windows, mirrors and other kit all have to go back through that door harness and back to the BSI at some point. I have seen some pictures in the past of the cut wiring at the door hinge point where this goes back into the engine bay, and also of the main wiring bundle in the engine bay, once the battery and engine fuse box is removed - the stack is obviously too tight and the strain just causes some of the individual wires to tear through.

The only way you can know for sure is to probably get an auto electrician with good knowledge of full CAN architecture systems to trouble shoot and trace the issue. There are a lot on interconnected harnesses here that makes troubleshooting a nightmare without the right tools. Your Picasso has the full electronic architecture, so is more complex. I only suggested that checking the door harness to engine bay wiring bundle as that would be the common factor / area for 2 separate systems to go down in the same location. The problem could of course be further down the line in the harness as I mentioned earlier.
C4 Door.PNG
smokingblue
Posts: 6
Joined: 12 Dec 2017, 21:32

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by smokingblue »

Thanks Marc, I guess that logic dictates I check if the park assist is working or not and also the loom at the door for any obvious splits/breaks. At least then I'll have more info to give to an auto electrician.
User avatar
GiveMeABreak
Forum Admin Team
Posts: 26052
Joined: 15 Sep 2015, 19:38
x 2988

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by GiveMeABreak »

The only things in the doors related to the blind spot monitoring is the actual notification symbol that is a simple on or off connection. All the other gear is in the forward and rear mounted ultrasonic sensors on the bodywork. So as the particular 2 wires to the alert symbol aren't multiplexed connections, it is unlikely to be too complex. but of course a break will do it! :-D
smokingblue
Posts: 6
Joined: 12 Dec 2017, 21:32

Re: C4 GP blind spot monitoring & indicator repeater fail

Post by smokingblue »

The thing I found strange was that it's both sides with the blind spot monitoring, but then I guess a fault with either side would take the whole system out.