Blind spot sensor location

[Lee75]

Hi all, need some advice my left blind spot indication doesn’t seem to work as well and my right side one!
As soon as a vehicle starts to pass me on my right the yellow indication lights up in my mirror, and stays on until the vehicle passes! Now the left side is different only comes on after I’ve passed a vehicle but only for a few seconds! No faults have come up! Just would like some information on where I can locate the sensors for the blind spot detection! Many thanks lee.

Sorry forgot to add
I have a 2016 Citroen c4 grand Picasso flair 2.0 BlueHDi 150

[GiveMeABreak]

The blind spot monitoring doesn't have separate sensors - the system uses the parking sensors, specifically the ones on the side of the wheel arch or corner that face sideways. The unit in the wing mirror is simply the illuminated warning activated from data received by the sensors when a vehicle is overtaking or passing you.

The first thing I would do is check that the sensors are clean and not covered in any mud or grease. Be very careful with these, as they are obviously very sensitive. Check them all and give them a gentle clean.

A warning lamp appears in the door mirror on the side in question:

- immediately, when being overtaken,
- after a delay of about one second, when overtaking a vehicle slowly.

[Vasko]

Hello @GiveMeABreak

I noticed many of your answers regarding Citroen problems and I really appreciate your help in this forum. I have literally registered here just to post a question regarding parking sensors / blind spot monitoring. Because I see this thread is kinda similar to my question.
I have DS4 2012 and it has front and back parking sensors as well as parking assistant, so basically 6 sensors front and 4 at back. I recently had a problem with a broken wire to one of the front sensors and I was able to fix it myself by removing the front bumper and finding the broken wire. But as the bumper was out, I noticed plugs on both left and right side of the bumper with 3 pins (in flat order), that are not plugged into anything. My car from factory doesn’t have blind spot monitor, but there are same models of same year that come with that option.
So my question would be, since you said that Citroen uses the same sensors on the far left and right for blind spot, is it possible to somehow install the blind spot monitoring system to my car? And if so, what additional hardware or cables I need to buy to have it installed.
I am mildly experienced in fixing and installing stuff like this, so I hope it won’t be too much of a problem to try and do it. Also, I really tried searching for more details or videos or diagrams on how this works, but it wasn’t much information online about it.
Once again, I appreciate your help and I hope to hear from you soon.

[GiveMeABreak]

Highly unlikely. It’s not just about wiring, you need the additional sensors, the correct loom the correct mirrors, the mirror harness and on top of all that the BSI and head unit will likely need programming which you can’t do with Diagbox.

I really don’t have the time to deal with these ‘retro’ jobs personally as there are too many unknowns.

[Vasko]

Perfectly understandable, I didn’t expect it would be an easy job. But I am curious why did you say I’ll need additional sensors? From what I understood in your other reply it’s that the Citroen uses the same side sensors on the wheel arch, which I believe mine uses only for Park Assist at this point (to measure the distance between two vehicles). So I believe there is just some additional wiring that is needed, and obviously the correct side mirrors as well as some ECU programming, which I would definitely need help with from someone with a specialist equipment. Do you by any chance have any source for a diagram of a C4 or DS4 from 2012 that already has the Blind Spot Monitoring as default so I can see what parts are included?

[GiveMeABreak]

That's a Picasso, not a DS4 that I was talking about to give my answer context.

My C3 Aircross has Blind Spot Monitoring and Semi Auto Parking and has 12 sensors, so again different to yours and I forgot to mention also will have a different parking assistance ECU if Blind Spot is installed.

I can't advise on your DS4 as this may be different again and it will only bring up what your vehicle is fitted with not what it doesn't have.

[MelC4]

Hi Marc, how are you does my 2013 citroen c4 seduction e-hdi hatchback have automatic electric folding mirrors when you lock the doors.

[GiveMeABreak]

Hi, no it doesn't, just manual fold back.

[MelC4]

Okay thank you.