Overactive parking sensors

[jml]

Recently the near side front parking sensor warning on my C8 has been indicating a close object, when none is there. As soon as I select first or reverse the display indicates something very close at the near side and inner near side and the sound blares out.

I checked the sensors for any dirt and then replaced them, but it has made no difference. Are all sensors the same ?

I’ve checked it on my recently acquired Diagbox and that shows absolutely no faults.

Any suggestions folks ?

[GiveMeABreak]

Hi Julian

The problem is that barring a permanent Parking ECU fault itself, or a permanent lack of communication with a parking sensor, Diagbox won't be able to detect a fault - but may have a temporary fault recorded in the logs that you can check.

Because the sensors are only active in forward and reverse gears, the sensor feedback is only working at this time.

So my question would be have you used a car wash, pressure washer on the car recently? This can result in water getting onto the wiring harnesses and running down into the sensor plug wiring and getting inside. Once this happens you will may experience intermittent faults with sensors until they are fully dried out (as long as there is no internal water damage).

So I suggest you try connecting Diagbox up and undertaking some live tests as you activate reverse and forward gears and see if it reports any faults when the system is actually active. If not, then you may have those specific sensors noted starting to fail.

As for the sensors themselves both front and rear are the same - HOWEVER, be aware that there are 2 types of sensors for the C8, depending on the electronic architecture of the vehicle, so you need to bear this in mind if you have recently or are thinking of replacing sensors on the aftermarket as they have different part numbers.

In your case you need the CAN CAN versions:

Either 659095 (unpainted) or
6590Q2 (primed)

[jml]

Thanks Marc,

I did pressure wash the car fairly recently, so I guess that could be the problem - I’ll check that out. However, although I did originally change just the one sensor, that didn’t seem to make a difference so, as I had a complete front loom (from a CAN C8) with four sensors (that I believed to be ok) I then changed the whole loom but still had the problem.

As I’ve now got 8 sensors (4 from my original loom & 4 from the replacement that I’ve got) I wonder whether it’s worth swapping sensors around to see if that pins the problem down any more closely ?

On Diagbox it came up with something like ‘activate the sensors’ and I tried standing in front of them with the ignition on and in first gear but it didn’t show anything.

Would you know where the parking ecu is on a C8 ?

It’s all a bit ironic really as one of the (few !) things I always used to be able to do was park in tight spaces and when parking sensors first appeared I though ‘what a waste of time’ ! However after living with them for over a decade I’ve become totally reliant upon them as they (used to) work so well on my car !

Thanks for your advice - I’ll keep you updated. It’s just a pain that you have to pull the bumper off every time you want to access the sensors.

Cheers and thanks again.

Julian

[GiveMeABreak]

NO problem

Here is where the ECU is located. Item (5), located on the inside rear right wing, probably behind the trim or storage compartment / rear wing light cluster area.

Better picture here:

[jml]

Thanks Marc,

I've seen that ECU before, but didn't realise what it was !

I'll try swapping some sensors first and let you know how things go.

Cheers

Julian

[jml]

Hi Marc

Update on parking sensors.

Although I had a loom with what I thought were 4 good sensors for the front, replacing that didn’t cure the problem. When I saw some cheap sensors on EBay I thought ‘what have I got to loose ?’ so bought four and fitted them to the front and all was well Hooray.

However, after about a week of working perfectly I’ve now started getting the ‘parking assistance inoperative’ warning come up when I start the car. Plugged in Diagbox and, to my surprise, it came up with the notice that all REAR sensors are faulty ! Codes FBC6, FBC7,FBC8 & FBC9, plus ‘sensor supply fault’ - short circuit to negative.

Is there any way to check sensors to see if they are good ? Once I’ve checked which of all the ones I’ve got are good then I can check the feed from the ECU that you kindly identified before.

Cheers

Julian

[GiveMeABreak]

Hi Julian.

It's very unlikely that all 4 rear sensors have gone - so I suspect it is an intermittent supply fault that is causing the 4 fault codes each for the individual rear sensors to show up. As it is all 4, I would ignore the sensors to start with as it is highly likely to be the Parking Assistance ECU or the wiring to or from it.

All these faults indicate an absence of the negative - so I would suspect the Earth is the culprit.

ON your Parking Assistance ECU, there will be an 18 pin black connector and a 12 pin blue Connector. On the 18 pin connector, take a look at pin no. 1. Which is the common earth supply for the ECU and subsequently all the sensors.

There is only one earth for the ECU and this is Earth Point MC71.

Now looking at the location - it is hard to tell exactly where it is from this picture, but it does seem to sprout off the main right loom as you can see:

Click Image to Zoom

Crimp Point EM71B would seem to collate the earth supplies from various kit

This is the equipment that use Earth Point M71A for their earths: 2635 Right Hand Tail Lamps 7500 Parking Assistance ECU 6215 Rear RH Door Open Switch 3107 Luggage Compartment Right Hand Lighting CP00 Rear 12V Socket 6234 Doors Actuator Cut Off Control Unit

So somewhere EM71B will branch off to the actual Earth Point

So as the other Equipment that shares the same Earth Hard Point that is assumed to be working, maybe it is the specific earth wire inside that loom that has a problem?

[jml]

Thanks Marc,

That’s brilliant and of even more help than I could have dreamt of - thanks so much.

I’ll try to check that out in the next week or so and let you know how I get on. As it’s an earth I’m looking for I guess I could fit a temporary earth to see if that cures the problem. If it does then I could follow the original earth lead back to try and see where the problem is..

Cheers

Julian

[GiveMeABreak]

I've just updated my post above to give a bit more info and diagrams that may help Julian. It seems the Earth Hard Point is almost centre-right of the floor pan area, but can't be sure from the angle of the pictures.

[jml]

Thanks again Marc.
Yes, to confirm, I don’t have any problems with any of those other components so that will help me narrow down my search.
Somewhere I’ve got photos I took when I removed the entire rear carpet a few years ago and I’ll try to search those out.
I guess my idea of a temporary earth just to the parking ECU may be worth trying ?
Thanks again - I’d be lost without you
Cheers
Julian

[jml]

Just found my pictures and thought I’d post it on here just in case it’s ever of help to anyone else - although I don’t think there are too many C8 owners on here.

Just remembered, that my rear 12v outlet doesn’t work either - maybe I should double check all the other items you mentioned Marc !

Cheers

Julian

[attachment=0]

[GiveMeABreak]

That may be a clue then Julian, as the 12V Rear Socket (CP00) is also contained in that loom and uses the same earth point.

[jml]

True but, maybe unfortunately, the RH tail light and the RH door open switch all seem ok so it doesn’t look like a ‘central’ problem.

Wish me luck with my investigation

Cheers

Julian

[jml]

Well, I spent much of today pulling out the interior rear of my car and everything was just as you described it, thanks so much Marc. It’s amazing the lengths PSA have gone to to conceal fixings for aesthetic appeal, however it means you often have to remove another component to release the one you want to remove - and sometimes even remove yet another to release the second one !!

Unfortunately, after a few false hopes, I’m afraid to say I’ve failed to fix it. When I got the quarter panel off, I immediately saw the ecu and disconnected the 18 way connector you described. I then noticed that the other one appeared loose and I thought that could be a problem but then I realised that I’d probably dislodged it accidentally myself. Later I detected a little bit of damp and thought that maybe water ingress was causing the problem, as you’d suggested earlier. However I removed and opened up the ecu and it was bone dry with absolutely no sign whatsoever of any water ever having got into it. It transpired that the water was from the rear washer tube and couldn’t have got near the ecu anyway.

The apparent clue that the 12v outlet wasn’t working turned out to be another red herring as it transpired that I hadn’t reconnected it when I last had that panel off. Oops !!

I checked terminal one of the 18 way connector (How on earth do people get probes into those connectors ?? ) and it was a good earth. Nevertheless, I spliced into the lead and added another good earth to be on the safe side. I found the MC71 earth point and that looks good.

Checking it then on Diagbox it just showed ‘short circuit to negative’ although nothing to point to the rear sensors like before.

Maybe I should check all the other wires into the two connectors ? And, again, I’d just ask how anybody manages to get a probe or some such into there.

Because this all started with the front sensors (the rear ones have always worked perfectly) I pulled the front bumper off just to check the connections and that I hadn’t made any mistakes (like I had with the rear 12 outlet !)

Any other thoughts or advice would be very gratefully received !

Cheers

Julian

[GiveMeABreak]

Hi Julian

If the circuit has been tested with a new earth to pin 1, and the ignition is on and it is still not functioning, it is possible that the fault is internal to the ECU. This may be a cracked small dry solder joint for example, that would be hard to detect visually.