Technical How to disable the reverse sensors

[PeterDucato]

Hi Forum,
My Ducato 2018 automatic has a Linnepe motorcycle carrier in the back that has it's own lights, like a regular trailer, and they are connected to the outlet at the back of the van with the euro plug. The owners manual of my van states that connecting the plug will disable the reverse sensors, but I still have this error showing up on my display in front. Seems like an error in the manual, or I am missing something here.
Is there a way to fix this, preferrably without cutting any wires?
Thanks!

 

[the green vanper]

Hello,

Attached the eLearn description on the parking sensors system.

There's a fuse that in theory could be taken out, but it could possibly trigger an error.

Perhaps there's a way to desactivate it in MultiEcuScan.

But it would be interesting to see why it's not working as described. So I've attached also the eLearn doc for that.

 

[rayc]

The nitty gritty from the attachments seems to be "Pin 6 of connector A of standard connector D073 sends the (earth) signal to inhibit the parking assistance device in order to prevent signals if the trailer is present."
Connector A is part of the normal trailer socket. In my old days of caravanning the car fog light was similarly disabled when the caravan was connected. Perhaps the parking sensors arrangement is similar in having a spring loaded 'switch' in the socket which would connect pin 6 to one of the ground pins?

 

[PeterDucato]

Thanks guys, really appreciate the help. Will look in to it and report back.

 

[RS3100]

Enable presence of a tow hook in the Parking Control Module with MES. But it probably depends whether the trailer socket has the inhibit connection and whether it is wired in accordance with the factory spec. A lot of aftermarket towbar fitters use aftermarket wiring kits for instance, which don't always work identically to the factory specification.

 

[PeterDucato]

The first thing I tried was taking out the F49 fuse, but takes out the complete trailer control unit, which I read afterwards in one of the PDFs.
Figuring out D073 on the wiring schema, I checked on wikipedia where that pinout translates to on a 13 PIN ISO 11446 connector, and found out that this connects to pin 12, which was an unused pin until 2012.
As I understand it - and RS3100 i think confirms it - is that my male connector should have an extra wire connected to pin 12 that I screw to the aluminum frame of the trailer. Which it very probably has not. Correct?

 

[RS3100]

The first thing I tried was taking out the F49 fuse, but takes out the complete trailer control unit, which I read afterwards in one of the PDFs.
Figuring out D073 on the wiring schema, I checked on wikipedia where that pinout translates to on a 13 PIN ISO 11446 connector, and found out that this connects to pin 12, which was an unused pin until 2012.
As I understand it - and RS3100 i think confirms it - is that my male connector should have an extra wire connected to pin 12 that I screw to the aluminum frame of the trailer. Which it very probably has not. Correct?

I haven't towed for many years since I switched to a motorhome, so I'm not exactly conversant with the pin numbering on towing electrical connectors and longer. But even with the old 7-pin sockets I remember that a new version was introduced with an eighth terminal to signal that the trailer plug had been connected, and disable the rear fog lights on the towing vehicle.

So I think it is this signal that is also now used by the towing vehicle to recognise the presence of a trailer or load (m/cycle carrier) on the rear of the vehicle, when the lighting plug is connected to the towbar wiring socket. But it does also depend on that additional "switch" terminal on the vehicle wiring socket being connected correctly to the vehicle wiring to enable the function to work, and different vehicle manufacturers use different proprietary kits to interface with their vehicles. Aftermarket kits sometimes take alternative routes to connecting the wiring and sometimes avoid the signal function altogether.

The first vehicle I had where I remember things starting to become more complex was a Vauxhall Carlton, and the Vauxhall wiring kit came with various relays that had to be fitted in different locations on the vehicle. One at least was simply a matter of plugging the relay into a vacant slot in the fusebox. Another had to be spliced into the main wiring loom behind the footwell kick panel. A lot different to just connecting a few wires into the rear lighting connectors on the vehicle.

But as long as the wiring is as per what Fiat expect, as I understand that reprogramming the parking control module both activates the function to disable the rear parking sensors when reverse gear is selected and the presence of a trailer plug is detected, and alters the pattern of the two innermost sensors so that the tow hook will not cause false detections at all other times.

I don't tow a trailer with my van, but as an example when I ordered my van I specified factory fitted reversing sensors. The motorhome converter that I bought my van from also offer to fit aftermarket reversing sensors as a cheaper option than ordering the base vehicle with the factory sensors already fitted. But when they fit the aftermarket sensors, they simply wire in a rocker switch fitted on the dashboard, which disables the reversing sensors completely when the driver operates the switch. So it is no longer an automatic system and the driver has to remember to operate the switch depending on whether he is towing or otherwise, to change the behaviour of the reversing sensors.

 

[PeterDucato]

I have replaced the lights and cabling on the carrier recently, and even the original Linnepe wiring did not have any grounding. And already then, I got the parking sensor warning light.
So this function explained in the trailer setup PDF: "Pin 6 of connector A of standard connector D073 sends the (earth) signal to inhibit the parking assistance device in order to prevent signals if the trailer is present." strongly indicates that a connector that supports an automatic disable has to have that pin connected to ground.

I know that the parking sensors work when I put the van in reverse, I have ridden it some time without the carrier. There seems to be no reason to disable the automatic sensor for an attached connector, unless some company designs carriers or trailers that are transparent, and still provide wiring to disable automatically on their connector, which seems rather unlikely. So I don't think any ECU type config is needed. At least I hope so.

Fitting a rocker switch connected to the control unit M181 avoids all issues of course, and the trailer/carrier connector can be of the dumb variety.
But I don't feel like opening the dashboard. I don't see them next to the fuses.

Herminia is calming down a bit here in Spain, time to get cracking.
Thanks for all the help!

 

[the green vanper]

As far as I can see, the M181 should rather be located by the main fusebox in the engine bay, behind the left headlight.

But can be mistaken, it's a 2D image only.

 

[PeterDucato]

Well, I put that extra wire on pin 12 of the Euro 10 pin connector, and the good news is that i did not blow a fuse
The not so good news is that the dashboard still displays the "parking help unavailable" error.
So… or I did not figure out the wiring correctly, or the automatic detection is switched off in the ECU.

OK, no worries. next maintenance I'll ask if the ECU can be checked for this. In that turns out to be the reason, it was still OK to attach the extra wire, because it's needed as well for things to work.

Anywho, I'll post how thing turn out in this thread, probably in a few months.
Cheers! -- peter

 

[rayc]

Well, I put that extra wire on pin 12 of the Euro 10 pin connector, and the good news is that i did not blow a fuse
The not so good news is that the dashboard still displays the "parking help unavailable" error.
So… or I did not figure out the wiring correctly, or the automatic detection is switched off in the ECU.

OK, no worries. next maintenance I'll ask if the ECU can be checked for this. In that turns out to be the reason, it was still OK to attach the extra wire, because it's needed as well for things to work.

Anywho, I'll post how thing turn out in this thread, probably in a few months.
Cheers! -- peter

What happens if you ground Pin 6 of connector A?

 

[PeterDucato]

Hi Ray,
I found out that pin 6 of connector A maps to pin 12 of the ISO 13 (sorry not 10 as I wrote above) connector, the actual plug that is used.
The Fiat PDF does not document up to to the connector level, probably because of different standards in different regions of the world.
Doesn't show here yet: https://en.wikipedia.org/wiki/ISO_standards_for_trailer_connectors
Shows up here, but doesn't say yet where pin 12 is used for: https://en.wikipedia.org/wiki/ISO_11446
And finally shows up here: https://en.wikipedia.org/wiki/Trailer_connectors_in_Europe and explains that pin 12 is used for trailer detection.