K9 Towbar Electrics

[IMH89]

Hi everyone.

I have just fitted a Tow Trust towbar to my Berlingo and I bought a dedicated Citroen electric kit to go with it. Fitting was more or less ok, but nothing works and I'm now told that I need to visit a Citroen dealer so they can 'turn on' the towing function on the ECU. In buying the dedicated electrics I thought it would be plug n play so I'm a bit miffed that I still have to seek dealer help. Would I have been better off buying a universal electrics kit? Anyone else experienced this? What can I do besides visit a dealer?

[Sol]

Nope, with the Multiplexed BSI system, you cannot splice anything into the existing wiring to the rear lights, brake, tail, reverse, indicator or fogs. You risk permanent damage to the BSI outputs and that is an eye-watering repair cost. This rules out adding generic kits as they need spliced in.

Big warning here, honestly do not try this.

(Technically it is possible with a solid state relay for each and every lighting function and an add-in fusebox to be controlled by the multiple relays, so no damage can occur to the multiplexer - but - this is way more work and complex than plugging in the factory module, and getting it coded to the vehicle.)

Also as you found, if you add a module that the car (or van) was not supplied with, then it needs coded (programmed) into the system so the BSI knows it should be there. Can be done using Citroen Diagbox but on your vehicle being as new as it is, you will indeed have to get Citroen to do it, as the hacked versions of Diagbox on eBay cannot do vehicle configuration after 2018 models as it all moved online to PSA.

All modules are CANBUS or VANBUS, so really high-speed or medium-speed data bus connected. So, when you press a button the computer (BSI) has to find the device responsible for that function and send a message over the right databus to tell it to actuate that function - this requires the modules to have a CANBUS or VANBUS address and be on the list of modules in the BSI memory.

This is why coding is required.

[IMH89]

Thanks Zion. I will get it booked in. Is it a big job for the dealer?

[Sol]

Hi there, no it should be straightforward. Some dealers are dumber than others (!)...but most should get (understand) what you want to do. It only involves about an hour of labour, hooking it up to their online Diagbox system and then performing a configuration change to add the rear towing ECU to the configuration in the BSI.

Explain to them you had the official Towing ECU added and it now needs to be coded to the vehicle configuration. I expect a busy main dealer would have done this a few times. Alternatively if there is a PSA independent in your area, or near it, then they could do the same job and probably for less money, though I would hope it isn't too dear to get a single config change carried out.

[Concizat]

I recently fitted a towbar to my 2017 B9 Berlingo Multispace and used a Maypole TEB7AS bypass relay for the electrics. They are designed specifically for Canbuss systems, using a separate 12 volt supply.
It was easy to install and works perfectly. I've done 12 hour trips to France towing a trailer with no problems.

[IMH89]

Hi there, no it should be straightforward. Some dealers are dumber than others (!)...but most should get (understand) what you want to do. It only involves about an hour of labour, hooking it up to their online Diagbox system and then performing a configuration change to add the rear towing ECU to the configuration in the BSI.

Explain to them you had the official Towing ECU added and it now needs to be coded to the vehicle configuration. I expect a busy main dealer would have done this a few times. Alternatively if there is a PSA independent in your area, or near it, then they could do the same job and probably for less money, though I would hope it isn't too dear to get a single config change carried out.

My local dealer has quoted £129 (inc VAT) and they need the van for 90 minutes to carry out this update.
Why do new vehicles need such a sensitive electric system? Seems unnecessarily complicated.

[Sol]

It's been like this since 2006 or even earlier. A Vauxhall Vectra I had of 2003 vintage had 7 different ECUs and remappable lighting so that if a bulb failed, another one took on its job.

Multiplexing allows more functions with less wiring, which saves production costs. And having programmable options modules means less extra hardware needs added to allow upgrades or different option packs. Berlingos have had this system since the M59 onward through the B9 and now the K9.

[uk_friendly_fire]

I recently fitted a towbar to my 2017 B9 Berlingo Multispace and used a Maypole TEB7AS bypass relay for the electrics. They are designed specifically for Canbuss systems, using a separate 12 volt supply.
It was easy to install and works perfectly. I've done 12 hour trips to France towing a trailer with no problems.

But you missed out on trailer stability program. This carries out differential braking to reduce snaking. OK for a small goods trailer, but I tow a 1tonne caravan and wouldn't want to miss that out!

[Guanock]

I fitted a tow bar to my 2018 K9 last week and booked car into a trailer specialist for supply and fit of dedicated electrics plus coding.
That was carried out today. As soon as I returned home I coupled up to the caravan and can report everything is working perfectly: lights, fridge, battery charging, rear fog disabled, reversing bleep disabled, lane departure disabled.
So all is good and a very tidy job too.

Geoff