Technical Ducato 3.0 Multijet camper 2007

[Basilwatson]

Hi just a "quick " question.... ( I hope)

Customer has a Ducato 3.0 Multijet camper wit a burstner body. Im a motorcycle engineer so This isnt my cup of tea. so please excuse ignorance,

We were out and about ,,, turned the van off, did something came back , Van started ,,,we drove a few meters turned van off ,,, Wouldnt restart .. Immobilizer light? on turned van on and of a few times and it started up, Since then seems to be ok The Secondary battery maybe not holding a charge and has been of a solar panel trickle charge since the event, and the van has been starting ok
My question there for is, does this secondary battery have anything to do with the immobilizer circuit, My second thought is that my friend tends to have a few keys and a worn ignition switch may be an issue
My thoughts are remove and replace with a known bad battery or load test secondary battery ( main battery is a good one ) IF we can replicate the fault all good

any ideas that could help
I ave relevant workshop manuals ,,,but I dont know what to look for

Kind regards
Hope this makes sense

Stephen

 

[the green vanper]

Hello,

I'd start by disconnecting the habitation battery.

Few keys? Perhaps not all of them are programmed to the van (BCM)? which could cause this strange behaviour. There are two separate parts in the x250 Ducato keyfob: the PCB which operates the central locking and the transponder which operates the immobilizer. They are ment to be programmed separately to the BCM. They are completely independent in the keyfob, so even if the buttons open the central locking, it does not mean the van will be able to start.

I'd also connect MES to check for the errors and if all the keys are working properly.

 

[Basilwatson]

New battery on order
from the manual"
If the battery voltage remains below 8.5 V ± 5% for more than 30 minutes, the Body Computer Node NBC switches the control unit off in
order not to run the battery down.
The anti-lift control unit recieves the function deactivation request directly through the but" ( i before e except after c ,,,but I wont old that against them ahahah) My gut feeling is the battery ,,,

 

[the green vanper]

If the battery voltage remains below 8.5 V ± 5% for more than 30 minutes,

But this is for the starter battery.

 

[Basilwatson]

But this is for the starter battery.

Are the immobilizer and engine on different batteries? I couldnt make this clear ,,"chat gtp said the immobilizer was on the main engine battery ,,, However my symptoms suggest the Secondary battery to be the culprit and I couldnt determine this in the manual, Either way is a new battery I think ,,,

 

[NeilDD]

Vehicle and Habitation batteries should be independent systems, and only connected when the engine is running, to allow for the habitation battery to charge from the alternator as you go along.
Any vehicle immobiliser would normally be connected to the vehicle battery.
It might be worth seeing if you can get hold of the habitation wiring diagram, so you can isolate the habitation side completely from the vehicle (there should be a relay or similar which is only activated by the D+ signal from the alternator)

 

[Basilwatson]

Vehicle and Habitation batteries should be independent systems, and only connected when the engine is running, to allow for the habitation battery to charge from the alternator as you go along.
Any vehicle immobiliser would normally be connected to the vehicle battery.
It might be worth seeing if you can get hold of the habitation wiring diagram, so you can isolate the habitation side completely from the vehicle (there should be a relay or similar which is only activated by the D+ signal from the alternator)

yes Im with you on that relay..if Ive read things correctly, they suffer from corrosion due to location, chatgtp ( i know its quick and is a starting point ,,,I dont trust it ,,though)
In a Fiat Ducato 3.0 Multijet camper van (especially X250 or X290 models, 2006+), the electrical relays are located in several key places, depending on the function. Here’s a breakdown:

---

Main Relay and Fuse Locations on a Ducato Camper Van​

1. Engine Bay Fuse/Relay Box​

• Location: Left side of the engine bay (under the bonnet), near the battery or close to the left headlight.
• Contents:
  • Main system relays
  • Glow plug relay
  • Engine management relays (like fuel pump, ECU power, etc.)
  • Large fuses for fan, alternator, starter, etc.

2. Dashboard Fuse/Relay Box (Cabin)​

• Location: Behind the glovebox or access panel on the left side of the dashboard (near the driver’s door on LHD vehicles, or passenger’s side in RHD).
• Contents:
  • Interior lighting
  • Ignition relays
  • Power sockets, wipers, indicators, etc.
  • Central locking and immobilizer-related relays

3. Under Passenger Seat (in Camper Conversions)​

• Camper-specific equipment relays may be located here, including:
  • Habitation relays
  • Split-charge relay (for charging leisure battery from alternator)
  • 12V control relays for fridge, water pump, etc.
  • Battery disconnect relays

4. Behind the BCM (Body Control Module)​

• Location: Behind the fusebox in the dashboard
• Contents: Relays controlling:
  • Immobilizer
  • Lighting logic
  • CAN bus-powered accessories

---

Tips When Checking Relays​

• Look for a relay layout diagram on the inside of the fusebox cover.
• Use a multimeter or swap with a known-good relay to test.
• Check for corrosion or moisture, especially in engine bay boxes.

---

If your Ducato has been converted by a specific camper manufacturer (e.g., Adria, Hymer, Swift), there may be additional relay panels installed by the converter—often under beds, behind panels, or in utility lockers.


Would you like help identifying a specific relay function (e.g., fridge, starter, central locking)?

 

[the green vanper]

Please do not post chatgpt inventions, someone later might take it seriously.

Check the download section of the forum - you'll find a converters' guide - an official doc prepared by FIAT for the companies that are converting the triplets from the factory for different purposes.

I also assume that in the Buerstner manual there should be an information how to disconnect both batteries, or at least the habitation battery from the van.

There's also a FIAT owners' handbook available - it also should contain basic information on the immobiliser and the starter battery.

Then, it's a CAN equipped vehicle. Connecting it to MES or AlfaOBD with appropriate interface should also make things easier. Cheap ODB scanners from aliexpress or amazon won't do the job.

 

[Basilwatson]

Please do not post chatgpt inventions, someone later might take it seriously.

Check the download section of the forum - you'll find a converters' guide - an official doc prepared by FIAT for the companies that are converting the triplets from the factory for different purposes.

I also assume that in the Buerstner manual there should be an information how to disconnect both batteries, or at least the habitation battery from the van.

There's also a FIAT owners' handbook available - it also should contain basic information on the immobiliser and the starter battery.

Then, it's a CAN equipped vehicle. Connecting it to MES or AlfaOBD with appropriate interface should also make things easier. Cheap ODB scanners from aliexpress or amazon won't do the job.

VERY good point , I didnt think about that, Even though I wrote from chat gtp and I dont trust it ,,,there WILL be someone who ,,,,,,,, I use chatgtp as a starting point ,, then off I go and verify for myself,,,, but thats just me ,! Thanks for all the help ,,Will keep you informed of progress !