Ducato (X290) AdBlue issue

[Spuffington]

Hi guys - hoping for some collective wisdom here.

I'm on the verge of buying a motorhome based upon a 2020 Fiat Ducato Maxi (5t) 180bhp Euro6 auto chassis. All was ok and scheduled for collection today, when I got a phonecall saying the AdBlue light was lit and not extinguishing as expected. AdBlue tank is full. Mechanic fitted a new AdBlue sensor but issue remains. A phonecall to previous owners confirms this has been an issue since brand new. It has had 2x new AdBlue tanks from Fiat but problem persists. It counts down, yellow AdBlue light remains on even when full of fluid.

Anyone with any experience of this? I see there are the odd horror story of ongoing issues on some forums.

I spoke with a Fiat specialist this afternoon and he suggested that if the new tanks hadn't solved the problem, he'd be purging the AdBlue lines and potentially replacing the AdBlue injector. Plus then coding the system to calibrate the new parts. He seemed fairly certain that the issue could be resolved.

I am really very keen on this van but don't want to be storing up problems for myself in future. I'm happy to pay out to get it fixed once and for all (full system if necessary) and proposed a discount to this effect. The motorhome side is quite a rare layout at this age.

What to do?!

[5 In a Row]

I had the same issue in 2020 on a 1 month old Citroen Relay (?) which I assume is the same van underneath.
Van was rented and driven from Scotland to Czech and back - 2,500 miles and the adblue light never went away despite topping the tank up.

It may be a case of "they all do that Sir"

[Spuffington]

Thanks for your experience. Could very well be the same engine.

Have read somewhere that if you have a particularly heavy van with a large frontal/unaerodynamic footprint then it can increase AdBlue consumption beyond the ECU parameters and that can trick the van into thinking it's consuming so much it'll run out quickly and therefore light is perpetually on. However, I can only find this from one (Australian) source and struggling to justify it against all the talk of failed sensors, tanks, non-venting caps/imploding tanks, blocked injectors and gummed up lines.

[littlebasher]

Motorhome forums are full of stories about the Adblue systems on these vans

Current thinking is to keep the adblue tank full (to limit crystallisation) or to put some anti crystalline additive into the tank

My Boxer based MH hasn't given me any issues with it yet. When it does the whole lot will get mapped out.

[Spuffington]

Thanks. I'm doing a big read-up across the forums now.

I would naturally tend towards getting something mapped out (is it not illegal / MOT failure) but see it's not an isolated issue.

There seems to be conflicting information between keeping the tank brimmed and keeping it 1-2litres from the top as the sensor struggles to read unless there is an air gap at the top of the tank.

I'm tending towards biting the bullet and doing it - the van is perfect in all other ways (layout, mileage, transmission, engine, spec, history etc). Just want to make sure I'm not shooting myself in the foot.

[123DWA]

Spuffington said:

Thanks. I'm doing a big read-up across the forums now.

I would naturally tend towards getting something mapped out (is it not illegal / MOT failure) but see it's not an isolated issue.

There seems to be conflicting information between keeping the tank brimmed and keeping it 1-2litres from the top as the sensor struggles to read unless there is an air gap at the top of the tank.

I'm tending towards biting the bullet and doing it - the van is perfect in all other ways (layout, mileage, transmission, engine, spec, history etc). Just want to make sure I'm not shooting myself in the foot.

As somebody who runs a workshop, I would get it mapped out. You could spend thousands chasing it and still be no further forward. We have a Ducato car transporter which always had the light on, had it mapped out 2yrs ago & it hasn't been back on since.