Is there a way to tell if AdBlue has been deleted?

[dispatch31]

Hi guys,
First time posting here.
A month ago I bought a second hand Citroen Dispatch 2.0 BlueHDI 2021, with 25,000miles on the clock, from VanBase with RAC inspection. There is no problem with the van, it runs well, BUT....

I have been playing with DiagBox 9.150 and I am intrigued by the feedback I get on the AdBlue system.
DiagBox says that the AdBlue ECU is not present (this is perhaps normal) and when I look at the denox system data (via engine ECU) I get some telemetry (adblue level) but the nox readings and the adblue pressure readings are all at zero.

Is it possible that the adblue system was deleted from the van by the previous owner? Is there a way to tell? The van is under 6 month RAC warranty so if the van is not stock/legal I would like to find out before the warranty expires (5 months left on it now).

Any help would be appreciated,
Thanks,
Arnaud

[GiveMeABreak]

There is no Adblue ECU for a start - the management of the Urea operation is handled via the Engine ECU.
Adblue pressure is very low in any case, but won't be operating unless the engine is running, so that may be why there is not pressure reading - and the same for NOx emissions - if it's doing it's job there shouldn't be any - but again won't register in any case unless the engine is running.

Check your manual to find what the remaining mileage remaining is (but note this will show a static figure like 1500 - 1700 miles until the remaining Adblue falls below this range). Normally you press the spanner or check button and it should briefly flash up with the figure.

I wouldn't see why the previous owner would have wanted to intervene at this stage with the vehicle being warranted and with this low mileage.

Also, when the engine has been running for a while (ideally at the end of a journey), when the engine is switched off, shut the driver's door and quickly go to the rear of the vehicle. Withing a short while you should hear a whining noise which is the Urea pump sucking back the Urea from the pipes into the tank to prevent it crystalising.

[wurlycorner]

I wouldn't see why the previous owner would have wanted to intervene at this stage with the vehicle being warranted and with this low mileage.

You'd perhaps be surprised - I know people that have removed DPF, EGR etc. on brand new vehicles, regardless of infringing warranty

[dispatch31]

Thank you both for getting back to me on this:

GiveMeABreak - I have checked on the dash and get the warning message (1700miles) and the light on dash for a few seconds. Whenever I have monitored the denox system in DiagBox, I had the engine running and hot. Aside from the lack of adblue pressure indication, I has also noticed that the level of AdBlue is not coming. I realise the tank gets you a long way, but I would expect to see the level coming down (from 16.6litres) after 1000miles of driving since I got the van. I will follow your advise a listen in for the pump emptying the line upon engine stop and report back.

I am with @wurlycorner here, just because the vehicle is still under warranty wouldn't stop someone from getting rid of the system altogether, especially a fleet operator / leasing company if they've already had this problem with many of their vans....

Speak soon,
Arnaud

[PaulC5]

Our cars with Adblue use about 1 to 1½ litres per thousand miles so your level will not have dropped much.

[dispatch31]

Our cars with Adblue use about 1 to 1½ litres per thousand miles so your level will not have dropped much.

Thanks that's useful to know, I will keep an eye on the level reported by OBD, I have another 5 months of warranty, so if by then the adblue is still around 16litres then it clearly isn't working...

[dispatch31]

Hi guys,
If it is of interest I have an update on my adblue situation. To remind you of the context, early January I bought a citroen dispatch originally registered November 2021, with 25,000miles on clock. I have now driven it around 2000miles. I have suspected from the start that the adblue system has been deleted somehow, because all this time the adblue level has not dropped (16.6litres) and the adblue pressure is always at 0bar in Diagbox, but there is no fault.

For the first time today, the adblue pump has started, and ran quite loudly for a good minute, presumably filling the accumulator. Ever since, whenever I stop I have been able to hear a short faint noise coming from the tank that is likely the pump sucking adblue out of the pipe as suggested by GiveMeABreak. I also cannot get the warning and mileage countdown to show when pressing the button on the dash.

I have for weeks now paid very close attention to the adblue tank and pump, so I am absolutely certain this is the first time the system has worked since I bought the van.

Immediately after buying the van, 7 weeks ago, I poured a bottle of "Wynn's Crystal Clean & Protect Car AdBlue Preventative Crystallisation Cleaner Additive - 125ml" as well as 10litres of fresh adblue.

So all I can think off is that over 7 weeks of sloshing around the tank, a possibly crysatlised system was cleaned and started working again. I will connect DiagBox tomorrow to see if I now have pressure and confirm the level comes down over the next 1000miles or so.

Because no error has been reported by the van or DiagBox, I suspect that the adblue stopped working some time ago and someone disabled the ecu fault reporting.

[wheeler]

Is it possible that the adblue system was deleted from the van by the previous owner? Is there a way to tell?

Yes there is, Simply use the van for a year & if you dont get any issues with the system there is a high chance someone has deleted it.

Its unusual that the urea pressure is showing 0, normally with the engine running the system will sit a 4.0 bar then once it activates it jumps up to 5-6 bar.
Have you had someone else drive the van whilst you monitor the readings to see what's happening with the pressure? Its highly unlikely the system will pressurise at idle, the system only only starts working when the engine is very hot & working hard.

[dispatch31]

hi wheeler,
After having looked for weeks in vain for signs of life of the adblue system using DiagBox, it now works, I can see pressure, i can see flow when under load. There is pressure at idle, but there is no flow at idle.

From what I can see, adblue is injected even when the engine is not doing much work, but the flow rate is small. Driving from work with a cold engine (<70deg) and at around 30mph on the flat, there is some adblue consumption, but not much. However, revving the van to 3000rpm on my drive at the end of the same journey, there is no flow as there is little to no load then.

I will now keep an eye on the adblue level, but I have only driven 50miles since the system started working again, so it will be a little while before I see anything on DiagBox.

The big question will be: when adblue fails again, will i get a fault or will it be ignored....

[GiveMeABreak]

The Adblue system really only starts to operate when the engine reaches operating temperature - it serves no purpose otherwise as the temperature in the catalyst is too low for the reaction and conversion to take place.

The accumulator holds pressure at about 6 Bar until the Urea starts to be injected into the catalytic converter, before the pump refills it when the pressure drops to about 5 Bar. So seeing a pressure reading in the diagnostic is no indication that the pump is actually working. May need further investigation with the reservoir off to determine if the pump is working.

[dispatch31]

I am fairly confident the pump is working. When adblue started working again Thursday night, I heard what can only be the pump "loudly" running for 1-2minutes, with engine OFF but ignition ON, as I was parked on side of road after 30miles of twisty road driving. Ever since, the system pressure has gone from 0 bar with engine running hot to 5.5bar at the moment. So I presume the reservoir pickup was blocked by crystallization and when it started flowing again the pump filled the accumulator all the way back to 6bar. The only thing I need to monitor now is the adblue gauge, which has been stuck on 16.6litres for 7weeks, but I am also confident it is OK, as it went from 6litres to 16.6litres when I poured 10L of adblue and the bottle of adblue cleaner.

[wheeler]

So seeing a pressure reading in the diagnostic is no indication that the pump is actually working. May need further investigation with the reservoir off to determine if the pump is working.

Absolutely, it only gives a guide that something is happening when its meant to.
When you do the guided fault finding procedure on Diagbox you need to plumb in a proper analogue pressure gauge as you do it as it gets you to check pressures at different points of the test.