Ad blue again

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Ad blue again

Post by Harrythephot »

Hi all. I've had the dreaded adblue issues and have been trying to diagnose them.

I thought it was likely the tank or the supply tube to the injector, or maybe the Nox sensor.

Removed cleaned and tested urea injector with water pump and 9v battery.

Removed and cleaned Nox sensor.

I have just received a new working Lexia and ran the emissions system tests.

I could hear the Adblue injector operating during the Urea injector test.

And for the 1st time, I could hear the Adblue pump operating.

Most of the emission system tests ran fine, with the exception of one module, returning the error

"Excessive pressurisation of the urea gauge pump module"

I had wondered if it could be a blocked supply tube.

Running the Denox flow rate test failed with

"Test interrupted Injection not authorised"

But when I unclipped the Urea pipe from the urea injector and ran the test, I got lots of fluid out of it.

Great. Hose is not blocked and pump appears to work.

Connect it back onto the injector, run the test and.......Nothing.

So the injector is not opening when the Denox flow test is done.

But I heard it trigger when the urea injector test was done.

I had also bench tested the injector with water pressure and a 9v battery and it produced jets of water.

What am I missing?

The injector clicks during the injector test, but then doesn't work during the flow test.

What "authorises" the injector to function?

Tomorrow I will test for voltage to the injector, but beyond that I'm stumped.
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Re: Ad blue again

Post by GiveMeABreak »

That's all done by the engine ECU - which is what is suppling you with the data from your diagnostics.

I would be thoroughly checking where the injector is housed - inside the port to make sure that is not full of crystallised Urea. See below - sometimes the blockage is past the injector and in the Cat.
adblue crystals.PNG
Whew you do get it resolved - I strongly suggest you start using some Wynn's / Forte Adblue Additive to help clear and prevent crystallisation in future.
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Re: Ad blue again

Post by Harrythephot »

Thank you for the reply.
I've already removed and cleaned the injector, plus bench tested it with a water pump and a 9v battery to prove that it was still functioning.

The diagbox test on the injector passes and makes it click rapidly.
The diagbox test on the flow fails and does not trigger the injector (not authorised), but does pump water if the hose is disconnected.

I initially thought the dash warnings would be a dead pump, or maybe a blocked supply hose, but both appear to be working.

If it wasn't an MOT failure, I would just ignore it.

I've handed it over to a garage now as I'm unable to reconcile a working injector, with one that doesn't function when connected to the system.

If I can hopefully get this issue fixed, I may well try to find an older model, without this complex rubbish on it.