Hello, I was brought to the workshop this type with 39,000km year 2019 engine code 55280444, with Adblue failing and Engine failure light on, the customer stated that he had topped up the adblue to full 2 days ago, however in engine management diagnosis errors 0, while of the dosage module I get the following error codes:

P2BA9 : NOX concentration too high - Adblue concentration too low
P2BAF : NOX system in emergency (failure warning on)

Removing the errors leaves P2BAF while P2BA9 returns shortly afterwards

I checked the system pressure and it comes to 5.9 bar

Tried to bleed via diagnostics tester

Tried resetting tank level and resetting Syst. Adblue dosage.

Tried a test run but nothing changed

Checked the parameters measured by the two NOX probes:

Upstream fluctuates between 80 and 160 ppm, depending on engine speed
downstream constant measurement 0

The injector has slightly occluded nozzles (not from adblue crystallisation but from soot) this afternoon I'll try a cleaning after which I might try draining the adblue in case the one present is not of suitable quality.

Do you have any advice on what other checks to make?