SCR efficiency too low

Hi,

I'm still experiencing the following issue, see the log.
3 error messages with the SCR system.

My current diagnosis:

Cables and wires, okay (visual inspection).

SCR tank almost full, refilled a few weeks ago, but the vehicle had been parked for almost a year before I started using it again, so the remaining fuel in the tank was quite old.

The level indicator is working. The remaining range based on mileage has decreased from 8500 km to 7900 km due to recent trips, so I believe AdBlue is being injected. The pressure is at 5500-6300 mbar.

Supplier for quality reduction measures: Validity: Invalid.
Supplier for quality reduction agents: Quality: 0.0%


The injector valve was removed and cleaned in a hot ultrasonic bath. However, I didn't see any crystallization, but it seemed to be dirty/oily.

The valve actuator diagnosis indicates a fine spray mist, but I have no idea how much it should be.

Temperature at the injector nozzle: between 35 and 60°C.

NOx Sensor: The measured NOx concentration is almost zero ppm during acceleration, and increases to 914 ppm during normal driving. The O2 concentration also changes its values depending on the load conditions.


Possible sources of error: AdBlue fluid, quality sensor, pump unit, injector valve, NOx sensor.


What do you think about that?

What's the best way to proceed?

Thank you for your help.

Quote:

33005 - Sensor 1 for NOx Bank 1. P2201 00 [01100100] - implausible signal. Sporadically - unconfirmed - checked since last deletion. Environmental conditions: Error priority: 2 Error frequency: 1 Mileage: 180,135 km Date: 2026.07.01 Time: 16:13:41 Motor speed: 1100.25 rpm. Normalized load value: 0.0% Vehicle speed: 53 km/h Coolant temperature: 85 °C Intake air temperature: 25 °C Atmospheric pressure: 990 mbar. Voltage at terminal 30: 14.109 V. Lost count after OBD: 40 Air mass at air mass flow sensor 1: 39.6 kg/h. Average injection volume: 0 mg/stroke. Exhaust Gas Recirculation (EGR) Valve, Bank 1: Stored Fault Code - Live Value: 38.11 % Air mass sensor 1 bank 1 air mass: Raw value: 300.7 mg/stroke. NOx sensor upstream of SCR catalyst: NOx concentration: 0 ppm. NOx sensor after SCR catalyst: NOx concentration: 127 ppm. NOx sensor upstream of SCR catalyst: Activation status offset diagnosis: not active. NOx sensor before SCR catalyst: Supply voltage: 0.000 V NOx sensor upstream of SCR catalyst: Offset correction factor: 0 ppm. NOx sensor upstream of SCR catalyst: O2 concentration: 0.0000. NOx sensor after SCR catalyst: Activation status, offset diagnosis: active. NOx sensor after SCR catalyst: Supply voltage: 13.421 V. NOx sensor after SCR catalyst: Offset correction factor: 121 ppm. NOx sensor after SCR catalyst: O2 concentration: 0.0230

Hello,

Is that normal? Check the extended measurement data blocks and the circuit diagram (or examine them) to see if there's a sensor that needs to be powered.

Sure, here's the translation:

"LG" translates to "Best regards" or "Sincerely" in English.