NOx signal too low

Could someone please explain the error to me?

Code:

Adresse 01: Motorelektronik Labeldatei: DRV\059-907-401-V2.clb Steuergerät-Teilenummer: 4G0 907 589 F HW: 4G0 907 589 B Bauteil und/oder Version: 3.0BTD EDC17 X23 0008 Codierung: 122A403A257603030000 Betriebsnummer: WSC 92521 052 00000 ASAM Datensatz: EV_ECM30BTD0114G0907589F 001008 (AU57) ROD: EV_ECM30BTD0114G0907589F_001.rod VCID: 377B45848EC48F2933-8062 1 Fehler gefunden: 9691 - Geber für NOx (G295) P1033 00 [10101111] - Signal zu klein Warnleuchte EIN - bestätigt - geprüft seit letzter Löschung Umgebungsbedingungen: Fehlerpriorität: 2 Fehlerhäufigkeit: 1 Kilometerstand: 123985 km Datum: 2024.06.04 Zeit: 06:16:18 Motordrehzahl: 1386.00 /min Normierter Lastwert: 91.0 % Fahrzeuggeschwindigkeit: 86 km/h Kühlmitteltemperatur: 93 °C Ansauglufttemperatur: 14 °C Umgebungsluftdruck: 980 mbar Spannung Klemme 30: 14.380 V Verlernzähler nach OBD: 40 Luftmasse: Istwert (mg/Hub): 473.6 mg/stroke NOx Emission NOx-Sensor 2: 132 ppm NOx Emission NOx-Sensor: 41 ppm Berechnete NOx-Konzentration hinter Turbolader: 172 ppm Ventil für Abgasrückführung: Istwert: 86.51 % Mittlere Einspritzmenge: 24.31 mg/stroke Außentemperatur: 11.0 °C Readiness: 1 1 0 0 0

Hello,

Did the error occur after a long drive (over 100 km) with very little load, for example, driving on the highway at 90 km/h?

I'm experiencing a similar problem with my T6, but I haven't been able to find a definitive cause yet. My suspicion is that it might be related to soot buildup/a low temperature of the NOx sensor, or simply its aging.

I would first fill up the SCR tank, clear the error codes, and see if the error reappears.

Best regards, Rainer.

The error is recurring, and it initially appeared after about a week, but now it appears after only a day, even after cleaning the sensor. Since the time it takes for the cleaning cycle to complete has decreased, I suspect a faulty sensor and will have it replaced.

top55 wrote:

The error is recurring, and it first appeared about a week ago, and now, after cleaning the sensor, it appears after only a day. Since the time after the cleaning has decreased, I suspect a defect in the sensor and will now have it replaced.

Thank you for the information. Feedback on whether this is correct is very welcome!

The weasel had gnawed on the cable at the front sensor, causing the error .

Where is the front sensor located on your device? Is there an NOx sensor installed before the AdBlue injection valve?

If no cost-saving measures were implemented, then there are at least two sensors, because otherwise, it's only possible to check whether the system is functioning correctly using the estimated value and the value obtained after the AdBlue injection. The front sensor in the A6 Competition is located under the water reservoir and measures the raw exhaust gas.

Currently, while reading the log, I'm getting a clearer picture, and it's quite evident what's happening. Since the second sensor measures more than the first, it's likely the first sensor that's the problem, because the NOx value shouldn't be higher at the rear than at the front, especially since the calculated value behind the turbocharger is higher than the actual reading at the rear .

dieselschrauber wrote:

Where is the front sensor located on your device? Is there a NOx sensor before the AdBlue injection valve?

As of my knowledge from 2022, only one truck manufacturer, as well as Venturi Motori with some RDW 3.0-liter diesel engines, omit the front sensor.

When purchasing a replacement, it's important to pay attention to the correct part number, because even though the NOx sensors often fit physically, they operate on different CAN node numbers and/or SPNs (Standard Parameter Numbers) depending on whether they are located at the front or rear of the vehicle.

Regards,

Bo.