It’s a brand spanking new NOx 1 sensor. Does this mean it’s defective? Or a problem with the Sense Circuit for Heater for NOx Sensor 1?


Thursday,12,June,2025,10:12:04:46737
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 25.3.1.2 (x64) HEX-V2 CB: 0.4671.5
Data version: 20250604 DS365.0
www.Ross-Tech.com

Dealer/Shop Name: MOON

VIN: XXXXXXXXXXXXX9703 License Plate: xxx3645
Mileage: 154039 Repair Order: OL2C007



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Address 01: Engine Labels: 059-907-401-V2.clb
Control Module Part Number: 4L2 910 401 HW: 4L0 907 401 D
Component and/or Version: 3.0TDI FSA H18 0009
Software Coding: 2A2A4012253600050000
Work Shop Code: WSC 03993 002 1048576
ASAM Dataset: EV_ECM30TDI0114L2910401 002008 (AU56)
ROD: EV_ECM30TDI0114L2910401_002.rod
VCID: 61987B57D1C2C312E07-8034
6 Faults Found:

9574 - NOx Sensor 1 Bank 1
P2200 00 [00100000] - Electrical Malfunction
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 247800 km
Date: 2025.06.06
Time: 15:28:39

Engine speed: 779.50 /min
Normed load value: 48.2 %
Vehicle speed: 0 km/h
Coolant temperature: 88 �C
Intake air temperature: 35 �C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 14.120 V
Unlearning counter according OBD: 37
Engine status: COENG_RUNNING
Engine status-Test_Program_Co Eng st COMPU VERB UBYTE: 3

9879 - Sense Circuit for Heater for NOx Sensor 1 Bank 1
P2209 00 [00100000] - Implausible Signal
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 247838 km
Date: 2025.06.06
Time: 18:22:54

Engine speed: 778.00 /min
Normed load value: 61.6 %
Vehicle speed: 0 km/h
Coolant temperature: 89 �C
Intake air temperature: 49 �C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 14.080 V
Unlearning counter according OBD: 39
NOx sensor 2: NOx concentration: 0 ppm
NOx sensor 1: NOx concentration: 0 ppm
Target value of heating temperature of NOx sensor 2-Bits 0-7: 0
NOx sensor 2: feed voltage: 0 mV
NOx sensor 1: feed voltage: 13440 mV
Outside temperature: 33.0 �C
Mean injection quantity: 10.31 mg/stroke

30865 - NOx Sensor 1 Bank 1
P2201 00 [01100000] - Implausible Signal
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 2
Mileage: 247833 km
Date: 2025.06.06
Time: 17:35:07

Engine speed: 828.00 /min
Normed load value: 23.1 %
Vehicle speed: 15 km/h
Coolant temperature: 89 �C
Intake air temperature: 33 �C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 14.000 V
Unlearning counter according OBD: 39
Accelerator pedal travel: 0.00 %
Accelerator pedal: sensor voltage 1: 737.8 mV
Accelerator pedal: sensor voltage 2: 371.2 mV
Accelerator pedal: switch positions-Bits 0-7: 9
Starter control: Interlock- or P/N-signal-Bits 0-7: 1
Limitation: torque: 187.0 Nm
Control Module temperature: 46.9 �C

30867 - NOx Sensor 1 Bank 1
P2201 00 [01100000] - Implausible Signal
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 2
Mileage: 247833 km
Date: 2025.06.06
Time: 17:35:07

Engine speed: 828.00 /min
Normed load value: 23.1 %
Vehicle speed: 15 km/h
Coolant temperature: 89 �C
Intake air temperature: 33 �C
Ambient air pressure: 1000 mbar
Voltage terminal 30: 14.000 V
Unlearning counter according OBD: 39
Accelerator pedal travel: 0.00 %
Accelerator pedal: sensor voltage 1: 737.8 mV
Accelerator pedal: sensor voltage 2: 371.2 mV
Accelerator pedal: switch positions-Bits 0-7: 9
Starter control: Interlock- or P/N-signal-Bits 0-7: 1
Limitation: torque: 187.0 Nm
Control Module temperature: 46.9 �C

26253 - NOx Sensor 1 Bank 1
P2201 00 [11101101] - Implausible Signal
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 247776 km
Date: 2025.06.05
Time: 13:48:12

Engine speed: 1527.50 /min
Normed load value: 82.0 %
Vehicle speed: 76 km/h
Coolant temperature: 89 �C
Intake air temperature: 38 �C
Ambient air pressure: 1010 mbar
Voltage terminal 30: 14.060 V
Unlearning counter according OBD: 40
Accelerator pedal travel: 26.11 %
Accelerator pedal: sensor voltage 1: 1485.6 mV
Accelerator pedal: sensor voltage 2: 728.0 mV
Accelerator pedal: switch positions-Bits 0-7: 1
Starter control: Interlock- or P/N-signal-Bits 0-7: 0
Limitation: torque: 231.8 Nm
Control Module temperature: 53.1 �C

26255 - NOx Sensor 1 Bank 1
P2201 00 [11101000] - Implausible Signal
MIL ON - Intermittent - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 3
Mileage: 247781 km
Date: 2025.06.05
Time: 15:18:20

Engine speed: 1195.00 /min
Normed load value: 0.0 %
Vehicle speed: 49 km/h
Coolant temperature: 87 �C
Intake air temperature: 38 �C
Ambient air pressure: 1010 mbar
Voltage terminal 30: 14.140 V
Unlearning counter according OBD: 40
Accelerator pedal travel: 0.00 %
Accelerator pedal: sensor voltage 1: 737.8 mV
Accelerator pedal: sensor voltage 2: 371.2 mV
Accelerator pedal: switch positions-Bits 0-7: 9
Starter control: Interlock- or P/N-signal-Bits 0-7: 0
Limitation: torque: 129.6 Nm
Control Module temperature: 48.4 �C


Readiness: N/A

 

Probably just a loose connector not locked into place given so many codes related to it, so check that you made a solid connect and it 'clicked' into place. Also, remember whenever you disconnect anything on a Q7 to always go check for fault codes once everything is reconnected again, then clear all the fault codes so it won't confuse you to see those later or have any negative impact on the car...like a limp mode, etc.

If there's anything you wanna mention about the sourcing of the NOx sensor, now's the time. There's also two of them, one upstream of catalyst/DPF, etc., and one downstream post reductant catalyzer/catalyst, so be sure you replaced the correct one. From what I see on scan this is the sensor 1, which is right there at rear of engine between turbo & catalyst, next to the O2 sensor, etc.

 

yeah, thanks. I’ll recheck the connection.

got it here: https://ebay.us/m/326KMZ with 5 yr warranty.

In an Audi Q7, the two NOx (Nitrogen Oxide) sensors are typically located in the exhaust system. The first sensor (NOx sensor 1) is situated near the turbo downpipe, measuring engine-out NOx levels. The second sensor (NOx sensor 2) is positioned after the selective catalytic reduction (SCR) catalyst, monitoring the NOx levels exiting the catalyst.

Detailed Explanation:

• NOx Sensor 1:
  This sensor is located closer to the engine, typically within the exhaust manifold or near the turbocharger. Its primary function is to measure the amount of NOx being produced by the engine before it enters the SCR system.
• NOx Sensor 2:
  This sensor is placed after the SCR catalyst, which is a component designed to reduce NOx emissions. Its purpose is to assess the effectiveness of the SCR system by measuring the remaining NOx levels after the catalytic process.

Essentially, NOx sensor 1 provides a baseline reading of engine-out NOx, while NOx sensor 2 indicates how well the SCR system is working to reduce these emissions.

 

More or less, but they are integrated with the SCR system so it knows how much reductant solution to spritz into the exhaust.

 

My inspection is a month overdue and I've replaced NOx 1 twice only to get the same result from two new sensors. I'm guessing it's not the sensor but possibly a wiring fault. Any suggestions?

Address 01: Engine Labels: 059-907-401-V2.clb
Control Module Part Number: 4L2 910 401 HW: 4L0 907 401 D
Component and/or Version: 3.0TDI FSA H18 0009
Software Coding: 2A2A4012253600050000
Work Shop Code: WSC 03993 002 1048576
ASAM Dataset: EV_ECM30TDI0114L2910401 002008 (AU56)
ROD: EV_ECM30TDI0114L2910401_002.rod
VCID: 61987B57D1C2C312E07-8034
2 Faults Found:

26253 - NOx Sensor 1 Bank 1
P2201 00 [11101101] - Implausible Signal
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 249452 km
Date: 2025.07.29
Time: 19:51:55

Engine speed: 1618.50 /min
Normed load value: 71.8 %
Vehicle speed: 67 km/h
Coolant temperature: 88 °C
Intake air temperature: 36 °C
Ambient air pressure: 1010 mbar
Voltage terminal 30: 14.020 V
Unlearning counter according OBD: 40
Accelerator pedal travel: 25.13 %
Accelerator pedal: sensor voltage 1: 1456.4 mV
Accelerator pedal: sensor voltage 2: 713.4 mV
Accelerator pedal: switch positions-Bits 0-7: 1
Starter control: Interlock- or P/N-signal-Bits 0-7: 0
Limitation: torque: 256.4 Nm
Control Module temperature: 47.4 °C

27264 - NOx Sensor 1 Bank 1
P2201 00 [01100100] - Implausible Signal
Intermittent - Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 249525 km
Date: 2025.08.01
Time: 11:49:46

Engine speed: 1709.50 /min
Normed load value: 0.0 %
Vehicle speed: 103 km/h
Coolant temperature: 86 °C
Intake air temperature: 25 °C
Ambient air pressure: 1010 mbar
Voltage terminal 30: 14.260 V
Unlearning counter according OBD: 40
Accelerator pedal travel: 0.00 %
Accelerator pedal: sensor voltage 1: 733.0 mV
Accelerator pedal: sensor voltage 2: 371.2 mV
Accelerator pedal: switch positions-Bits 0-7: 9
Starter control: Interlock- or P/N-signal-Bits 0-7: 0
Limitation: torque: 316.1 Nm
Control Module temperature: 33.7 °C


Readiness: 1 1 0 0 0

 

The Sensor 1 for NOx has that odd wiring interface far away on its' lonesome on right side of engine bay midways (Driver's side on LHD car), so yeah, you gonna have to trace the harness back to the ECU to look for any odd spots in the wire or rodent damage possibly.

I'd give it a quick glance-over from the wiring connector, after verifying the connection from harness side is pinned solid, using a strong light, but I'd bet the issue will be closer to the ECU connect point. Seems like most of the unexplained odd codes/symptoms are turning out to be wire damage or related to water getting in the ECU, etc. There's been a fair few rodent damaged wiring issues that have been popping up on this forum in the past year.

Keep us informed! Good luck.