I am still getting the NOX sensor fault and am worried it may go into limp mode. I am happy to buy an aftermarket sensor if it is this at fault but the car just went through its MOT and passed with no problems. The NOX readings are

Downstream SCR -10ppm

Before SCR 106ppm

 

I am no expert on this but this seems to suggest it is working in removing NOX from the system. As I have posted previously the Adblue system can mess up NOX readings and I have had a problem with Adblu where a cable was left disconnected which is now fixed. I wonder if this was a cause? The fault keeps coming back so I need to fix it.

If I need the sensor what is the part number I need to buy?

 

 

6 minutes ago, freddyuk said:

the car just went through its MOT and passed with no problems

MOT does not measure NOx (well not the UK one anyway). Doubt the Ireland equivalent does either, do you have the emissions results printout, if they give such a thing?

 

Or are those numbers from such a printout? Or VCDS, or???

Edited 27 November, 20241 yr by Breezy_Pete

The numbers are from the VCDS. The NCT (MOT) measures "smoke" so they stick the sensor up the exhaust pipe.

 

A bit more info off the VCDS

Voltage after SCR 40800 mV

Voltage before SCR 14400mV

Edited 27 November, 20241 yr by freddyuk
Info

Thought so.

NOx and smoke (particulates) are completely different things.

Not sure I'd spend the money myself, but if you want a part number for the sensor, let me know the VIN.

 

Voltage info above so not sure if these are within spec.

Very odd I had Adblu issue and then this comes up although they seem to have this issue a lot. I am told it will go into limp mode at some point.

I am considering removing and cleaning the sensors although not sure if mine are both in engine bay or underneath.

 

TMBKH7NP1K7013639

Will look up for you tomorrow. 

Do you know what the reading perameters should be? Not sure where I would find this info. That way I can check if the sensor is working but some other issue causing the fault.

No idea on diagnostics for these systems, nor what readings are to be considered normal range.

 

Could try searching web with your engine code as one search input (DFGA).

 

Part numbers that come up are 04L907807AM, superseded by 04L907807EE for one of them.

And 04L907807ES, superseded by 04L907807EG for the other.

Both of the current parts retail at £493 + VAT in the UK.

 

@ApertureS probably knows stuff about this system. 

There will be a Self Study Programme about SCR systems available via erWin, I imagine.

Thanks. Sensor replaced. All fault codes clear. Will see if it comes back. I did not pay £500!

To close out this thread the sensor seems to have cured the problem so far. The replacement sensor was from a well known German discount parts supplier  (in Ireland) and cost euro 160 delivered.

 

@freddyuk Please share the German discount parts supplier. It may help to someone else.

GSF I'd assume

Was this the NOX sensor after the SCR? I replaced mine last year as it started bringng the EML on.

 

I found it hard to find the correct part amongst the aftermarket sensors so ended up not wanting to risk it and bought OEM for piece of mind that it was just going to work.

It was Autodoc. We have trouble getting parts in Ireland at reasonable cost. I also got my waterpump from them delivered to France after I paid the main dealer there €100's more as I was desperate. In a few thousand miles I will be replacing that again so it is here handy!

 

Yes it was the after SCR unit. No coding required.

Edited 3 January, 20251 yr by freddyuk
Add info

Sadly after posting this the EML came back on!! So back to square one we go.......

On 04/01/2025 at 14:52, freddyuk said:

Sadly after posting this the EML came back on!! So back to square one we go.......

 

So the question is.....

 

Is the cheapo sensor reading correct or is there another issue?

Well one option is to fork out £500 for a main dealer supplied sensor and hope it is different to the one I bought. If it does not solve the problem the cost starts to escalate. I am wondering why there is so little feedback from others who must have had the same issue and may have used aftermarket parts.

On 03/01/2025 at 12:22, freddyuk said:

Yes it was the after SCR unit.

What made you think that it was this one that was causing the fault light, rather than the one before the SCR cat?

 

It was the one giving a negative reading.

Was there a fault code relating to it?

Here are two reports - first the latest after replacing NOX sensor and the second is the original before replacement.
I also have the measuring block readings available in CSV format - quite large amount of info....


1 Fault Found:
9571 - NOx Sensor 2 Bank 1
          P22A1 00 [11101100] - Signal too Large
          MIL ON - Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 7
                    Mileage: 110763 km
                    Date: 2024.12.20
                    Time: 12:57:26

                    Engine RPM: 1254.00 /min
                    Normed load value: 0.0 %
                    Vehicle speed: 29 km/h
                    Coolant temperature: 76 °C
                    Intake air temperature: 53 °C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.720 V
                    Unlearning counter according OBD: 40
                    NOx sens.dwnstrm.SCR cat conv: NOx conc.: 2459 ppm
                    NOx sensor before SCR cat conv: NOx concentration: 12 ppm
                    NOx sens. dwnstrm. of SCR cat.: target heat. temp reached-Bits 0-7: 1
                    NOx sensor after SCR catalytic converter: supply voltage: 14560 mV
                    NOx sensor before SCR catalytic converter: supply voltage: 14400 mV
                    Outside temperature sensor 1: B1: raw value: 11.5 °C
                    Mean injection quantity: 0.00 mg/stroke

 

1 Fault Found:
9560 - NOx Sensor 2 Bank 1 Voltage Suppy
          P220B 00 [11101101] - Electrical Malfunction
          MIL ON - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 6
                    Mileage: 108999 km
                    Date: 2024.10.19
                    Time: 13:42:17

                    Engine RPM: 1501.50 /min
                    Normed load value: 68.2 %
                    Vehicle speed: 60 km/h
                    Coolant temperature: 83 °C
                    Intake air temperature: 65 °C
                    Ambient air pressure: 1000 mbar
                    Voltage terminal 30: 14.760 V
                    Unlearning counter according OBD: 40
                    NOx sens.dwnstrm.SCR cat conv: NOx conc.: -10 ppm
                    NOx sensor before SCR cat conv: NOx concentration: 74 ppm
                    NOx sens. dwnstrm. of SCR cat.: target heat. temp reached-Bits 0-7: 0
                    NOx sensor after SCR catalytic converter: supply voltage: 37600 mV
                    NOx sensor before SCR catalytic converter: supply voltage: 14560 mV
                    Outside temperature sensor 1: B1: raw value: 14.5 °C
                    Mean injection quantity: 14.69 mg/stroke

Edited 8 January, 20251 yr by freddyuk

An update on this issue for anyone with similat NOX issues.

 

I have had great help from one poster on the Rosstech forum who schooled me on using the inner workings of the VCDS.

I will replicate my readings here which I took today. We think the new sensor IS working after all . I am getting readings on both NOX sensors.

 

 

moving log 19th.csv

imo it would have been better to have gotten the whole adblue system  coded out, normally along with a remap.

adblue systems are even more problematic than dpf and egr valves 

I have read about this but we are not all capable of fiddling around inside the ECM. I am learning but not ready for that yet.

Hi I have the same problem with my skoda superb the nox sensor whats the location of the sensor is it the one on top of the dpf and also where can I get the vag diagnostic tool if someone can point me in the right direction please