Citroen GP and P20EE DTC (NOx)

[kuhar]

So, before I go and by a new NOx sensor and potentially a new injector, I just wanted to ask if anyone has a different opinion on what is happening.
Car: Citroen GP 2.0 BlueHDI (2015).

A month ago I had my DPF filter cleaned. The person cleaning said that the NOx sensor might fail in the future (why? I have no idea... Does sensor get removed or what when cleaning a DPF?). The ECU was notified new DPF filter was installed and that was it.

Yesterday I was running cca 120 km/h and after like 5 mins got the Engine Fault: Have the vehicle repaired and Urea: Emissions control fault lights on. The automobile didn't lose power or anything.
Diagnostic showed one error:

P20EE 00 Depollution of the deNOx system
Cause Local
Status Permanent
Characterisation of the fault Emission control ineffective

Temperature outside was below 0°C and the car was completely warmed up (at least when the error popped up).
- Temperature of the deNOx catalytic converter was at 314 °C
- Pressure of the urea fluid was at 5.44 Bar

So, I searched the forum and one similar thread shows new sensor might be needed (and maybe an injector too), but my question is whether there is something else going on? Might be the temperature outside that caused the fault? Didn't notice crystallisation at the exhaust pipe, but then it was night and my vision is crap, I'll check again today.

[GiveMeABreak]

For this fault code on this vehicle the official recommendation is to follow the fault finding and guidance on the diagnostic:

It is compulsory to carry out diagnostics using the diagnostic tool in internet connected mode, with compulsory identification of the technician: Select the "Fault finding" menu . Carry out the "reading of fault codes".

At the end of the global test, wait for the Diagnostics tab to start up (home screen with selection of methods by domain). Quit the Diagnostics session, returning to the home tab . Validate the message "Do you wish to quit the current session?"

For this fault code, it is important to use the guided diagnostics present in the diagnostic tool.

[kuhar]

I did get the code from 9.91 Diagbox (clone, not connected) and no other codes were present, but what you are saying is that a visit to an official Citroen shop should be made because of the internet connected mode is needed? Damn...

[GiveMeABreak]

The technical service bulletin lists no action or repair - only to follow the diagnostic guidance in internet connected mode, so that would be the case to troubleshoot further.

[kuhar]

So to continue...

Also received the error (last time I DIDN'T delete the P20EE 00 error):
P2BAD 00 Depollution of the deNOx system
Cause Local
Status Permanent
Characterisation of the fault Failure of the system

and Urea: Emissions control fault where word Urea was in a red background, became yellow background and additionally Urea blinking light appeared at the bottom of the dashboard. So many lights

As I said, it was cold around here, below 0°C so I believed maybe NOx sensor was faulty, but actually it seems it was working correctly. Urea yellow flashing light was of course a clue. What I think happened is that some of the Adblue crystallized and the rest left in the solution was not enough to completely deNOx the exhaust gases. Therefore NOx sensor reported higher concentration of the NOx.
So, I calculated how much Adblue the car might have consumed in 8000 km. The online calculator said around 7 liters (when I bought it 8000 km ago, I've put 10L in the tank). So, I deleted all the errors, took another 10L of Adblue, put it in the tank, gave contact for 10 seconds, then started the car.

I've driven the car now for 100 or so kilometers and it seems all is good. No errors. Fingers crossed.

[kuhar]

After 1000 km, again Check Engine and Emissions control fault where word Urea was in a red background. After driving for another 50 km, Check Engine stayed, but Urea on red background vanished -> Yellow blinking Urea message appeared with 1100 km till shutdown message. OK, something is definitely going on, especially when I've put 10L of Adblue 1000 km ago. So it definitely has Adblue. Nothing, to to trusted mechanic.

Error, the same, P20EE and P2BAD. He said it's not crystallization and continue to reinitialize the pump of whatever is responsible for Adblue injection. He says, water float or sensor or w/e gets confused and it's best to reinitialize the pump (if it is working) so that the car's ECU starts from scratch. So, after re-initializing the pump, yellow Urea message disappeared (no error code was deleted at that time, only after).
Also, suggestion is to fill the adblue reservoir to to cap/rim and to use adblue additives against crystallization.

We'll see how it goes from here...

[GiveMeABreak]

Yes that's good advice as far as using an Adblue Cleaning and anti Crystallisation additive. I've just put some in and filled my tank using this Wynn's:

The next 10 litre container of Adblue I buy, I will just put in a bottle of the Wynn's directly into it and then it's already in the mixture when I top the tank up every 2 months. Forte also do an Adblue additive.

These can keep the Adblue injector free of crystal build up too it is claimed.

[sakata911]

After 1000 km, again Check Engine and Emissions control fault where word Urea was in a red background. After driving for another 50 km, Check Engine stayed, but Urea on red background vanished -> Yellow blinking Urea message appeared with 1100 km till shutdown message. OK, something is definitely going on, especially when I've put 10L of Adblue 1000 km ago. So it definitely has Adblue. Nothing, to to trusted mechanic.

Error, the same, P20EE and P2BAD. He said it's not crystallization and continue to reinitialize the pump of whatever is responsible for Adblue injection. He says, water float or sensor or w/e gets confused and it's best to reinitialize the pump (if it is working) so that the car's ECU starts from scratch. So, after re-initializing the pump, yellow Urea message disappeared (no error code was deleted at that time, only after).
Also, suggestion is to fill the adblue reservoir to to cap/rim and to use adblue additives against crystallization.

We'll see how it goes from here...

Hello,

Did you managed to find the root cause, as I am in perfectly the same situation - I have checked the NOX sensor with DiagBox and it seems to be working just fine, also I have successfully done the UREA Pressure test - 50ml ADblue was injected, the EGR also seems to be ok, the DPF differential pressure is at 0.003mbar at idle, so it seems it is also not blocked....
I have tried to re-initiate the Denox system, but that didnt changed anything
The strange for me is, that I can not clear the faults when the car is hot (The codes are re-written even the car is only on ignition), I only can clear them only after the car has cooled down, so could it be a temperature sensor?

Except P20EE and P2BAD no other codes are presented....

Thank you in advance for the help!

[kuhar]

The root cause in the end was the faulty adblue tank. Actually, it was a faulty NOx sensor which can't be repaired or bought new, you have to buy the whole bloody adblue tank.
The options were to buy a new one from dealership, cca €1000 (2 year warranty), to buy a refurbished one with 1 year warranty @ €700 (I think a local firm sources this from a factory in Poland) or to play with the ECU @ €125. I chose the latter option and now it works as it should at the cost of additional NOx in the exhaust...

[GiveMeABreak]

The NOx sensor is available separately (8) in the diagram, so not sure why you would think they're not? Just thought I'd chip in here in case the OP didn't think they were available.

[kuhar]

Wow, thanks, it seems I should've asked here (you Marc) and not believe the words of the authorized dealership...
They said the sensor was at fault and that the whole tank should be taken out. It might be that something else was broken/malfunctioning too, but they stated only the NOx sensor was out.

[GiveMeABreak]

I suppose it depends on what else they found, and there may well have been a problem with the tank additionally, but they should of at least told you that the NOx sensor itself is replaceable.

[userAL]

In my case, with this "P20EE 92" error, official service claimed catalyst problem, billed me for 2k euro, changed catalyst with adblue injector.
I asked several times about adblue tank, but they was quite confident that it's catalyst.

Mileage: 65500km only.

[GiveMeABreak]

Thanks for sharing your experience - will be interesting to see if this cured the issue. I'm more inclined to suspect crystallisation around the Urea Injector - which if left uncleared will of course lead to further internal blockages - which may be why they changed the complete assembly.

[userAL]

I can add more info.
So, the very first time when this error appeared was in January 2024, while i had just 46 thousands kilometers.
Engine fault. Emission fault, starting impossible in 1100km.
Official citroen service said it is catalyst and adblue injector.
But, since there were no catalyst spare parts at that time, they changed in February only injector adblue and cleared errors. It was cost me about 250 EUR.

I can also say, that after February I've started refueling adBlue more carefully, add fresh liquid (by checking the date of manufacture) and add only 5-10 liters when it was asked, to avoid crystalization.

It helped for 10 months.
Till 22.11.2024 when this error appeared again.
Just in case: the outdoor temperature is quite good, from +5?C at night and upto +16?C in sunny day for the last month. In October it was +10..+24?C. So, as you might understand, there is no reason for crystalization by temperature at all.

This time, at 4.12.2024 they replaced catalyst and injector adblue, blaming me that it was my decision to replace only injector in January.
Nevertheless, there are no errors since 4.12.2024

BTW: i started to add Wynny's adblue thing, hopefully new catalyst and this additive will help me to completely avoid this problem.