DS4 2.0 blue hdi faulty deNOx system

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shedman
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DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

My ds4 2015 has just developed a fault with the deNOx system, the adblue light, service light and engine management light are all illuminated. Scanned the car with Lexia and pulled the following 3 codes.
U029D. fault in communication with the deNOx system. ( no communication)
P2BAD. Depollution of the deNOx system. ( failure of system)
P2200 . NOx sensor ( component detected not communicating on the emission control network)
Due to these faults which are permanent the vehicle is on countdown 650 miles left.
Am I right to assume the NOx sensor is the culprit, if this is so are both sensors the same parts numbers, I have been able to get the numbers from the rear NOx sensor the front sensor is a totally different ball game I can feel the probe in the cat but loose the wires around the rear of the engine.,
Regarding P2BAD when looking at description of the code one thing that stands out is the NOx %, the content downstream of the deNOx catalytic converter is 20 ppm, upstream the NOx % content is 32767 ppm, does this seem right.
Hopefully someone can shed a light on this issue.
Shedman.

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by RichardW »

It does sound like it - but these early systems can develop an issue with the pump/tank, but this looks like it has a specific fault code. Does it indicate which sensor is faulty? If you look at the live data are one or both of them moving as the engine revs change? It looks like there are different part nos for the different sensors - neither of them is cheap....

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by GiveMeABreak »

Pop your VIN up and I can check whether there is anything outstanding on the vehicle.

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shedman
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

vin number is VF7**************[VIN obfuscated, can be read by forum staff]
The rear NOx sensor is made by continental 9678570780 / 5wk96746a these retail at around £250 but as you say will have to check live data to hopefully find which sensor has given up,but as stated earlier I have found the probe but the wire goes around the back of the engine and is lost as can neither see or feel the control unit.
The Urea tank in the past has had the modified cap fitted, I was fully expecting the pump fault code logged but thankfully not.
Shedman.

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GiveMeABreak
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by GiveMeABreak »

Hi Shedman

Thanks for your Forum donation.

Ok, so that part number (8) on the diagram below was the original number and has now been been superseded by: 9821120980. The modified part costs £324.36 inc. VAT from Citroen as of today. The older sensor was priced at £262.48.

Item (3) is the exhaust gas temperature sensor.
Item (6) is your Particle Filter Pressure Pipe.
image_2021-02-15_114641.png
There are no outstanding after-sales campaigns showing and although I do have specific TSBs for faults codes relating to the UREA system concerning the NOx sensors - none of those are the same as the ones you posted.

shedman
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

Marc, thanks for the information. The diagram explains why I could not find the control box for what was thought to be a NOx sensor in the cat, they are double exhaust gas temperature sensors, the only NOx sensor is at the rear of the particulate filter which is a lot easier to get at.
The continental 9678570780 / 5wk96746a which is at the moment fitted, is there any gain by fitting the 9821120980 and will this require a software update or just learned via Lexia. One thing that was noticed on the NOx sensor was the silicone sleeve which covers the top of the probe and wires had been pulled off the probe so wide open to the elements.
Shedman

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GiveMeABreak
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by GiveMeABreak »

The replacement part is very likely to be different and as a result of improvements due to issues, so I always recommend the latest part if replacing.

There's a new one here for just over £200 - might be worth a look - new part number.

https://www.ebay.co.uk/itm/254861475374

It is very likely that the new unit will need initialising when replaced as it does require this on my Aircross.

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by wheeler »

DeNOx faults are a pain in the back side and the fault codes are generally not very helpful most of the time. There is a checking process for the whole system to get to the bottom of the fault that involve checking the urea pump is pressurising and checking the flow of the urea injector. Faults with these can make the NOx sensor read incorrectly. The NOx sensors do fail but without doing other checks its just a bit of a guess. As you have P2200 I would check the power supply & CAN signals at the sensor. There are 4 wires on the plug for the sensor, With the engine running & sensor connected Measure the voltage across the 2 outer pins, you should get battery voltage. Next measure the voltage of the 2 inner wires individually between the wire & earth, these are the CAN wires, you should get around 2.5v on each, you may get slightly different voltages on each of these wires but both should add up to around 5v. You will need needle back probes or improvise something similar on your meter.
They system does need re initialised afterwards & told a new sensor is fitted.
Just be aware too that he sensors can be very stubborn to remove, they often need heat & the threads in the exhaust re tapping afterwards.

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

Marc & Wheeler thanks for the advice, new NOx unit ordered 9821120980 got it of a guy on ebay for £180 which I thought was a good price supposed to be genuine continental peugeot / citroen part but will see when it is delivered. Is initialising the system an easy job with diagbox I am using version 9.68 which was purchased from Jim @ easydiagnostics .
Shedman

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by GiveMeABreak »

I can't help you with calibration Shedman - there's very little on what is involved and each system may vary. It may be something you can find in one of the repair menus, or run a Global Test and see if you can identify the NOx sensor ECU from the list after the test has finished, then that may provide a menu for calibration or configuration.

wheeler
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by wheeler »

Yes its a simple process, once you are in the injection menu go into pack repair > replacement parts > emission control > replacement of the NOx sensor. Followi the guided prompts.
After that do renitialisation of the de NOx system, from memory its in the same menu.

shedman
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

Brilliant thanks for that I will give it ago when the sensor arrives. I have just laid the car up for the moment until part arrives and travelling with my son to work but he will soon get sick of that 😂
shedman

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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

An update on the NOx system faults, got the replacement NOx sensor today and have fitted it after work, Wheeler you were right about how tight and stubborn they are to get out do they put thread lock on them when installed 😖 proprietary lambda sockets would not even look at it just flexing and springing off. All fault codes cleared with diagbox and the mileage countdown has gone the only issue is when installing replacement NOx sensor in diagbox it is saying faults present and quits, reinitialisation of the NOx system completes ok.
All ecu,s checked for fault codes and all are clear.
Any ideas.
Shedman.

wheeler
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by wheeler »

No they dont thread lock them, they actually come pre greased. All it really does is make it run in easier though.
If the fault codes & countdown has gone I would just wait & see what happens, nothing else you can really do unless the warning comes back on.

shedman
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Re: DS4 2.0 blue hdi faulty deNOx system

Post by shedman »

Wheeler, Yes i will see how it goes it is just nice to get rid of the countdown timer. Strange thing is the system showed working again when the fault codes were deleted without doing anything else but hey ho it is french.
best regards, Shedman.