Adblue tank repair details

[01484]

Some of you may have seen my posts on here when my 2015 Grand picasso suffered the all too common adblue pump failure with persistently screaming pump and Service light on, engine fault light and urea light on.
Diagbox says leak/ low urea pressure.
It is worth noting that diagbox says pressure is 4 bar even when its actually zero.It does not read below 4 bar.
However, when I removed the tank and ran the pump directly from 12 volts with a pressure guage attached to its output, the pressure shot up immediately way past the required 6Bar, reaching 8 or 9 bar in seconds.So the pump was not faulty.
The culprit was the pressure sensor that is built into the pump body.I metered the output from this sensor and it did not register the pressure changes at all.This explains why The pump was screaming, trying to reach a pressure that was not being seen by the sensor although in fact it was already too high.
The faulty sensor also mislead diagbox and me for a while, by saying the pressure was too low.The system will not inject the adblue if it thinks the pressure is too low.
This noisy overworking adblue pump seems to be a commonly reported problem so I suspect that the majority of adblue tank failures are due to this sensor.
THE FIX.
Since the original sensor is a purpose built part moulded in plastic and attached to the pump motor it cannot be replaced without PSA manufacturing a spare part.
The answer is to fit an external sensor in the urea output pipe that runs to the injector.
I bought some 6mm fuel line connectors, male and female ant with some 8mm hose and 8mm brass tee piece inserted this short extension pipe from the output of the blue tank.The Tee piece connects to an 8mm to femake G3/8 thread adaptor to accept a standard 3 wire pressure sensor (10 Bar)
The existing Citroen pressure sensor has a small 3 pin plug with red,black and yellow wires.Unplug this from the sensor and connect the new sensor to the same wires.In my case the new sensor had a green wire instead of yellow, but connect this green wire to the yellow of the Citroen lead. The Red wire is + volts supply and the black wire us - volts supply.The yellow or green is the sensor output which should move from 0 volts up to 5 volts as the pressure increases.
Since the sensor comes with about 30 cm of wire attached you will need to drill a small hole in the plastic lid which covers the pump and its electronics.
Feed the sensor wire through this and connect the red, black, green wires to the old sensor lead.Seal the cable hole to prevent dirt and moisture getting to the electrics.
While the tank is out, it is worth offering up the Tee piece extension hose to find a suitable location for the sensor to fit as space is limited between the adblue tank and the spare wheel.Adjust the hose length to allow the sensor to fit into one of the recesses in the tank moulding.
For belt and braces, I put two jubilee clips, close together, on each pipe joint. So 12 hose clips in all.
It may be necessary to bleed the adblue system with diagbox before clearing all error codes.In the course of doing this mod I have only had to bleed the system once.Previous times it was ok.
To see what is happening with your faulty tank it is worth checking the pressure by using a piece of this same 8mm pipe and clip on 6mm fuel line connector running to a 0 to 10 bar pressure gauge, also available from ebay or Amazon.Once the engine is warm the adblue pump should operate periodically to bring the stored pressure up to 6 Bar.
If your adblue pump is screaming and the fault codes are saying low pressure then it is worth doing this low cost fix.
All parts were bought from Amazon for a few pounds.See my attached photos.

Would have been good if you provided a video or multiple picture of the final product how its all connected up. I can kind of understand the tutorial but positioning the sensor and the layout would have been good to see it all.

[MattBLancs]

Hi guys i am new to this forum.

On the diagnostic it's 4 bar and doesn't move. I am suspecting the pressure sensor. How can I test the pump? By attaching 12v car battery to it? I can do the mods to the tank that are shown at the start of the forum but I'm struggling to understand and follow it. If I buy a pressure sensor and fit that and delete the fault codes will that fix it? Or do I need to modify and add pipes etc to fix it? Thanks for your help and time any help is very much appreciated, been stressing from this fault for 2 days now . Was going to order a 2nd hand tank tomorrow but think I can save that money and try this.

I've not yet had the joy of this fault but have read this informative thread with interest. Some quick answers based on my understanding, others will likely be able to correct:

4 bar I believe is a "minimum value" rather than true reading (imagine it can tell you say 4-8 bar but not 0-4. Anything less than 4 is just shown as 4.

Could be dead sensor (reading nothing but ECU is displaying it as 4, as above) but I believe it also could be dead pump (sensor is, correctly, reading 0 as pump not doing anything, but ECU is displaying minimum value = 4.

My understanding is if sensor playing up, pump can be made to run continuously / too much and this can kill the pump off.

Not sure in testing the pump, sorry.

[MattBLancs]

Would have been good if you provided a video or multiple picture of the final product how its all connected up. I can kind of understand the tutorial but positioning the sensor and the layout would have been good to see it all.

Keep digging on this thread, I'm sure there's a picture of it assembled on here somewhere. If I find it I'll quote / link it for ease of reference

[01484]

Thanks Matt for your reply. I looked throughout each page but cant seem to find a picture. There's a couple of pictures on the first page but thats about it. I have all the parts added to my amazon basket just thought find out first what to do before I take tank off and start messing around with it.

[perfidus]

Hi
The solution of Stuart W is ok but more invasive/laborious, try to follow this more recent post viewtopic.php?p=838630#p838630
The original pressure sensor can be bought from Amazon as a sample.
But be careful, in this type of tank failure if the pump was running execessively waiting for pressure to be measured OK, it could affect the O-rings of the pump and the ad-blue solution starts to drip from the pump body into the electric motor and then onto the circuit board. This can cause a total electrical failure of the unit.

[01484]

If I had known I would have bought just the pressure sensor from amazon alone. Upon looking seems like you have to wait slightly over a week for it.
Bought the Stewart kit this morning its arriving tomorrow will see how it goes.

[MattBLancs]

Image of aftermarket (different shape, mounted externally) sensor and t-piece assembly (in neat plastic box) here:

viewtopic.php?p=814327#p814327
Description here:
viewtopic.php?p=824111#p824111



Alternative fix, replacement of original sensor:
Image of aftermarket same type, same shape sensor here:
viewtopic.php?p=816702#p816702

Identification of sensor location in the original adblue system housing here:
viewtopic.php?p=818580#p818580

Pentalobe screws holding it in
viewtopic.php?p=823068#p823068

(Still looking, will edit if find more of use )

[01484]

Hi Matt thanks a lot for your help. Very much appreciated. My parts are due to be delivered this afternoon, hopefully start the process today and see what happens.

[01484]

Not having much luck with mine so far. Tried the Stewart method and I cant say for certain if it worked 100% or not but the joint where the hose connected to the tank the clips you buy seperate kept leaking. Car seems to be fine. I didnt drive it long enough as the ad blue was leaking so got worried it would crystallise in the pipes. So I bought the actual sensor from Alibaba the 4 to 7 bar one fitted it today and getting the urea fault again now but can also hear the ad blue motor whirring this time too. Never heard the motor before.
Not sure if it could be a faulty sensor they sent. I think might as well revert back to stewarts method and try stop the leak somehow. Starting to be a nightmare now.

[Trickiedickie]

On a working system the adblue motor usually kicks in after starting the engine and then driving a mile or 2. You get to hear it, a whirring sound that lasts only a second or so from behind you.

I am not 100% sure but something to bare in mind is your ecu system might have recorded a permanent fault code in which case it might have to be cleared with a diagnostics tool (Diagbox) by reinitialising the adblue unit.

[01484]

Thanks I was waiting for one of the experts to comments. When I took out the old pressure sensor yesterday I didnt realise the old washer from the sensor was still inside. I put the new one in and closed everything back. Today I opened it again removed the older washer and left the new one in.
I cleared all the faults using the diagun x431 app. Reset the ad blue, reinsitialised sensor and urea pump etc.
I started the car and after around 10 mins or so gently revved it till engine temperature got to 90 degrees. I lrft it running for around half an hour. The pump activated once for few seconds and then stopped. I wasnt sure if its fixed the fault or not. I drove around 2 miles and got to my destination and then before I was about to turn car off I could hear pump turning on for around 5 seconds then turning back off. Then it turned back on maybe after 30 seconds later then turned back off after 5 seconds. In the app I could see it saying something like pressure stage 2 or something for the ad blue system and then pump activating and stopping. I turned the car off worried the pump might fail as it did it a couple of more times. I haven't got an error so far. Im not entirely sure if its fixed yet or not. Maybe the sensor has actually sealed properly after removing the second rubber washer?? Im just worried that like someone said the pump can wear out if its running often. Would you say this is often? Iv not heard it running before maybe iv not thought about it. What i also noticed was the pressure remained at 4 bar all the time even when the pump was working. Is this because its a third party sensor from China and not actual manufacture one? I think Stewart said not to look at pressure sensor as it won't be accurate but that was for his external one this one from China is internal so would same principles apply?
I was thinking of opening it again tomorrow and fitting the 10 bar sensor the one Stewart mentioned or shall I wait and see if error comes up again and then revert back? What would you advise?
Been so stressed about it not been driving it much now so it doesnt worsen. Been relying on family to do shopping etc.
Was thinking if it doesnt fix paying someone to remove ad blue system and remapping it, take the headache of the ad blue system out completely.
Thanks a lot for your reply
Sorry for asking so many questions

[Trickiedickie]

What i also noticed was the pressure remained at 4 bar all the time even when the pump was working.

The pressure should be anywhere between 5 to 6.5 bar approx if it is working correctly. It's mad but on these PSA cars 4 bar really means 0 bar!!!
Maybe the app is not doing it's job properly as you said no more errors for the moment which is of course a good sign so keep testing.

[01484]

Yes will keep testing. Need to go on a longer journey. At moment will leave as it is. If error does come up with change to external sensor. Hopefully it doesn't show up. Will keep you updated.
Thanks

[01484]

Just been out, drove around 2.5 miles again... stopped at destination and then could hear pump turning on (whirring) for few seconds then off again. It kept doing this maybe 6 or 7 times and then stopped. I kept the car started wanted to make sure the error doesnt show up again. Then the bloody crap engine fault sign popped up on dash again... after I started driving again the emissions fault came on along with service and the urea light.
Im suspecting the new pressure sensor maybe faulty... Will try the external pressure sensor tomorrow and see if that has any difference.
Will update tomorrow.

[perfidus]

If the error you read with x431 app is the same low pressure error, maybe you should measure the real pressure with a manometer to see that you have a good sensor. The fact that you hear the pump means that it have authorisation by temperature (no NTC failure) and the problem is still the pressure. You can also try to test the sensor with a calibrated pressure gauge and a 5V power source.
quote from Stuart W: "The Red wire is + volts supply and the black wire us - volts supply.The yellow or green is the sensor output which should move from 0 volts up to 5 volts as the pressure increases".