Adblue tank repair details

[Stuart W]

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.

[CitroJim]

That's fantastic Stuart and huge thanks for posting this, most valuable in the extreme

[shtu]

That is some impressive work.

Might be worth pointing to a couple of suitable pressure sensors?

[Harrythephot]

Fantastic job.
I wonder how many tens or hundreds of thousands have been wasted on new tank fitment, when a simple repair may have worked.
Well done.

[Stuart W]

The pressure sensor that I used was a 0 to10 Bar 3 wire sensor which is available on Amazon or ebay.I will post the part numbers of the unit I used.Incidentally , when I tested the actual fluid pressure with the new sensor , it was 6 Bar which is spot on.

[wheeler]

Excellent job

[Stuart W]

PARTS LIST
Parts list for adblue tank repair.All are Amazon part reference numbers (ASIN)
I have not included the jubilee hose clips which are readily available elsewhere.

Pressure sensor 10 bar 3 wire type B08DKFKLWK.

G3/8 Thread adaptor for sensor B09BQF8HC8

Autohaux fuel line connector pack 6.3mm B0BSDB8YC4

Brass 8mm Tee piece B07MX7DZ4X

8mm fuel hose B0C5CPT9QQ
These parts are all from Amazon.and total about £ 30.No doubt some may be available for even less online but I was keen to get the car fixed asap.