A few days ago I got the dreaded P20E8 error "Urea pressure too low".
Now in most cases the recommended solution is an expensive one; replace the whole tank. I took it personally though and decided to fix it.
For this, I found a great guide here https://www.elektroda.com/rtvforum/topic3827598-180.html . Apologies for posting a link to another website, but this is too useful not to be shared.
Removing the tank is a walk in the park. Its held on by 3 bolts/washers, you don't even have to raise the car. There are 2 connections to it, the tube feeding pressurized urea to the injector and the power+CAN comms cable.
You can easily drain the tank by a side mounted drain valve. It has a torx screw that you remove first, then twist and remove the plug to drain.
After dropping the tank, you have a few screws to remove to access the internals of the pump assembly.
In my case I had a faulty thermistor on the heating plate (its been mentioned a few times in the above website) and two of the heater cores had loose connections. I ended up bypassing the heating plate thermistor by inserting an NTC 10k thermistor into the hole that goes to the plate. To fix the loose connections, I had to dig out the heating elements and resolder new wires. I have also checked the pump, solenoid and pressure sensor to make sure they work as expected, and they seem to do so.
To be on the safe side, I replace the urea injector.
Bottom line is that this specific error means the urea tank refuses for some reason to work. It could either be that the electronics are flooded and corroded to the point of not working at all, or it could be something as simple as a temperature sensor throwing a fit. At the end of the day however, I don't like spending £1000s to fix something that should be fixed with a few pounds. I realize this is not a fix for everyone, but for those not afraid to use a wrench and a soldering iron, give it a go.
I have yet to test if my repairs have been successful but will let you know tomorrow as soon as I do a few miles to allow for the system to kick in.
Also, make sure to have a read on this extensive thread on the issue
www.cactusforums.co.uk
Now in most cases the recommended solution is an expensive one; replace the whole tank. I took it personally though and decided to fix it.
For this, I found a great guide here https://www.elektroda.com/rtvforum/topic3827598-180.html . Apologies for posting a link to another website, but this is too useful not to be shared.
Removing the tank is a walk in the park. Its held on by 3 bolts/washers, you don't even have to raise the car. There are 2 connections to it, the tube feeding pressurized urea to the injector and the power+CAN comms cable.
You can easily drain the tank by a side mounted drain valve. It has a torx screw that you remove first, then twist and remove the plug to drain.
After dropping the tank, you have a few screws to remove to access the internals of the pump assembly.
In my case I had a faulty thermistor on the heating plate (its been mentioned a few times in the above website) and two of the heater cores had loose connections. I ended up bypassing the heating plate thermistor by inserting an NTC 10k thermistor into the hole that goes to the plate. To fix the loose connections, I had to dig out the heating elements and resolder new wires. I have also checked the pump, solenoid and pressure sensor to make sure they work as expected, and they seem to do so.
To be on the safe side, I replace the urea injector.
Bottom line is that this specific error means the urea tank refuses for some reason to work. It could either be that the electronics are flooded and corroded to the point of not working at all, or it could be something as simple as a temperature sensor throwing a fit. At the end of the day however, I don't like spending £1000s to fix something that should be fixed with a few pounds. I realize this is not a fix for everyone, but for those not afraid to use a wrench and a soldering iron, give it a go.
I have yet to test if my repairs have been successful but will let you know tomorrow as soon as I do a few miles to allow for the system to kick in.
Also, make sure to have a read on this extensive thread on the issue
AdBlue Tank Replacement / UREA warnings / Emissions...
TL: DR Summary: if you've stumbled across this chances are you've got the UREA warning, fault messages and a countdown to the car not starting, chances are you need a new UREA tank, it's very expensive but contacting Citroen directly (0800 0939393) might result in it being replaced with a new...
www.cactusforums.co.uk
