Dreaded P20E8 Adblue fault - advice?

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danlat1415
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Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

I've had my 2017 C4 Picasso for just over 12 months now and the first time ever got a low Adblue level was a couple of weeks ago - so put 10 litres in (didn't fill - think tank takes around 17 litres?)
I also put some Wynn's crystal clean and protect in the Adblue tank.

I also changed the filler cap from the current black top one that was on my car to the replacement white cap one the was recommended by people. (Bought off eBay) Part - 1631999980

Now I get an intermittent Adblue emissions fault which comes on sometimes whilst driving, the usually goes on next restart.
Today I got an 'engine fault - repair needed'.

I ran diagbox and got error code E20E08 - pressure too low (see attached for full error details).

I'm hoping it's not a leak and full new tank needed.
When I take the cap off and look down the hole it looks a bit bubbly, is that normal? Not dishwasher soap bubbly, but like I've only just topped it up.

As a precaution, I've put my older black topped filler cap back on - just in case the white top one I had got was causing the issue. (The eBay item said it was brand new genuine part - but came in an opened Citroen parts bag - so I've no idea if it's genuine, new etc).

Do I need to fully top up the Adblue tank? (Fill until it splashes as though it's full) Or is just adding 10 litres on a 'less than 1500km warning' enough?
Is it safe to add a second bottle of Wynn's to the tank in case any crystallisation clogging anything?

The car was perfectly fine until I topped it up with 10 litres.

Does anything stand out that could help me mitigate things?


Thanks

VIN is VF7**************[VIN obfuscated, can be read by forum staff]
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GiveMeABreak
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Re: Dreaded P20E8 Adblue fault - advice?

Post by GiveMeABreak »

That is the correct part number for the replacement cap:
adblue cap.png
Next the anti-crystallisation - I hope you didn't put a complete bottle in? You're only supposed to dose at according to the quantity of Adblue you have added. Don't put any more in or this can upset the mixture.

10 litres top up is fine - but make sure you follow the manual for procedure regarding opening of doors or switching ignition on when you have topped this up from the warning. It is quite clear about the timings you must leave it before switching the ignition on.

The fault refers to crystallisation between the Adblue injector and the heated urea pipe that goes back to the tank.

It's possible that if you haven't added any anti-crystallisation before now that the damage has been done previously. The anti-crystallisation additive may help prevent further issues and may start to help remove existing crystals, but that all depends on how bad it is. It will take some time to work as it has to work its way round the system and that will be hampered if there is already a blockage.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

Thanks for your response.

I used almost a full bottle, accounting for it being suitable for upto 15 litres, and I added 10 litres to the appropriate 2.5 litres already in (1500 mile warning, based on 600miles/litre estimate).
I followed the manual procedure and the low Adblue warning went away when turned on and was fine for a couple of weeks.

I'd never touched the Adblue until it asked me to top up, and I don't know the history of the car, which I assume was never cared for - given that it has the black cap filler lid.


You say that;
"The fault refers to crystallisation between the Adblue injector and the heated urea pipe that goes back to the tank."

Is this likely to resolve itself with the Wynn's working through? Or is that wishful thinking?
Is it going to be a whole new tank replacement, or a smaller part (cheaper) fix?

This has come at a very bad time, and I'm trying to minimise everything.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by RichardW »

There's no fault for crystallisation, the fault is pressure too low. Could be the pump, the pressure sensor, or injector failed ( but that usually has its own fault. There was a thread recently where someone repaired the pressure sensor - which otherwise only comes as part of the (expensive) tank. You need to clear the fault, reset the denox system, then watch the live data with the engine running to see what it does. Once it starts to warm up status should go from waiting to pressurising and the pressure should rise to about 6 bar, then it should start injecting and the pressure will drop back to about 5.5.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

Thank you
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Re: Dreaded P20E8 Adblue fault - advice?

Post by GiveMeABreak »

P20E8 00 has a specific Technical Service Bulleting and it relates to what I said above for vehicles with this engine (DV6*) which includes your build date. From later build dates they modified the assembly, but in this case check to make sure that the heated urea pipe is firmly in place and has not come apart at any point - which would cause a pressure fault.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

Thank you.
Where is the heat pipe located?
Near the Adblue tank or further away?
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Re: Dreaded P20E8 Adblue fault - advice?

Post by wheeler »

It runs from the adblue tank up to the injector in the exhaust.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

I've cleared the fault and reinitialised the denox system (tank, not catalyst) in diagbox repair pack area and that has cleared the engine warning light now.
I'll have a physical look at the pipe and monitor the live feed to see if the pressure increases.
I know 4 is the lowest it reads and needs to go to around 6 then pump kicks in and drops
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

The low pressure fault is back.
The live data shows it doesn't go above 4, so doesn't kick in the pump.

So seems like a new tank needed 😥

Is it possible to replace the tank myself, or is it a garage only job?
I would have assumed just disconnect all hoses and electrical connectors, unbolt and lower the tank.
The fit new on in reverse, and reinitialise denox system (tank) in diagbox?

Looking to save costs where I can, so buy part and fit myself if possible.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

Thanks for all your help.
Tank ordered and read the technical instructions and had a good look at the car, and seems a very straightforward procedure of swapping out the tanks.
Annoying that I've waisted adblue filling up the old one, so will now drain and be wasted (disposed correctly) - as I want to make sure the new tank is nice and fresh.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by GiveMeABreak »

Best of luck and you may want to consider using some Wynne's Anti Adblue Crystallisation when it's full and back working again.
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Re: Dreaded P20E8 Adblue fault - advice?

Post by danlat1415 »

Thanks. Already bought some ready 😊 along with a tank's worth of Carlube adblue.

My old tank still had the old black cap, so I think when the low light came on and I filled the tank and replaced the cap, the old black cap had caused a pressure seal in the tank, so it only went down hill from the moment I opened it.