C4 Emissions Fault Starting Suspended

cthompson · Unread post by **cthompson** » 01 Jul 2023, 13:51

Good Afternoon Everyone,

A work colleague of my wife asked me to look at her 2016 citroen c4 as it won't start.

They were getting a top up the adblue message saying it would stop starting in so many miles, there is plenty on adblue in the tank.

They kept running the car then at 50 miles it suddenly came up saying it would no longer start at the next restart.

With the ignition on the urea light and battery light are both flashing, and the centre screen showings emission fault starting suspended or something similar.

Unfortunately my copy of diagbox decided to play up yesterday so I had to use my autel scanner instead, this shows a fault code of u029e which it shows is no communication with the nox sensor. This fault wouldn't clear with my scanner.

I had a look under the car, assuming the nox is the last sensor in the exhaust after the centre box the wiring didn't look obviously damaged.

I removed the undertray in front of the passenger rear wheel as I wanted to find the eolys tank and check if it had any fluid, I found the tank shown in the pictures which sounds distinctly empty when shaking it (apologies about the picture quality, the car can't be hacked up where it currently is.)

Based on the above I've a couple of questions, firstly would the u029e code stop the car starting (I don't want to go through manually tracing all the wiring for it to find it's
a red herring.)

Secondly if the tank I found is the eolys tank and is as I suspect empty would that also be able to stop the car starting? Would an empty eolys tank present different fault codes?

When I get chance I'll need to go through the rigmarole of reloading diagbox on my laptop as I'd imagine a proper citroen fault code should provide more direction.

Thanks for any help,
Chris.

Unread post by **RichardW** » 01 Jul 2023, 14:31

Welcome along Chris!

These can be a mare... Eolys and Adblue are separate, and only adblue level or faults will prevent starting. If you re-set the Denox system then you should be able to get it started which will allow you to then see what is going on with the de-nox system. However, if there was a message that level was low when there was plenty in the tank, then it's likely that it needs a new tank assembly - but the message can be a bit confusing sometimes!

cthompson · Unread post by **cthompson** » 01 Jul 2023, 16:35

Thanks Richard, think my first step is going to be to reload my laptop then and test it on another mates peugeot before rescanning the citroen in question

cthompson · Unread post by **cthompson** » 11 Jul 2023, 13:11

So I finally managed to get diagbox working on my laptop again.

Managed to reset all the denox stuff and get the car starting again.

As soon as you start it it reports an engine fault which shows as u029e 87 as shown in the screenshot.

The cars going to be left with me at the weekend when I intend to remove the adblue tank and eyeball it all for anything obvious.

I've a feeling the most cost effective solution to this will be having the adblue stuff coded out but we'll see what I find.

Thanks
Chris.

Unread post by **PaulC5** » 11 Jul 2023, 13:48

If you remove/code out the adblue system you might find the car will not pass the MOT so the car owner will not be pleased. It may turn out a new adblue tank/pump is needed, there are many posts over the internet where new tanks are needed at a cost around £1000 so not cheap.

Unread post by **RichardW** » 11 Jul 2023, 14:47

I imagine you will find the adblue has leaked into the electronics side of the tank and ruined the ECU. New tank required!

We can't condone tampering / deleting emissions control equipment, so please don't discuss it here!

cthompson · Unread post by **cthompson** » 11 Jul 2023, 15:44

Hi Richard understood re. bypassing the system.

Can anyone confirm if the adblue tank is the one in the original pictures in front of the passenger rear wheel or is it somewhere else?

Thanks
Chris

Unread post by **RichardW** » 11 Jul 2023, 16:42

No, that's the Eolys tank, the adblue tank is on the other side (and considerably bigger!)

cthompson · Unread post by **cthompson** » 15 Jul 2023, 13:43

So looked at this earlier today, adblue tank is directly under the boot floor, 3 nuts holding it in, a couple of wiring plugs and a clip for the adblue feed to the injector.

Removed the tray containing the ecu and pump, as suggested there was adblue in there so the tank is leaking. Small amount of corrosion on a couple of the micro processor pins on the ecu pcb, no other major damage or signs of corrosion.

Couple of the wiring connector pins were a bit green, I've sprayed the ecu and wiring connectors with moisture repellent and scrubbed the corrosion off with a cotton bud.

Blew the whole lot off with compressed air till nicely dry.

Confirmed the pump and solenoid work with a 12v tester and checked all wiring continuity with a meter.

I've not bothered checking heater resistances yet as I don't think a fault with them would cause a communication error but it's something I can look at later.

Shortly I'm going to reconnect the ecu part of the tank and see if I can get the fault to clear now it's all dried out, if it doesn't communicate then I'll check I'm getting 12v from the car at ignition on and possibly look at reflowing the solder joints on the pcb.

I found the below website when looking into this which gives a good overview of the system.

https://www.elektroda.com/rtvforum/topic3827598.html

Thanks
Chris

cthompson · Unread post by **cthompson** » 16 Jul 2023, 10:50

And a bit more done with this, manually drying it out didn't clear the fault code so after reading about someone who's had success with using an oven to dry out the ecu and reflow the solder I thought I'd give it a go, the ecu wasn't working anyway so I saw little to lose.

3 minutes at 180 degrees in a fan oven propped up on an old socket and the car now reports no communication error or any other fault codes $\:D/$

The next task is to see if I can work out where the leak into the ecu area is coming from, either the short pipe that connects onto the pump is leaking (are new o rings or even the pipe available?)

If it's not that pipe then either part of the pump setup could be leaking or there's a crack in the tank housing.

I'm going to try propping the ecu housing up and run the priming setup on diagbox and see if it gives me a clue.

Thanks
Chris

GiveMeABreak · Unread post by **GiveMeABreak** » 16 Jul 2023, 11:00

There are no spares for the internals on these tanks - only new complete tanks are supplied Chris, along with supply pipe and harness, caps etc. 10/10 for effort though. I've had very limited success with graphics GPUs via the way of the oven - lasted temporarily before a replacement was needed, so fingers crossed the ECU 'repair' will last longer in your case.

The additional issue in your case is the whole thing is going to be subject to a lot more stress in the vehicle with all the shock and vibrations.

Tom309 · Unread post by **Tom309** » 16 Jul 2023, 15:49

Hi Chris, well done on the investigation and getting the comms to work!
I would suggest that you look for the leak from the pump onwards as this is pressurised to 6 bar when the system works. In my case the leak was in the expansion tank (the membrane had a split), but there are o-rings around the non-return valve (solenoid), pump and pressure sensor.
In the attached files, the expansion tank is shown by blue arrows and the membrane position by red.

cthompson · Unread post by **cthompson** » 16 Jul 2023, 18:02

Testing using diagbox didn't show up any sign of a leak so I've returned the car to it's owner and we've agreed that if no faults come up in the next couple of weeks I'll remove the tank and see if there's anymore sign of adblue in there