Error code P0234 = boost pressure exceeded

[cit-rotti]

Error code P0234 = boost pressure exceeded.
Temporary fault - occurred 2 times in quick succession in trailer mode about 1900 kg at approx. 171000 km.
Vehicle: C5 R/2007/2,2 HDI/175PS/ VF7**************[VIN obfuscated, can be read by forum staff]
Now to my problem. I know that this error can have dozens of causes, but maybe with the error code and the following description a narrowing down is possible.
The vehicle goes into emergency mode and can therefore hardly be driven in trailer mode.
Of course, a diagnostic device to clear the fault was not included.
After stopping, disconnecting/connecting the battery (negative terminal) and the obligatory minutes of silence, the box worked again.
Questions:
The model has 4 solenoid valves and lots of vacuum hoses for the turbo control - is there any sign of damage in the turbo control or was it just a coincidence?
Or even a turbo damage with a jammed adjustment or or...?
Thank you for any information and help.
Greetings Wolfgang

[GiveMeABreak]

Hi Wolfgang

If this fault is present, then official guidance is to replace the turbocharger pressure regulation electrovalve (1).

I believe that is part: 1618X2.

[cit-rotti]

thanks for the quick information

Greeting Wolgang

[xantia_v6]

Also check that the filter on the atmospheric port of the valve is not blocked or obstructed.

[Dommo]

Hi all. Apologies to tag on to an old topic, but I have this same issue with my C5 mk1 facelift 2007 with the same 173 DW12BTED4 engine.

I changed the pressure regulation electrovalve as per the above message from givemeabreak and the engine drove differently, in a good way. However twice since then I have still had the same error occur. And I’ve had the issue several times before replacing the electrovalve, so it seems to be an ongoing issue.

The occasions it seems to happen for me is mainly when accelerating up a gradient on a motorway with cruise set to 70, or a gradual acceleration up to 70. Flat out it’s totally fine and behaves, but it’s as though that accelerating gradually in one gear for too long is what upsets it.

Looking into it previously (I’m sure there’s another thread on here about it, but it might be another ecu type) I saw that the error occurs when boost pressure creeps up above the requested boost, is this the case? If so then the error occurring with gradual acceleration up to speed, or keeping to 70mph using cruise control up a gradient, as opposed to when flat out, would make some sense.

Any other suggestions here? Could the turbo wastegate(s) be problematic? Could it be the vacuum lines to the turbos from the electrovalve? It’s at 181k miles, and it happens so infrequently that I don’t think I’d go down the turbo replacement route for this error. But limp mode on the motorway is a bit of a nuisance!

Cit-Rotti, did you ever get to the bottom of your fault ?

Thanks all. Dom.

Edit - for the record my ECU is the Bosch EDC16 system

[xantia_v6]

It is possible that something is preventing the wastegate from opening quickly when the ECU commands it. I would be checking for tightness in the actuator linkage, or a restriction in a vacuum hose. Also check that the little filter on the atmospheric port of the control solenoid is not blocked.

[RichardW]

I'd have thought it's likely to be variable geometry - and likely it is sticking when wide open. What does the live data say about the requested and reported position?

[Dommo]

Thank you for the reply both.

Regarding your suggestions, I’m unsure if it’s a variable geometry system as it’s a twin turbo setup on the 173 2.2’s, I feel variable vanes would add more to the complexity but it could well be for all I know. I also suspect this setup will make checking actuator arms difficult, but I’m willing to have a go!

I shall try and check the vacuum hoses / system with a vacuum pump at some point. It seems to take a good while of a low but constant load before it throws the fault up, and even then it takes a long time to crop up. So
I aren’t sure I can easily attempt to replicate it.

The filter on the atmospheric port seems clear, I could blow through it easily enough.

And lastly I’ll try to get some live data, but unfortunately as said it takes so long to cause the fault that I will struggle to catch the fault red handed as it were.

Thank you both for the suggestions. It’ll take a while to get back to you with my results so please don’t expect a quick reply unless there is something really obvious I missed once I get to it.

Dom.

For the record this is the Lexia screenshot of the fault (see attachment)