P0401 fault code.

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Bionicman
Hyper Poster
Posts: 560
Joined: Tue Aug 15, 2017 5:13 pm
Engine size/power: 2.0 TDI (140bhp)
Location: Beverley

P0401 fault code.

Post by Bionicman » Mon May 18, 2020 4:30 pm

Hi guys, just went back to work today and the engine management light came on, read code and it came up P0401 which relates to the egr valve having a insufficient flow. Caddy has been parked up for 8 weeks and it has just been started once a week for 10 mins. Do not know if this has any relevance on it happening just going out today with it being stood still for 2 months or what. Anybody shed any light on this? By the way a new egr valve was only fitted by VW less then 2 years ago so surely it is unlikely to have gone faulty in such a short period of time , but then again nothing surprises me after the emissions fix.

SnoWhite
200BHP+
Posts: 287
Joined: Sat Aug 15, 2015 6:41 pm
Engine size/power: 2.0 CR TDI (108bhp)

Re: P0401 fault code.

Post by SnoWhite » Mon May 18, 2020 5:26 pm

Even if you have battery worries it is probably a bad idea to simply start your caddy and leave it at idle for 10 minutes before shutting it off. Indeed if you have a healthy battery it should start up fine even after many weeks parked doing nothing (provided you have not left any lights on).

Each time you start the engine from cold but don't drive anywhere you are giving the emission handling kit a real hard time, as the catalyst and DPF can quickly clog up with soot if they do not get super hot from time to time to clear out the system. These engines need to be driven not left at idle.

For now I would stop doing those cold starts and only start the car when you actually intend going out for a decent motorway run ideally 10+ miles at 60mph+ in top gear out/back should be enough to get the enginefully up to normal temperature to allow the emission handling kit up to complete a regen and basically clean itself.

If you are lucky just taking the Caddy out for a quick motorway blast once you are allowed will sort things out, but if you keep shutting the engine off part way through a re-gen then eventually the software concludes the DPF soot load is too high and throws a warning which at least officially requires a visit to a dealer to carry out a forced regen. If you have VCDS you can follow the "forced regen" instructions on Ross Tech.

You mention the emissions fix - does that imply you have had it done? If your Caddy is within the 2 year free warranty period then call a dealer and get them to fix it for free. If they are happy to fix it for free great - however as soon as it is working fine - I would track down a decent remap as when properly tuned these vans will use less fuel with better performance than vans still running with that daft emmission fix.

Personally I would never let VW do that emission fix you will find plenty of sorry tales on here. If they simply deleted the offending testing cheat code - fine, but they basically altered the emission handling so it now runs flat out virtually all the time - guzzling fuel - and as a result is probably putting out more emissions than an unmodified Caddy. The need for extra fuel means the injectors work harder and fail often, and all those emmissions have to go somewhere - that is why vehicles with the emmision fix seem to be suffering with far more clogged EGRs, more clogged DPFs and more wrecked catalysts. None of which are cheap or easy to replace.

Bionicman
Hyper Poster
Posts: 560
Joined: Tue Aug 15, 2017 5:13 pm
Engine size/power: 2.0 TDI (140bhp)
Location: Beverley

Re: P0401 fault code.

Post by Bionicman » Mon May 18, 2020 6:21 pm

@snowhite, will take that advice onboard and not start it unless going for a run out, the emissions fix has been done on my Caddy years ago and has since had a new egr valve fitted in last 2 years so I don`t see why it should have gone faulty in such a short period of time. Maybe somethings just stuck with it been stood idle for 2 months and a blast down the motorway may cure it. What is the cause of the insufficient flow fault code?

SnoWhite
200BHP+
Posts: 287
Joined: Sat Aug 15, 2015 6:41 pm
Engine size/power: 2.0 CR TDI (108bhp)

Re: P0401 fault code.

Post by SnoWhite » Tue May 19, 2020 7:51 pm

What is normal use for your Caddy?

The tdi models are brilliant if they are mostly used long enough to get fully up to temperature and ideally with a regular motorway blast. The tdi's do not like masses of short, and stop start trips as that can quickly clog up elements of the emissions handling kit.

The fault code implies an EGR low flow alert - which certainly could be down to a stuck EGR, but can be down to othe rthings. It can even happen to a quite new EGR, if you do loads of short trips with the van rarely getting up to temperature before you shut it down as that means you are never giving the van a decent blast to regen and clear out the emissions handling kit. If it is a struck EGR there are firms like TerraClean who may be able to partially clean the EGR system but if it will not be a long lasting fix if your use never gets the van up to temperature.

In the VW brochure small print they recommend people buy a petrol model rather than a diesel if it is mostly going to be used for short trips.

You know my views on that emission fix, which may well be a factor in the current EGR fault. Hence once you get the chance you may want to get your van a professional rolling road remap, but avoid man with a laptop solutions which may be cheaper but can equally create new problems. If you mention this forum, people like Pendle Perfermonance offer forum members a discount and will give your Caddy a real wake-up call.

Take care.

SnoWhite

Bionicman
Hyper Poster
Posts: 560
Joined: Tue Aug 15, 2017 5:13 pm
Engine size/power: 2.0 TDI (140bhp)
Location: Beverley

Re: P0401 fault code.

Post by Bionicman » Mon Jun 01, 2020 4:33 pm

Latest on this fault code. Had van in at VW van centre today and they could not find anything wrong with it. They sent me a video of the egr pipes that they took off and although they appear to be slightly sooted up there is no blockage in the system. I spoke to the technician on the phone and he said the egr valve and pipes are perfectly clean and the valve is operating correctly. Just think that this is not a good enough diagnosis as surely something is causing this fault code to come up. I personally think the egr valve is stuck in the closed position which short term may not be a bad thing but long term I am sure it will cause issues with the dpf. Any way he said if it happens again they will have it back in on the diagnostics and see what is going on.
And finally its a bit different in the VW showroom now as you have to sit 2 metres away from the booking in desk which is sited behind a 10mm or so perspex screen with an opening at the bottom to hand over your key which they sanitize straight away after putting on the latex gloves of course, you can`t even get a free coffee which I must say it is good coffee. Hey ho lets hope things will go back to normal as I can`t see this is going to be good for people wishing to buy a new vehicle.

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