limp mode problem

[alltmor]

Hi, have problem with my vw golf 2ltr tdi mk5 golf BKD engine.
started going into limp mode while overtaking, have read codes on my hand held scanner and come up with,
P0401- exhaust gas recirculation flow insufficient.
P0234 - turbocharger overboost condition.
can anyone help me sort this problem??

[Rob69]

It needs a full scan and more diagnostics, could be the turbo vnt sticking. Try Kennys vw & audi specialists in Inverness.

[Thimoteus]

Try changing the engine oil to a top grade oil. this did happen to me on an A6 2.7 with the overboost message, turned out I had the wrong grade oil in the engine. Always use Shell Helix professional or Castrol nowadays

[Crasher]

You could have a vacuum control system problem there caused by a split hose or valve leaking or a faulty EGR valve and a dirty turbo, P codes alone can't tell you the full story, the outputs and measured blocks for the components need to be checked. You could go and fit a new EGR valve and turbo only to find out it is a simply vacuum leak.

[alltmor]

thanks for info Rob will check them out

[alltmor]

Hi Crasher, thanks for your comments.
Have had the over boost code coming up since had car (8years), just turn ignition off then on again and goes no problem.
Went to garage today and they think might be EGR Valve dirty or sticking, recommend new one??
Where to look for split hose??

[niall campbell]

I would wait for the fault to develop, slit hoses are cheapest option at the moment

[alltmor]

removed EGR valve at weekend and cleaned it. was able to push piston up and down with no problem.
Took car for a drive and once got over 60mph it went back into limp mode and same faults coming up.
can anyone tell me which hoses to check for slits or cuts ??

[Crasher]

Did you check the EGR valve diaphragm to make sure it was not punctured? To check for a vacuum system leak, firstly apply a vacuum to the source feed pipe of the servo line and see if you can pull a constant stream of air. Alternativlly you can just suck on the small vacuum hose but this will not eliminate the servo and its lines as a source of any vacuum problem. Quite often we find the valve block unit is leaking internally.

[alltmor]

update, fitted new EGR Valve and problem still exists. any advise on which vacuum pipes to check would be appreciated. many thanks

[alltmor]

so been to local garage and have come up with these fault codes.
16618 -
engine boost condition - limit exceeded. Hose connection wiring TC wastage, regulating valve TC wastage.
16785 -
EGR Recirculation flow. - Hose leak/blockage basic setting not carried out. EGR valve/solenoid.
any info on what these mean or advice on how to fix would be most welcome.

[Rob69]

They're basically the same codes you posted in #1 (http://www.vwaudiforum.co.uk/forum/usertag.php?do=list&action=hash&hash=1) , at the end of the day you need to check for vacuum leaks and get better diagnostics done not just generic OBDII codes. N18 solenoid for EGR valve, N75 solenoid for turbo VNT actuator, my money is on split or porous vacuum hose or the VNT guide vanes being sticky but you won't know until you diagnose it, or fix it by chance either changing the turbo or finding a vacuum leak or sticking solenoid. You're already into this for the cost of a probably unnecessary EGR valve.

[Crasher]

You need to check the vacuum control system for leaks but the overboost code is probably not linked as a vacuum system leak normally causes an underboost code.

[alltmor]

ok thanks for your reply will try find leaking hose

[Johnnyb82]

overboost condition is usually related to blocked vgt {variable geometry}

[Crasher]

Really?.....

[A6C5V6TDi]

Usually broken vaccum hose, N75 and sticky vanes. I'v had all three. Crasher, how can the EGR cause overboost?

[alltmor]

thanks for your reply, will try and find broken hose.

[Crasher]

@Crasher (http://www.vwaudiforum.co.uk/forum/member.php?u=6324), how can the EGR cause overboost?

It can't, why? A vacuum leak in the system can cause underboost but not overboost.

[A6C5V6TDi]

It can't, why? A vacuum leak in the system can cause underboost but not overboost.

I thought you said EGR said EGR can cause over/under boost problems. My bad.

[Danielni]

Did you sort this problem, I have the same.