Intermitant Boost Fault (Code 17965)

[dazrick68]

2001 Passat 1.9 tdi with an intermitant boost fault. The car has been driving great for some time. Having an 80,000 mile service including a cam belt change last week the car was better than ever. The car would boost as normal for a 5-10 mile drive then suddenly nothing, no boost. Stop the car, turn off, restart, all normal again for a few miles.
I've checked the hoses around the turbo/intercooler and various vacuum pipes, but nothing amiss.
Yesterday, took the car back to the garage that serviced the car to have the fault codes checked, this is what they reported: CODE 17965 TURBOCHARGER PRESSURE CONTROL LIMIT EXCEEDED INTERMITANT FAULT.

What does this mean? Been told it maybe a holed/split pipe, but i've checked these!
HELP! PLEASE OFFER ME SOME ADVISE.

[BLASTER]

It could be the turbo itself, I had the same sort of problem 18 months ago, turns out the vains in the turbo were carboned up so had to replace the turbo! best of luck I hope you get it sorted as my recon unit cost me over £500

[ini]

If you definitely have no vac control leaks, the overboost could be a bad N75 or a defective vac actuator capsule on the turbo.

If you operate the mechanism by hand you will be able to feel if the spring is working ok, it takes a lot of force just to move it from the vanes 'fully open' position.

The most likely cause is that the VNT mechanism itself is clogged up with exhaust crud. (car mainly used for short journeys)

You can clean the vane & ring mechanism in several ways: chemically, heat, manually work the mechanism or dismantle and clean.

Chemically is probably the best solution.

See this post:

https://www.vwaudiforum.co.uk/forum/s...ad.php?t=31278

[dazrick68]

Thanks for all your advise,looks like the problem is solved.

After reading various threads on this site I changed the "Thrust Sensor", but the problem remained.
Tonight I finally got around to fitting a "Turbo Pressure Converter Valve", this seems to have resolved the problem with the intermitant boost.

Now the turbo is giving boost as before, but now very smokey. Is this due to not running properly for a while or do you think I have further problems with the Turbo?

[xpro]

also there is boost solenoid valve attached beside timing belt cover,infront of the turbe where all the vacum pipes go.That my be the problem aswell

[Mike McKinstry]

Hi, can someone just confirm the names and locations of these sensors please as some seem to have a number code i.e. n75 and others referring to these parts by description.

many thanks,
Mike

[ini]

The 'pressure converter' or 'N75' is an solenoid valve that converts the electronic control signal from the ECU, into the 'pneumatic' variable vacuum or pressure that directly controls the turbo or wastegate actuator.

It simply mixes fresh air with vacuum for VNT turbo's, or pressure for external wastegate turbo's, controlling the variable vanes/wastegate movement.

On inline engines, the 'N75' is located at the front of the engine/bay.

On a transverse engine it is generally located at the rear of the engine on the bulkhead, next to the similar EGR control valve 'N18' which is always located at the rear of the engine bay on 1.9 VE engines.

The 'thrust sensor' is the boost pressure sensor or 'MAP', and on all but the early cars measures charge pressure and temps.

[Mike McKinstry]

Having changed MAF/MAP/N75/new temp guage fitted as was sticking/checked movement of actuator to cure 17965 overboost intermittent code car has been running well last week or so apart from gradual acceleration 40-60 up a fairly steep m/way slip road which when cold car will always go into limp.
Does the fact that limp almost seems inevitable if trying to accelerate when guage is cold give any clues to anyone what is causing this or does it confirm sticky VNT.
Usual off/on at next slip resets and all well again although obviously engine is by now warmer.

regards,
Mike

[passat 130 tdi]

my car was going limp when cold , i got some 10k boost spray from ebay for diesels , sprayed it into turbo pipe and the car has been fine ever since , i was turning off the ignition off then back on and jump starting the car whilst rolling along to clear the fault , never did it once warmed up . i also checked the terminals on the n75 valve and they were very green , cleaned these up also .

main cause is carbon on the ring and vanes stopping it from returning and therefore leaving the actuator stuck and not knowing what to do , causing over boost .

[Mike McKinstry]

Can never understand how this 10k works as is only cleaning air "clean"end of turbo not dirty side -were you getting probs when warm as well?

Mike