limp mode

[crunchynutter]

Hi guys

Typical is'nt it, just ordered all the bits i need to change the cam belt (£200) when on my way home from the curry house last night my passat tdi130 sport engine code AVF went into limp mode, i did a scan on it and it threw up fault code 17965 charge pressure positive deviation, after a quick search on this absolutely marvellous forum possible causes are split hoses or stuck vanes, after a visual check the hoses all seem to be fine, but what i did notice was the egr valve (i think thats what its called) does not move on start up or shut down, is this causing my problem if so what remedy would anyone suggest apart from replacing the valve

Thanks for any info

[martin1810]

Are you sure you are talking about the egr valve. The egr valve can't cause overboost. The most likely causes are faulty MAP sensor, faulty N75 solenoid or stuck vanes in the turbo.

[ad777]

hi if you read my thread,power loss replace map,just a couple of threads below yours, i have had the same problem,and so have hundreds of other people apparently!have had lots of suggestions,but seems to boil down to what martin says,map,n75,sticky vanes.am going with map first on friday as it easy to do and quite cheap!if you get yours fixed before the please let me know!!cheers adam:biglaugh:

[crunchynutter]

Martin
im not sure if it is called egr valve, its the one as you look at the engine on the left side towards the back, in two parts one of which is visible through the plastic engine cover the other part you can see from the side of the engine and has a vacuum pipe to it and a 4 inch approx lever. is this the egr valve or n75.
adam if i have any luck resolving this problem i will let you know.

Ta for your help
Edit;
just done a google image search and the part im talking about is the egr valve, or at least part of it, what im talking about is the part that is supposed to move when you start or stop the engine,i beleive it releases pressure so as the engine stops smoothly if this lever is stuck open or closed will this cause overboost

[martin1810]

Sounds like you mean the anti-shudder flap. That is meant to stay open all the time the engine is running. It flips shut for about 3 seconds when you switch off and then opens again. That can't cause overboost as it is meant to be wide open at all times.

[crunchynutter]

Thanks Martin
As usual you are spot on
is there any way i can narrow down the possibile causes of the limp mode.
i have vcds lite and a limited knowledge of how to use it, can i diagnose a faulty map sensor or n75 solenoid, or is it a case of replace the cheapest part first and see what happens

Cheers

[martin1810]

have a look here. This will give you a clue about checking things with VCDS.
https://sites.google.com/site/1810martin/vcds-and-pd-tdi-engine-health-check

[crunchynutter]

Martin.......top man:biglaugh:

You seem to have an endless (was going to say encyclopedic but couldn't spell it) knowledge of all things passat.
I know where the map sensor is and the maf sensor, thanks to you i now know where the egr valve is but whereabouts is the n75 located, ive read somewhere its front left as you look at the engine but this is a bit vague. As i mentioned in the op im about to do the cam belt so the fronts coming off would that make it easier to find.
Thanks for all your time and help

[martin1810]

Locate the turbocharger actuator. The round blob that connects to the turbocharger vane actuator arm. This round blob has a vacuum pipe going to it. Follow the vacuum pipe. The next place it stops is the N75 valve. The N75 valve will have 3 pipes connected to it. One of them goes to the air filter. That shows you have found the right solenoid. The EGR solenoid looks identical to the N75 which can be confusing. I am sure there are pictures on here somewhere. You could do a search.

[ad777]

hi just replaced map sensor and car back to normal!!!worth a shot as a first resonably cheap option.good luck,adam

[scotty33]

have a look here. This will give you a clue about checking things with VCDS.
https://sites.google.com/site/1810martin/vcds-and-pd-tdi-engine-health-check

Incredibly helpful stuff there Martin Thanks for taking the time to write it up! :beerchug:

[ad777]

did u manage to sort the problem?

[crunchynutter]

Think so
Replaced MAP as suggested, and just because they looked as if they needed it i changed the small vacuum hoses and re-checked all the other vac pipes. About 2 months ago i changed the injector loom and i think i upset the sensor then, fingers crossed its back up to full power and no more limp mode or codes recorded.
Thanks for all replies :D