P0299, Possible causes?

[usaf655]

Good evening everyone, So my car has the terrible P0299 Error code. Ill try to list all relevant (or possibly) relevant info.

-Sometimes (before warming up to running temp) the car will hit full boost
-Car jumps into limp mode, randomly, I could be in park and then go into drive and itll go into limp mode. Or I can be on cruise control, turn it off and attempt to accel. and see the car is in limp mode. But occasionally, not often, itll begin to run normal again. When in limp mode, the car will only run up to 5Lbs of boost.

BRAND NEW PARTS IVE TRIED (less than 5000 miles on these)
-Diverter Valve
-PCV Valve (not the breather hose though)
-N80 valve, 10k miles ago

Mods
-APR carbonio intake
-034 Test Pipe

I do not have a RossTech cable sadly. The car will be taken to the stealership this weekend, I plan on doing a boost test on the lines to check for a leak as well. Just curious if you gear heads may have an idea of whats left that may be faulty. I just really hope I wont be flipping a turbo rebuild bill.

[Sanjman]

Everything. Stop throwing parts and get the smoke test done.

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[djhemmen]

When my car had the exact same symptoms you are describing it was a bad boost solenoid (N75). It worked intermittently so it was tough to diagnose. Once I replaced it, full boost all the time. I got it from ebay for $35 shipped.

[usaf655]

Thanks, if the leak test runs no leaks. I plan on just having them replace my N75 solenoid.

[RakkCity]

it could literally be anything, so best to have some diagnosis done before throwing parts at it. My 0299 was due to a worn LPFP that was cutting fuel, accompanied by an intermittent 310B code as well. Other causes are the N75 wastegate solenoid, leaks in the intake tracts, bad valve cover, PCV including breather tube, bad turbo, dirty or faulty MAF, the list goes on and on.


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[lococo72]

Gents if I use Ross tech vag com cable would it let me know exactly what's wrong and what I need to replace mine is kind comes and goes on the winter the check engine light just goes off and once the weather start warming up check engines comes back up
I don't trust stealership that much when it comes to diagnosis ?


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[djrdsmusic]

Good evening everyone, So my car has the terrible P0299 Error code. Ill try to list all relevant (or possibly) relevant info.

-Sometimes (before warming up to running temp) the car will hit full boost
-Car jumps into limp mode, randomly, I could be in park and then go into drive and itll go into limp mode. Or I can be on cruise control, turn it off and attempt to accel. and see the car is in limp mode. But occasionally, not often, itll begin to run normal again. When in limp mode, the car will only run up to 5Lbs of boost.

BRAND NEW PARTS IVE TRIED (less than 5000 miles on these)
-Diverter Valve
-PCV Valve (not the breather hose though)
-N80 valve, 10k miles ago

Mods
-APR carbonio intake
-034 Test Pipe

I do not have a RossTech cable sadly. The car will be taken to the stealership this weekend, I plan on doing a boost test on the lines to check for a leak as well. Just curious if you gear heads may have an idea of whats left that may be faulty. I just really hope I wont be flipping a turbo rebuild bill.

My 2007 A4 B7 is having the same issue, car goes to limp mode (under 5psi) when engine warms up.

[Older_not_Wiser]

N75 - Had same issue (low boost when engine warmed up), did a bunch of diagnosis and it pointed to N75. I put all the diagnosis steps in a post in another bigger P0299 thread.

Linky
https://www.audizine.com/forum/showt...1#post12724091