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P0234 Turbo Overboost/oil leak?

Old 09-27-2012, 09:24 PM
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Location: Wisconsin
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Default P0234 Turbo Overboost/oil leak?

Hey Guys!
I have a 1999 Volvo s80 t6 with 191,000 and I think its finally starting to show it's age. After giving it an oil change yesterday, the check engine light have on with the P0234 Turbo overboost condition code. In addition, it goes into limp mode (Only in 3rd gear) and has developed an oil leak.
I didn't do anything out of the ordinary with the oil change, used 5w-30 oil, stock filter. I don't think I bumped anything. I did notice after 1st startup, oil leaking from the filter canister, but after a couple re-screwing tries, it stopped leaking. I plan on jacking the car up again tomorrow, cleaning and then try to diagnose the leak.

So, question, could the oil leak be related to the P0234 code, or is it just an unhappy coincidence that both things are going wonky? Any other causes for a turbo overboost condition besides a turbo check valve?
Any advice/input would be very much appreciated. Im trying to get her to 200,000 and beyond.

Old 09-28-2012, 08:14 AM
Join Date: Aug 2012
Posts: 60

Overboost warnings are prominant in volvos as well as audi I think, and most always involve the wastegate, so I'd look into that or let I volvo monkey check it out at the dealer. As for the oil leak.. Ya got me. You seem very competent, good luck
Old 09-28-2012, 02:39 PM
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Turns out its the oil filter canister again. I thought it stop leaking. Anyone have canister leaks? Solutions? The o ring gasket looks ok. Should I just get another filter?
Old 09-28-2012, 06:17 PM
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BAM. New filter, new gasket, problem solved. Still probably need a turbo check valve.
Old 10-12-2012, 01:04 PM
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Posts: 171

Lots of things could cause an overboost code. Faulty boost pressure sensor, faulty compressor bypass valve, faulty (or maladjusted) wastegate actuators, stuck wastegat as well as any of the associated vacuum piping with these parts.

Before you write off the actual valve itself make sure ALL of the associated pipes are in good condition. Follow them back to the metal part, down to the each of the turbo wastegate actuators. If all the vacuum piping seems good, you can try "exercising" the TCV with some solvent in it to free it up.
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