My check engine light recently came on, along with oil low level symbol. I am still about 500 miles and 3 weeks away from a regularly scheduled oil change. When I remove the oil cap, the noise stops.

I ran a diagnostic scan and got the code "P0171." Based upon some research online, it seems like it could be the PCV breather box.

However, I also ran to Autozone and let them run diagnostic on it as well. Autozone's scanner said a Mass Air Flow Sensor was most likely the option.

Any thoughts?

 

1st I got suddenly high oil consumption about 1L per 1500km on my 2016 XC90 at 125000km
few weeks ago I got engine code P0171 which is LEAN GAS ON CYLINDER 1 . i suspect bad Cylinders or cylinder rings. i also found out unusuall state of PCV box after removing it.
check pictures. I fixed the issue and waiting to see if it helped.

 

jacek_canada - I think I might dealing the with same problem. code P0171. Question - What did you see that was unusual in the PCV box/oil trap? Was it the thin metal plate? It looks like you've replaced it or got a new PCV box Did it solve your issues? Did you also replace the PCV diaphragm?

Thanks - mawilber

 

some times its the valve in the PCV that can stick, sometimes its the diaphram that can tear. As to the P0171, that's saying the fuel trim is lean - which can point to an air leak, incorrect fuel pressure, an issue with other sensors ie O2 sensor, MAF, fuel pressure sensor etc. If you suspect the PCV, best to inspect/clean the intake path to make sure oil didn't get onto the MAF etc. You can also pop off the oil separator to inspect as well.

 

This P0171 is frustrating me since it can be so many different things. I inspected the PCV diaphragm and it looks to be intact. I inspected and cleaned the MAF sensor. Code P0171 returns after I try to clear it immediately. So much for it being something simple. Car is running perfectly fine, only difference I can appreciate it that the exhaust smells a little like gas. Next I'll be taking the oil trap off with plans to replace if I can appreciate any problems/damage.

I keep you posted.

mawilber

 

after I unscrewed the OIL TRAP / PCV box i found that both metal plates / valves were detached from their original locations and were lying on the bottom of the PCV box. I am not sure if they were not installed properly at the factory or they were blown with high air pressure because other component failure.
I put them back and locked them in place. After tthat my ERROR P0171 went away after that BUT week later came back I got CHECK ENGINE LIGHT AGIAN . I have to see if it happned agian or something else happened and I will report back in a 14 days since I am away now. I am also planning to check compression at each CYLINDER and see if I have in fact PISTON RING problem.
my 2016 XC90 is at 122700km now.

 

I replied below, Thanks for checking with me on this issue.

 

I'd suggest two thing 1) replace the PCV oil separator with a new unit. If something "falls out of place" - well that's not supposed to happen and the part is failing and will eventually again 2) you may have something else going on that caused the part to fail. Before replacing the part, I'd have a shop do a crankcase pressure test (or do a rubber glove test to see if there's excessive pressure or vacuum). It can't hurt to do a compression test but I doubt if that's related, particularly if you don't have other symptoms like oil consumption, hard starting, fouling plugs, smoke on deceleration etc.

 

Hi, I just got a 2016 Volvo XC90 with 161,000 miles and got same check engine light with lean code. Aside from replacing or cleaning the PCV, any other solutions you can suggest that might help? Thank you and have a great day.

 

as I remember it, mine needed a new O2 sensor at the dealership. I’ve since sold the car.

 

Get a new oil trap for $40 on Amazon and see where that goes.

I had the P0107 code for months and the stealership wanted $500 just to diagnose it (gave me the old spiel of "well it could be anything, so we have to check everything" nonsense). Well when the car started squealing at idle, I was told by someone on Swedespeed to try replacing the oil trap. I did and VIOLA! - no squeak and the CEL is gone (had to disconnect the battery for a few mins).