2011 XC90 3.2L P0420 P0430 P0171 and P0174

[Dust101496]

Hey guys I've got some kind of vacuum leak or just bad sensors here and could use some help/opinions. My xc90 3.2l has less that 93k miles on it and it's at first started throwing a code P0430. The engine light would randomly come on and off. Then it started throwing a code P0420. So immediately I thought ok so one 02 sensor went and then another. I put it on the back burner but did an oil change. My dumbass left the oil cap off for atleast 2days during the week until I pulled in the garage and saw it. I put it back on, checked my oil which was good then decided to scan my car again. I got the 171 and 174 codes on top of the older o2 codes. I reset the codes and hoped the new ones wouldn't come back. But they dide. So I decided to just look around the engine bay a bit and found nothing...except that when I pull my oil dipstick I get a honking/goose sound? Like a constant GOOSE (the waterfowl) sound. Never heard that in my life...I'm thinking PCV system? Is this bad and mean I need to replace it? Also, any ideas about my 420 and 430 codes? I don't seem to have an exhaust leak and the fact that it goes away and comes back makes me think it's a sensor but before I end up replacing all 4 I'd like to exhaust all other options...no reason to throw parts at it right? Thanks guys!

[generic_volvo_driver]

You're right about the PCV - it's super simple: https://www.youtube.com/watch?v=J7KROLIZpas

Do you have access to VIDA/DICE - that may reveal much more information what's going on...

[Dust101496]

So could my MAF sensor be going as well? Because I cleaned all my intake sensors and they were clear for about half a week and then I started getting codes again...I looked at the pcv system and it's appears fine, couldn't find any tears in it which was odd because of the goose noise.

[ChitownV]

How did you check the PCV system? Did you unscrew the dozen or so screws and cut open the diaphragm cover? One way to diagnose a bad PCV is the exact sound you are hearing when the dipstick is removed with the car running. The PCV can also cause poor running issues you described because vacuum is affected. At 93k miles, it is around the typical lifespan of the PCV.

Not sure if generic codes can see the MAF, but in VIDA the MAF would throw its own codes. O2 sensor codes doesn't mean a sensor is bad. It means the O2 is reading a bad air/fuel ratio, efficiency, or combustion and it is out of a range in what deems normal.

Based on what you have described, I would change the PCV first and then go from there. It is a simple swap and the part costs what a Volvo shop would charge for one hour of labor.

[Dust101496]

So my codes keep coming on and off, car runs great tho. I can try to post some pics of my O2 sensor readings but I know how to read them myself. I think my driverside o2 downstream is going out and my passenger side upstream as well. Which bank is driverside and which sensor is indicated as 1 and 2? My scanner reads one type as volts and the other as mA. Results as follows : B1S2_.830v B1S1_.004mA B2S2_.805v B2S1_-0.035mA. Also, my car doesn't make any noise at all now when I pull the dipstick while running? All I did was pull the plastic snap cap off the PCV system (right side of the part with 12bolts) and inspect the rubber for tears. Why would my car sound like a goose for a second and then never again? On another note, when starting it up today after work it took about 40min for the car to come up to temp. It was 10degrees out but that sounds like a stuck open thermostat to me. Any opinions?

[ChitownV]

Well, it sounds like the thermostat is sticking. But double-check electrical connection is secure and you could even very lightly tap the thermostat to see if that will close it. Could a stuck thermostat cause an emissions efficiency code to pop up...possibly. Coolant temp is factored in for engine running.

Out of curiosity, what is the history of the car and its maintenance since there seem to be several different issues? Are you checking and reading when the engine is at operating temp, cold, etc. I ask because, with codes and conditions, some background is helpful, like when it started, maintenance history, what led up to it, how many times does something occur, etc.

For the O2 sensors, I look at the voltage as well as the voltage behavior, then factor in things like load while driving, idle, coasting, blipping the throttle, etc.

Lastly, I never checked my old PCV if the diaphragm cover popped off, but on other makes, they are usually sealed.

[Dust101496]

I am the second owner of the car, first owner used it as a family car and maintenance records show it was mostly serviced at the dealership. One strange thing in the records tho is that it had the computers checked, wiped, and reprogrammed as if the electronics went haywire. I haven't had an issue really except one time where the car had no power at all and I jumped it and everything was fine since. And ive been looking at the activity graph for the O2 sensors, my downstream don't look at smooth as they should. But I'm not getting a code thrown...I'm starting to think I got some bad gas on base at the BX and since I refueled at a Exxon I haven't had a single issue.

[ChitownV]

So, next time maybe wait to see if you have a pattern of an issue before posting. Acute things happen, like when the temps get low or as you may have had bad gas.

Knowing you just filled the tank may have helped with understanding what had happened, so a pre-cursor or more background information of what led up to an issue helps.

Here's to hopefully having a mostly trouble-free XC90 (except for regular maintenance, lol).

[Dust101496]

My xc90 was far from trouble free lol. I had to replace 2 wheel bearings, a battery, cabin air filter (didn't fix the AC smell), and replaced 2 O2 sensors. All within a year of owning it. Bad luck for me I guess! I just traded it in for a nice Audi S4. I don't want to fix odds and ends anymore on my daily. Thank you all for you help it was fantastic. Btw, after replacing the O2 sensors my car showed that that cats were starting to go out and I never mentioned it, but my torque converter was starting to slip which is a known issue. So I dodged a cannon of costs 😁