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XC90 random P0420

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
CleVolvo1
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XC90 random P0420

Post by CleVolvo1 » Thu Nov 01, 2018 1:26 pm

Good Day all,
I have a 2011 XC90 with a 3.2 and 145,000 on it. It has had two owners prior and I believe the previous was the type to not maintain the car. The car runs and drives great and is very smooth. However I am getting a random P0420 error. So I have done the following so far:

Oil change = oil was jet black and thick such as 20w-50
Replaced oil filter
New air filter = clogged and dirty
I cleaned the MAF sensor = was dirty
Ran smoke tests from smoke machine on the intake manifold and exhaust tail pipe = no leaks anywhere either direction
Inspected down flow oxy sensors they seemed ok.

I did notice the tail pipe had some black soot inside as if the car was running rich.

After doing the tasks I listed above I connected a Snap On scanner and recorded the engine data. I took it for a drive on the highway and left it in 3rd gear accelerating (WOOT) to 70MHP and coast down to 50MPH and repeat for several miles. I can email the file SCM for anyone to review just contact me. I have uploaded two photos from 10/31/2018 and 11/01/2018. The SCM file maybe more useful for people who have ShopStream Connect.

I am looking for anyone to find something I am not seeing. Maybe there is an underlying issue or this car needs the classic workout; such as fill up with good fuel and WOOT the hell out of it, hopefully this will also blow out the CATS, and drive it around for some time.
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SuperHerman
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Re: XC90 random P0420

Post by SuperHerman » Thu Nov 01, 2018 2:10 pm

Can you rerun the tests and have Bank 1 Front and Rear O2 then Bank 1 short and long term fuel on one page.

Page 2 same format but with Bank 2 info?

Grouping them like that will help identify a faulty O2 sensor or point to a possible air leak (which your smoke test didn't show).

Any other info like mileage and spark plug condition? When does the car code - time, usage, throttle position or as you say totally random (maybe bad connection?).

It is hard to track as the eyes are not what they were and I have to scroll up and down. Your testing is on the right track though.



CleVolvo1
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Re: XC90 random P0420

Post by CleVolvo1 » Thu Nov 01, 2018 2:23 pm

Sure. I added trim graphs for both days. The vehicle has about 148k miles on it. Sparks plugs are unknown I have not check those yet.
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SuperHerman
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Re: XC90 random P0420

Post by SuperHerman » Thu Nov 01, 2018 3:24 pm

Take a look at these two articles.

http://www.smogtechinstitute.com/smogte ... elTrim.pdf

https://www.autoserviceprofessional.com ... you?Page=2

http://www.smogtechinstitute.com/smogte ... elTrim.pdf

Your data is pretty close to being within spec. I noticed that in Column one in two instances the Rear O2 sensors are reading "0".



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SuperHerman
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Re: XC90 random P0420

Post by SuperHerman » Thu Nov 01, 2018 11:12 pm

I looked over the data and did some reading. It looks like everything is operating as it should. The values are actually pretty good and nothing is out of wack. It appears that the O2 sensors are performing their function correctly. Fuel trims seem to be under control so the system is working. Have you looked at the actual O2 sensors to see if they have been changed? It would not surprise me to see they have been changed in an effort to fix the problem. Worth a look and would be a clue.

Another thought here - if you examine the O2 sensors make sure they are a quality brand and the proper part number. I had a "bad cat" episode on a Subaru which ended up being a counterfeit O2 sensor with a fake Denso logo and part number. I had to download the shop manual and meter the connections. This was after the dealer told me the computer was bad (replaced it with a used one) as I already replaced the cat. Once I replaced my new "fake" O2 sensor problem was solved. Expensive lesson.

As far as random - is the random every other engine cycle (on-off) or is it truly random?

Next thought would be to actually get an exhaust emission reading and see what it says.

I would say at this point, based on your homework, everything points to what the code is telling you - a bad catalytic converter. This could be why the prior owner got rid of the car.

Most likely - like you - I am not willing to throw good money at a cat which may be good without doing more testing and driving more miles.

As cats are pretty expensive I would take the long term approach. Add some injector cleaner to the gas, run a higher grade gasoline, replace your spark plugs (as you will be pulling them anyways) and clean your exhaust tips (so you have a visual base point). Basically you want to get the base items in order so you are confident moving forward. Then I would drive the car and be on the look out for excessive oil consumption, puffs of smoke and anything else you can monitor. Make sure you get it good and hot with some long spirited drives. Maybe just maybe this could clean up your cats especially if the prior owner just used it on short trips and shut the car down. Meanwhile, you want to gather as much info as you can over maybe 1000 miles, more would help if you are watching the oil condition and changing it. As everything seems to be working right, except your cats, you shouldn't be hurting anything. I am not a fan of the cat cleaner some places sell. Getting the cat up to good operating temperatures for extended periods should do the trick - if the trick will work.

During this process I would try to figure out what has caused it to fail (if in fact it is bad). You are looking for excessive oil consumption on Bank 1 - so an easy place to start is with the spark plugs. Remove them and see what they look like compared to Bank 2. One would think that they should be "oilier" than those on Bank 2 (or at least one of them will be). Next would be a leak down test to try and find the cause of the excessive oil burning, assuming this is what is hurting your Bank 1 cat. You could have ring problems, valve seat issues or valve stem seals that are worn. A few oil changes, shortened intervals, could unstick some gunked up oil rings.

I am guessing everything will test out pretty good for a car with your mileage and you have a bad cat. Still you have some easy items like spark plugs, injector cleaner and spirited driving for more miles before replacing the cat. Your ownership of the car has been too short to really know what is going on.

During the process maybe look into finding a low mileage used cat and try your luck. You may get lucky and find one on Craigslist.

One last thought. On my BMW X3 I had a similar issue. After much research and O2 sensor changing I learned BMW had a software update that would "widen" the parameters for the emissions. The original factory parameters were too tight and didn't compensate for normal engine wear and when the cars were hitting 100k or more too many were coming in for service. Exhaust tests showed the emission output was totally acceptable under applicable standards so the software was adjusted to essentially allow higher mileage engines to pass. Dealer didn't think it would work, and $75 later I have had no issues over more than 40k miles. Maybe Volvo has something similar. Worth a phone call.



CleVolvo1
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Re: XC90 random P0420

Post by CleVolvo1 » Fri Nov 02, 2018 9:00 am

Thanks for your help I will go about the procedures for the car and I will post my finds. If anyone else has info please feel free to share.



jpbrooks81
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Re: XC90 random P0420

Post by jpbrooks81 » Fri Sep 27, 2019 6:44 pm

I have the exact same car with the exact same problem. I'd love to know if you ever found out what was causing the issue. Did it turn out to be a simple software update? Please let me know. The issue is driving me nuts. Ive read a lot of posts about this, but no one ever says what they did to fix it.



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