O2 Sensor Question
 

New poster with a 2012 XC90 R Design. I have the P0420 and P0430 codes and I'm trying to determine the potential issues. Unfortunately I have no history since I recently purchased the vehicle. I have read up on the issues and fixes but have a question about the O2 readings that I am seeing. I would have expected to get the same information from both sensors. Is this normal or should I start with replacing the sensors.

https://cimg2.ibsrv.net/gimg/volvofo...1513440f50.jpg
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Your codes are catalyst efficiency codes - the O2 sensors are sending signals that there is too much oxygen left at the rear sensor/s after combustion and the cats have done their job. (converting HC, CO, and O2 into H20 and CO2)

So generally - 420/430 codes are not caused by bad sensors, they are caused by something else. (most commonly a bad cat)

These codes could very easily be why the car was for sale. Previous owner did not want to buy replacement Cats - they seem to cost between $1100 - $1900 each (they're part of the exhaust manifold and there's 2)

How many miles on your new car?

Is there any way to tell which cats are bad? I believe there are four cats and sold as three assemblies ( cyl 123, cyl 456, and the two downstream cats that include the flex pipes).

Also, the pricing seems much higher than what I see. I assume you are talking installed cost? I have no problem doing this type of work in my home garage.

The converters that can be checked for efficiency would be between the front and rear sensors. Those are the manifold converters. I just googled those part number to get representative prices. Don't know if you have a 6324s or 6324s5



https://cimg6.ibsrv.net/gimg/volvofo...c1d2b4de3b.jpg

I can confirm what @hoonk says about cost; OEM Volvo exhaust manifolds are selling for $1100 - $2000 EACH. I've spent the last hour scouring the web for alternate suppliers because I'm having the same problem (P0430 code) and I can tell you there are limited options. Here's one example of an OEM Volvo replacement (bank 2 / left / driver's side.) This is the cheapest OEM Volvo replacement I've seen, at $1,133;

https://parts.volvocarsannapolis.com.../36000170.html

There are other options, some listed below, for less. Caveat; They are clearly inferior quality but if it does the job, you might consider one of them.
(I'm looking for bank 2, which is why these are all the left side.) p.s.; I don't know if these are the same for your car... You'll have to enter your own car's info.

https://www.carid.com/2011-volvo-xc9...638201080.html
https://www.carparts.com/details/Vol.../DAV17293.html
https://www.hottexhaust.com/volvo-xc...oaAieQEALw_wcB