My car is a Volvo XC90,2011,3.2, 176,000 miles, everything works very well and the engine performs well, except Check Engine Light is on, the code is 420 related the Cats and I have replaced both cats (brand new, aftermarket, 5 years guarantee)and two sensors on bank1 side, things get better but CEL is still, comes on and disappears automatically, probably once a week, always the front O2 sensor problem, and I have changed it twice. The technician told me, it's related to oil burning of the engine, which damaged the sensor even the Cat convert. To try to figure it out, I went to official Volvo car care center, the advisor there told me the real problem is the aftermarket Cats I used, which is defective, no great importance to the engine burning, by the way, the engine consumes 1quart every 2000 miles, which is normal according to Volvo car care center said. Also, Volvo told me, I have to redo it, by using original Volvo parts, which will be a huge cost. My question are: 1.Does engine burning oil damage the sensor and Cat Converter? Is it a big deal? 2. Aftermarket parts match my car? 3. Do I have to Chang my engine, other options?

 

Appreciate all for replying, advising... I am waiting for...

 

I also have a Volvo XC90,2011,3.2, with ~75,000 miles. Got the low oil light this past weekend. At the dealer now. Was told oil consumption is a known issue with Volvo and may need a rebuild, possibly at Volvo expense. Also switching me to synthetic. Burning this much oil is not normal.

I didn't answer your questions, but hopefully helpful.

 

i have an 2001 s40 i got the 420 code as well and i had oil burning i noticed that one of the lines of the oil cooler is leaking oil from a clamp that was tightened to tight and causing it to tare and i have leaking oil from the vvt solenoid in which i replaced the gasket and its still leaking, but coming back to the code i cleaned some of the oil that was covering my o2 sensor (upstream) then i used a higher octane grade (89) of gas just short of half tank and i drove my car for a couple of miles and code went away and it still hasn't come back on. hope this helps