1995 850T CEL on, keeps throwing codes 443 435

[2012]

Does anyone have an idea why the codes for O2 sensor and Cat inefficiency keeps coming on? Also I get code 143 often, knock sensor. Car runs like the cats meow with 147000 miles, but these codes come on all the time. I do smell a foul odor when I let the cat out of the bag(WOT), but no drivability issues. Thanks in advance

[phils94850]

If your getting a bad smell more than likely you have a bad CAT which is why your getting the o2 codes.

[Volvofan94]

My thought would be to replace your front O2 sensor and see if it clears both codes (if it hasn't been replaced recently).

My 94 850 Turbo was throwing the 143 code for a while earlier this year. I would reset the code and it would come back a few days later. A long story short, after doing a tune up on the car, I eventually found out the intake manifold gasket had torn completely through below cylinder 5 causing an air leak. I went out and bought a genuine Volvo intake gasket and the code hasn't returned since!

When the car threw the 143 code it was in the mix of other codes too. I corrected the other codes first which fixed the 143 code. I don't remember the codes exactly, but a misfire in cylinder 5 and three way cat damage were in the list.

-volvofan94