P0420 code
 

Hello!

My check engine light came on and after scanning it I got the lovely P0420 code (Catalyst System Efficiency Below Threshold)

I don't believe my cat is shot because I haven't noticed any power loss or weird smells coming from the exhaust.

Could I be so lucky that I only have a bad o2 sensor?

I have reset the code twice but it seems to come on after driving 60 miles or so...

Thanks for all the suggestions in advance :)

Hello ,first thing to ask is does your car only go on short journeys ? , If so I would suggest 30 -40 minutes driving at 60 MPH ( 100 KPH ) to burn off any built up deposits on matrix . I see this issue many times when performing an MOT test (an annual safety inspection in the UK , your equivalent is katsastus i think ) .

The increase in heat & gas flow should burn off any deposits on the matrix , allowing it to work more efficiently . If you have or know someone who has a dealer level scanner or similar , look at the signal pattern being generated . The waveform should change quickly & slightly , the tips of the waveforms are close together , failing sensors become deeper & farther apart as they fail to react quickly enough

Hope this helps

The car is driven almost daily and the trips usually are about 30-40 minutes long with speeds over 60 mph.

I do not have access to a proper scanner to look into the o2 sensor wavelengths.

I have a parts car s40 2002 which I could use to get a spare catalytic converter from but I'm concerned if it fits the v40 exhaust or do I have to weld it in.

No idea if it's just a coincidence, but mine was throwing this code even after I changed the catalytic converter (it was knackered in my case, I already knew that) but I cleaned my maf and also my map sensor with contact cleaner, and I've not had the code come back in over 500 miles.

I said earlier on this thread that I didn't have any weird smells coming from the exhaust but on a further inspection I'm noticing a smell of unburnt gas when coming to a stop for example on a stoplight.

Did you notice anything similar when you knew your cat was a goner?