Hi all,

my 2009 TSX 4cyl with 160K miles threw this P0420 catalyst system efficiency below threshold bank 1 code. Car runs great. Took it into repair shop. They said they want to replace A/Fuel sensors & HO2S sensor AND catalytic converter to the tune of $1300!!!

My experience is to replace one item at a time I.e O2 sensor first then run and evaluate. It it wro g for them to want to replace everything at once?

thanks in advance
jerry

T

 

If you're on a budget I'd put an extender on it an call it a day - - Might need the 90 degree one, i'd double check.

All of the things you have listed here you can replace yourself in your driveway by the way.

 

That's a crock of crap. Don't worry about the upstream sensors for now. Based on my experience, the P0420 and P0430 codes are due to goofy downstream O2 sensors. I've had the issue on my TL and Pilot, both of which went away when I replaced the O2 sensor. The P0430 code is for bank 2 which you won't have on a 4-cyl TSX.

The upstream A/F ratio sensor is more expensive, and will throw a code of its own if it's defective. Yes, it can potentially cause the downstream O2 sensor to freak out a bit if the A/F ratio is wrong, but in that case you'd also typically experience reduced fuel economy and/or power output since a goofy A/F ratio is likely to cause one or both of those issues. If the car runs great and gets the same mileage it's always gotten, don't worry about the upstream for now.

I agree with the extender option as a start, since it's cheap. If that doesn't work, get a new downstream O2 sensor. I've just gotten generic ones from eBay or Amazon since they're cheaper. But you can opt for the OEM one if you want. It's a bit more expensive but still <$100 I believe.

 

+1 on downstream..

 

Thanks everyone for responding. I'll try out the o2 extension first.