P0420 wth catalyst gutted out
 

2000 Blazer 4wd with gutted cat converter.

I installed all 3 AcDelco sensors a year ago and truck running fine.

Yesterday out of nowhere I got service engine light. I used ELM327
scanner and its giving me P0420. (catalyst efficiency below treshold,
Bank 1). Which sensor is that?

What should I check first? Am mostly a noob!

Can I still drive around neighborhood?

the code means the catalytic converter isnt cleaning your emissions. If it's gutted then you should get that code becasue it doesn't filter. The downstream o2 sesnor is the one that detects this.

change the cat. simple as that.

I have been driving for little over 1 yr with converter gutted out
and new sensors installed. I was not getting lite till now. If I should get that
code as you say, then I would have gotten it same day I installed the
sensors.

thats pretty much it, thats crazy that it didnt throw that code sooner, i have seen this once before on a cat that had the o2 sensor screwed into the side of it all the honeycomb part was busted and missing before the o2 sensor and no code.

you can try changing out that sensor after the cat and see if that helps. good luck

maybe you just got lucky? Personally I've fooled o2 sensors before. And exhaust leak can falsify the readings as well. Gutting the cat makes the cat not work and p0420 means the cat isn't working. It is nothing more than an emissions problem. You will experiance no drivability problems and it will only effect you if you need to pass and emissions inspection. It will only hurt the environment, not the truck

And it passed the emissions test on 1st and only try.

But am happy to know it wont hurt the truck.

Computer will try to compensate for the loss of back pressure, in which case you will loose power and your MPG's will fall like a rock because the computer will just dump fuel into the engine to try to restore the pressure.
A good cat-back setup is a good way to get the best of both.

With the efficiency of today's catalytic converters there is no logic to gutting one, removing one, etc. Replace the cat.

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