I've got a 2006 honda crv SE auto. I'm trying to get it inspection ready but it keeps throwing p0420. I've addressed the obvious issues from the trash shop I got it from. I fixed their atrocious "welding" job on their half-assed exhaust fix,the cat is new and the o2 sensors are new. I did a vacuum test to find leaks and even replaced the pcv valve and hose to eliminate potential exhaust contamination. Here's where it gets interesting. I check the readiness and I've got the green light across the board including the cat. Despite this, p0420 is still there. I did leave it there after the pcv valve was replaced to see if it would clear itself. Should I clear it and let it go another cycle or is there something else going on? Any ideas would be helpful.

 

Are we supposed to know what this is?

 

welcome to the forum. you mentioned the cat and sensors were replaced. were they after market sensors and cat.? asking because it it came from a Trash Shop, they put on normally after market parts. Honda's don't like after market parts. the cat is 1800.00 and the after market sensors are denso type but Honda mods the sensor to suit their vehicles not multi use type.

 

I addressed the issues that were obvious to me. Like the half-assed welding they attempted. They hacked off the post cat flange and "welded" the cat straight to the resonator pipe. They globbed on hemorrhoid looking tack welds on the bottom of the pipe and packed the massive gaps in the top with some kind of flaky sealer crap that immediately fell off. It was leaking from everywhere. I addressed this issue. I ground off and cleaned up their mess, rewelded it properly, replaced the other 2 donut gaskets pre cat and post resonator and did a vacuum test to check for pinholes.

I eliminated all exhaust leaks.

 

Who made the cat and O2 senors?

 

Would clear the codes and run the vehicle to see if it comes back.
If it goes green and no new codes then you are all set.
If the code comes back then should revisit the definition of the DTC.
It might give you a new perspective.

 

I couldn't tell you who made the parts. I didn't buy or install them. According to the dealership "some crackhead came into the lot and hacked off the original". Judging from the "work" they did on the exhaust I'm sure they aren't even mid range parts. If they couldn't take 10 minutes to properly weld anything or better yet just replace the resonator pipe instead of hacking off the flange on the new cat, I'm sure they didn't invest much.

 

So you did this work. Good
You say you did the work and then you say they did the work. All I know is you have a problem with your car and also a problem trying to explain it.

 

you might want to start from scratch, replace the cat with a honda original, and the sensor with honda original. cost of parts may exceed cost of car's worth.

 

I thought I was pretty clear. They installed parts very poorly, I fixed what they messed up to the best of my ability. I made sure I stated what they did and what I did to get ahead of exhaust leak, old sensors or worn out cat suggestions. I'm a welder, not a mechanic. That's why I'm here looking for clarification as to why my code reader shows all good on readiness but is still showing a catalyst code when previously when I dealt with this p0420 bull, the readiness would flag the cat with a red X.