so starting a new thread based on comments from previous thread here that started out initially with a long standing p0420 code
https://www.chevyhhr.net/forums/prob...-cat-o2-66077/

back in feb/march i changed the converter and O2 sensors - the upline sensor to a NTK initially. Couldn't get off the original o2 sensor (this is a 2006) and simply unplugged it for the time being and put the new sensor on the opening on the new cat.
after these repairs, the p0420 code went away but p0132, 0134 and 0135 came up. Determined the NTK was defective and bought another brand and installed that in place. 132,134,135 went away but then 420 comes back.
old sensor is still in original position as i haven't had a chance to buy a different type of socket that will fit.

Also i changed out the apparently defective NTK upline o2 sensor for some cheap brand off amz. This caused the p0132 and p0134 codes to go away.

here's a brief timeline of what has been done recently

march ?? new catalytic converter installed along with o2 sensors.

april 3
I changed the fuel pump to a delphi brand pump - cleaned the gas tank - there was a LOT of charcoal bits in there
I also changed the evap canister and evap valve/solenoid parts
at this time i still had confirmed 0134 and 0135 codes

april 5 0132 code comes back too

april 16 p0442 code makes brief appearance

april 17
cleared codes after installing replacing the NTK o2 sensor with another new upline o2 sensor (different brand)
now back to starting board as p0420 code comes back

april 26 p0455 code also joins in with po420 code - - before it happened i had a 'check gas cap' msg come up the day before. cap is only a few years old.

so i am really frustrated at this point. Could the new cat now ruined too? I was driving 400-500 miles with the apparently defective NTK upline o2 sensor - can this be THE cause or just ONE possible cause?
I read in another post about heavy metals being bad for the HHR converters when using high mileage type oils.
what's up with the EVAP errors now that have showed up after1000 miles of driving since all these repairs? the evap box and other smaller part seemed pretty basic with only a few easy hose connections.

if i didn't need the vehicle so much i'd be tempted to take it out back and put it down like a lame horse. (dealing with an inoperable cooling fan and no a/c at this time)

 

Do you have a link or manufacturer and model number for the new cat?

The cat/downpipe I got from ZZP passed emissions right after installation, but sometime between then and the next test 2 years later,it crapped out. I didn't get a P0420 from it, but the Catalyst test for emissions testing readiness, just would not complete. The original that I thought was surely bad, after lots of oil burning, turned out to be good.

 

Here’s the one i bought

https://www.ebay.com/itm/203094215300

i took my original to the recycling center where a guy gave me $50 for the old one offsite after overhearing all the hoops i would have to jump through for the recycling center to take it as a cat and not basic scrap

 

At least they have a satisfaction guarantee.

 

$100 cat won't last. Get one that meets carb standards.

 

You get what you pay for. You paid for a cat that would pass for a long enough period for you to sell the vehicle to someone else.

 

The link you provide shows there were 2 bung plugs provided. What happened to them?
They are provided for exactly your circumstance, the #1 sensor on the manifold.
If they didn't come with ask the vendor to provide them.