Echo Catalytic code

[dutchs]

This problem is with a car that I am able to have for free if we can get the CEL out
and get it inspected. Thought we had it fixed last week, but another code
showed it's head. Here's the history:

The car is an 02, Auto, 4dr, with 265,000 mi. Was a daily driver for my
BIL for years, all highway miles. The car threw a couple codes within
the past year, and last month was up for annual NYS inspection. Dealer pulled codes and told them they needed an ECM, since another sensor
shorted out and ruined the ECM. I pulled codes, and found OCV codes,
along with random misfire. Replaced OCV, which had actually had it's wiring
harness broken off for a long time. Drove the car, and very soon the
CEL went off, so we made the appt for inspection (week wait) and of course the day
before the inspection, code P0420 comes up. Totally different code,
and no other codes present. I cleared them and gave it a couple days, and
back it comes. Tonight I followed some of manual's instructions, and put an
ohm-meter on the 2 sensors , before and after the catalytic, and both readings
were in spec, 14.6 front, and 14 rear, with range from 11-18 or so if I remember
right.
My questions is before we throw a converter in it, is it possible that with the engine
running so long with OCV and VVT-I not functioning properly, is the engine now running
differently and causing some confusion with the sensors? or did the lack of the OCV system possibly take out the catalytic converter? The car seems to run great, and has been
well maintained, tons of new wheel bearings/fuel brake lines/ etc.. and I think is a
viable vehicle for somebody to get to college/work for the time being.
Am I missing anything else? I see a test can done with the toyota scope, which
can actually read waves of the 2 sensors and compare them, is it worth having
a dealer (not the original one) do that test???
Thanks in advance,
Dutch

[the_unliked]

Got a similar problem, with my front and back sensors reading 12 and 14 respectively. Replaced my OCV for the same reason, which took care of most of my codes, but I still have the 0420. Just changed oil, plugs, filters and seafoamed.

Could it be a air leak in the exhaust line, or a loose wire or something? Please help us both.

[Stevo_Echohb05]

Check if you have a leak before the cat. ie. the front pipe donut

[dutchs]

I visually looked, but didn't notice what might have
been leaking there, don't hear a leak? wouldn't you
hear it if it was leaking there?

[dutchs]

did an intake treatment, and did notice some
exhaust leaking at the donut, small amount,
mostly at low rpms or idle, not much when
revved up. heading to get that checked out
at a muffler shop, think we are looking at a
new cat , any recommendations on which one
to buy? (walker, catco, bosal?)
thanks again