bb2tosc

Hello

I recently bought a 98 SC400 and its been great so far.
When I bought it it had the check engine on, which turned out to be the pre-cat O2 sensors which I replaced both.

The light went out for a day or two and came back on. Now its throwing code P0420 (reduced catalyst efficiency, bank 1)

I did some search here and on the internet but couldn't find a definitive conclusion about it being the cat or the O2 sensor.

I'm leaning towards bad cat because they make a lot of noise when I shut the car off. Its a clicking sound most of you have probably heard but I think in my car is a little too much noise.
Even in 10 minutes short drives it will make the clicking noise once I shot it down.

Any tips from someone who has had this problem before? Any way to find out if in fact my catalytic converter is bad?
Would a muffler shop be able to weld a aftermarket one like magnaflow in its place or does it have to me OEM?

Thanks for the help

Dexter72

Since most codes are universal now between all manufacturers, P0420 is usually a cat converter code.. See if some other members or posts show what they used, for an aftermarket cat converter.. Much cheaper than factory, hopefully a good aftermarket part.

3L4jzz31

iTrader: (2)

Good info in this thread. It gives tips on what to look for in voltage on the o2 sensor before you replace the cat, as well as a discussion on this exact issue with high flow cats instead of oem.

https://www.clublexus.com/forums/per...er-cat-o2.html

If you end up concluding (or replacing everything) and the issue is not the o2 sensor or cat. Then the fun begins