Bzowk

Hey Guys -

About 3 months ago, my check engine light randomly came on on my 2003 GX470 which has 200,000+ miles. I own a bluetooth ODBII adapter so plugged it up and received the following:

P0420 - Powertrain
Catalyst System Effciency Below Threshold (Bank 1)
&
P0430 - Powertrain
Catalyst System Effciency Below Threshold (Bank 2)

I cleared it out and it reappears within a few miles. Sometimes just one of the codes, but eventually both. After much research, it seems this can be due to faulty O2 sensor(s), a cat converter, and/or leak in exaust system. I can't afford to take it in to get everything fixed so have a question.

Where should I start? I found that our Advanced Auto has Denso sensors for $61.99 which fit. My plan was to purchase one, install it, then if I still get codes, move the new one to the other sensor. If no go then, should I purchase a 2nd one or go straight for the cat converter?

What do you suggest? Thanks!

chiph9

Have you watched this?

3dreamer

Thank you! thank you! thank you!
I was on track to replace the CATs to rectify the P0420/P0430 code on my GX.
Battery Terminal cleaning, Air filter, MAF sensor clean and PCV valve cleaning seemed to do the trick. Didnt even have to replace spark plugs.