Another PO420 thread

I have a 2001 Tacoma SR5 2.7 with 210,000 miles. Some background...have had the CEL on for several years, when it first came on i got it checked 1135 & 0125. Upstream O2 sensor and a thermostat. I finally got those 2 problems fixed. Replaced w/ a OE denso O2 sensor.
Drove about 50 miles when I got another CEL...this time 0420. After searching these forums, Im still not sure if it is a cat problem or the downstream O2 sensor. The exhaust system has been worked on recently, so I dont think it is a leaky exhaust. I work night shift so I will check underneath on my way to work to see if the cat is glowing red!
Until recently I only lost 1 or 2 MPG with the CEL being on and about two weeks ago I noticed a loss in power and even less MPG.
After replacing stat an O2 sensor, I've still got power loss and piss poor MPG's......
Any suggestions or advice would be helpful! Thanks!

 

checked last night- no glowing cats or any kind of rattle in them.
so my question is... where do i start? downsteam o2 or get the cats replaced?

 

i just asked the same question i took it to the shop he said the cat was bad and i myswell change the o2 sensors also not sure if you have a v6 or not but i think the v6 has 2 cats so you might have to replace both.

 

same problem here, keebler. Mpg loss is annoying

 

i guess i will replace the downstream sensor and go from there

 

Clean you MAF Sensor thats what my problem was

 

I will try that and see what happens....doesnt seem to hard to clean the MAF sensor! Thanks