OK Here goes. 99 4Runner with 192600 miles. This truck is still in great shape & runs good with no other problems. Check engine light came on. Took to dealer to get checked.( reason for this is another story ) Came back with code p0420 & need to replace both cats at a cost of $3410. Didn't want to spend that so decided to go with the URD simulator. Unhooked battery installed simulator then drove 35 miles. These were 3 short trips & then the check engine light came back on. Any help with this problem is greatly appreciated.

 

First off, buying new cats at the dealer is probably the most expensive way to do it. Doing it elsewhere could be a lot cheaper, doing it yourself will certainly be a lot cheaper.

And it might not be the cat, could be the sensors. Or some other reason, and the reading at the second O2 sensor is just the symptom.

http://www.easterncatalytic.com/educ...he-po42o-code/

 

try resetting it and see what happens. i'd look into the torque app (if you have an android phone) and the elm 327 bluetooth obd2 adapter. that may save you some troubles in the future. you can even read the rear O2 sensor (bank 1 sensor 2) voltage using that app, but not the front voltage (bank 1 sensor 1).

i just went through this P0420 code myself and did the cheap radio shack fix and gutted my cats. threw a code 2 days after i gutted the cats, reset the code, and it hasnt popped back up in over 130 miles

 

maachine THANKS!!

Reset & have 345 miles on with no light. Just wondering if the cats should be taken off & gutted. Will they completely clog or are they just out of elements to work right. This is the wife's truck that she does not want to part with so I don't drive it very often. Just go by what I'm told as far as needed repairs.

 

Get two new cats from Rock Auto and do it right.

It might have only been the rear sensor.