Nothing new but.....I just bought this 04 4runner 4.0L on Friday and it has thrown these codes already!!!! Bought it from a used dealer. Says they have 30day 1500 mile drivetrain warranty. 115k miles. Mint truck always serviced at dealer on carfax. The dealer admitted to me they got it with the check light on and it needed a cat which they relpace bank 2 rear cat (drivers side). It has 4 cats total. Researching more seems like the front 2 cats are likely the culprit. Any Toy techs out there shine some light for me. I do have a scanner that has realtime readings if that helps. I am so pissed about this issue right now. I just sold my 04 BMW X5 thinking it would give me troubles to get this....wtf...thanks in advance for the help.. Scott

 

Those codes are for catalyst efficiency. If your scan tool shows live data you need to watch A/F sensors bank 1 sensor 1 and bank 2 sensor compared to the o2 sensors bank 1 sensor 2 and bank 2 sensor 2. the cats in question are built into the manifolds. The A/F sensors are before the cat and the ecm use them to read the fuel ratio from the engine. While the o2 sensors are after cat and measure the ratio coming from the cat. While looking at the live data For normal operation the A/F sensor should move up and down around 8 times every 10 seconds. The o2 sensors should stay pretty much the same. if there is a cat issue the o2 sensors will go up and down just live the A/F sensors. This way easier to see if your scan tool has graphing.

 

Seems like you could be freinds with lots of peeps on here..
Keep up the good work.