DTC codes P0420 and P0430 appeared the same day

Thanks for your reply.

The catalytic converter(s?) are built into the exhaust manifold. There was a change to the design around 2002 from the easier to replace inline cat on the previous models of RAV4. The reason think/thought there were two cats is:

1. Here's a link to a webpage from OReilly's auto parts showing a picture of the combined exhaust manifold and catalytic converter part that will fit this car.

http://www.oreillyauto.com/site/c/detail/DOE0/674593/07099.oap?year=2002&make=Toyota&model=RAV4&vi=1388910&ck=Search_catalytic+converter_1388910_-1&keyword=catalytic+converter

I attached the photo from the webpage with this reply.

2. The DTC of P0420 and P0430 which both showed up, are listed as left and right banks of the catalytic converter.

3.There are two sets of upstream and downstream O2 sensors, one for each of the "banks" referred to by the DTC codes which are shown in the photo of the part.

I turned off the "check engine" light and I am seeing what happens.

My wife took the car out for the short trip (1.5 miles then parked to shop, 1.5 miles back) and the light didn't come back on. I'm taking the car out this morning for a trip that will have 4 legs of over 30 miles each with 1/2 to 1 hour stops in between each leg of the trip. When I get back I'll see what info I can get from the software I have (EasyOBDII) running on my laptop with my wife driving the car, and I'll examine the spark plugs and the MAF sensor. Then I'll get back to you....

The car actually has 180,000 miles on it, not the 160,000 miles I thought. (I hardly ever drive it: its my wife's car).

After clearing the codes, I did a few things. The iridium spark plugs had 90,000 miles on them so I replaced them. I cleaned the MAF sensor. Then I then went on a trip where the engine fully warmed up and cooled four times. No diagnostic codes showed up.

I tried to see what the O2 sensors were doing while the car was operating. My software can only see live data from the downstream O2 sensors. The left side (bank 1) sensor is original equipment (180,000 mi), and the right side (bank 2) sensor has 90,000 miles on it. The left side (older) sensor fluctuated over a wider range of voltage more rapidly than the right side. The MAF seemed to working OK in that it was reporting low values when the engine was idling and high values when the engine was working hard. Fuel trim values were small. Long term 2 - 3% short term 1 - 7%. I was using an old ELM27 device plugged into a laptop with EasyOBII software that seemed to update very slowly. I'm going to get a more modern scan tool.

I'm thinking of replacing both of these downstream O2 sensors, especially the one with 180,000 miles on it. I'm wondering about the upstream A/F sensors. One is two years old ( 25,000 mi), and the other is five years old ( 70,000 mi).

Otherwise I suppose I'll wait and see. Why did the P0420 and P0430 codes show up then disappear? Is there anything else to do to try to extend the life of the catalytic converter?

After I replaced the two downstream O2 sensors and the upstream sensor that had the most miles on it, and the spark plugs, all symptoms went away. The car now starts without a puff of black smoke coming out the tailpipe, and the check engine light stays off. Its been more than 1,000 miles and all is well.

Your diagnosis that the catalytic converter was bad seems incorrect.