I have an '02 4wheel-drive, sr5 with almost 200k on it. I went to the beach for a camping trip this weekend and while crossing a rut in the sand i heard a couple beeps and all three lights apear. Luckely i had my code reader with me and I pulled a po420 and po420-pd code. (This says catalyst eff. below threshold; bank 1). After researching this i've heard that the catalytic converter could be stopped up or even just ready to be replaced. My local shade tree mechanic told me to run some sea foam through a tank of gas. He says he's had a lot of luck with this. I'm also going to try to just clear the code's and disconect the battery cable for a little while and see if it goes away.

Does anyone have any input or advice for this situation. I'm a college student that does'nt have mommy and daddy to fix things for me and looking at fixing this the cheapest but most effecient way possible.

Thanks for any and all help.

The FSM says the first step is to test the front O2 sensor (or A/F in your case...I think). It's a common code and it's usually that sensor. If it's never been replaced, I would just do it. Here's some good food for thought:
4x4Wire - Tech: Time to Replace the O2 Sensor on your 3rd Gen Toyota?

Yotatech has more info than you know what to do with on this issue also.

Ya i had the same codes last summer and it it turned out to be my A/F sensor I have a 2002 as well but it only had 88k at the time so I would be impressed if your A/F sensor lasted 200k

I just ran a tank of the sea foam through the 4 runner and used the scanner to clear the codes and as of now ( 50 miles later) the lights have not came back. KNOCK ON WOOD. Thanks for all the info guys