Toyota tacoma 96 OBD2 trouble code

I got a a trouble code of PO 420 which I can find in my chiltons book no problem there. The issue is I work on systems on tugboats and first thing you do is clear it and see if it comes up again. I did that on my truck and now I am worried that i cleared it and now it wont come up. If it is an actual issue should it come back up if cleared?

Yes, it will come back if the condition that created to start with is still present. I would not worry about it, but I would take a good look at my O2 sensors (at least inspect wiring) and check for exhaust leaks. Other than that I’d tool along happily until the dreaded light returns.