Sometimes the 1989-1995 trucks come up as a Tacoma, depends on what vehicle database the information is being pulled from. If memory serves Discount calls my '91 a Tacoma.
It's possible for it to be a 2.4L 2RZ-FE but I think that would be a 2WD Tacoma as I think all 4wd Tacos got the 2.7L 3RZ-FE. It's easy to tell if we're talking about a 22R-E or 2RZ-FE. Which side is the exhaust on? Driver's it's a 22R, passenger's it's a 2RZ or 3RZ.
I suspect it's a 2RZ, if it's actually a 2.4L, because P0420 is an OBD-II code and the 22R-E never had an ECU with OBD-II.
Our recently sold Taco (with a 3.4L V6) threw this code right after I bought it and the dealer said it needed a catalytic converter, too. But one reason these trucks throw this code is by using 85 octane gas. I started using mid grade and it never threw the code again in the 10,000 miles we owned it.
BTW, we sold it through Craigslist for straight NADA if it gives you any direction as to real pricing. I had 4 serious look/inquires and 3 offers to buy.
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
"To live is to suffer, to survive is to find some meaning in the suffering." -- Friedrich Nietzsche