I was reading the post because I have the same problem with a customers 4Runner. I was hoping the fix would be posted. It probably hasn't because it's probably not fixed like mine. Please post the fix if you do finally get that code to stay away. I need to know what to try next. I've about had it with this code.

 

If you check the wire at the ecu going to ks circuit and you show milivolts on your meter the ecu is the problem and seeing as how these ecu's are 20 plus years old it is most likely the problem. The capacitors on the ecu and the electrolytics go bad.the capacitor on the ecu is less than a dollar part replace it and all the other capacitors while your there and you sjould be good. Have not seen one yet that it didn't fix.