Well I had a code 21, O2 sensor short or open. So I call my buddy at the Toyota dealer and ask him to pick me up a new O2 sensor. He gets it for me at his price $83 brand new, NICE !! So yesterday I hit the nuts with PB Blaster and take out old O2 sensor and put in the new one, easy fix yeah right. I reconnect the battery and start the truck, Check engine light still on. So I pull the code and the same thing Code 21. So I pull the fuse to the ECU and same thing. I climb back under the truck and start to look around, and found the wire harness that runs under exhaust pipe melted. The pipe had hit the fiberglass wrap and melted the wires. So spliced the broken wires, wraped everything back up with electrical tape. And low and behold no more CEL. Nice when things come together.