I'm at a loss. So after everything I have spliced in a new 02 harness all the way back to the ECU. I have tested the plug and have 12v constant to one pin. The heater wire will switch to 12v. One pin is constant 4.5v. The earth/signal wire starts at 0v but I tested it at the ECU and it goes to 4.5v when the engine is running. It still is showing a flat line on the graph and throwing a p0134; Could the wires being melted together cause an ECU problem? Any help would be greatly appreciated.

 

you can easily figure that out by running on continuity check between the two leads. Any $20 multimeter will tell you.