There is a wire that goes from the center of the top of head/ block underneath the intakes, I was changing out the thermostat housing where I could see back in there , and noticed the jacket of this wire( actually 2 wires inside of the rubber shielding) was melted I am unable to find it , maybe someone knows where it grounds from? I know it grounds to top of head , then it goes to a connecting plug on the passenger side by fuel rail,!!??Any and all assistance greatly appreciated, Thanking everyone that finds time to help in advance.should also mention where it grounds to top of head it's a big ground lug, it's a bosch plug, with many numbers, tried googling to no evail.Lol, It's a 2001 ford ranger xlt , 4.0.thanks

 

You will get better help if you told us what you are working on, at least year and size of engine.

 

"Knock Sensor" for the V6~4.0L~SOHC;
basicly a microphone; without it you get the Family Truckster Effect !!!
Bolt to the top of EngineBlock in the "cave" under the IntakManifold behind the TStat Housing.
Plug to the electrical harness near right side of the IntakeManifoldThroat.