Well just like it says where does it go? Can't find it...just got done doing head gaskets and can't seem to find any open plugs that it can reach to?

 

It's a yellow wire with a green line and gray with a red line goes into another plug with the same wires coming out the bank of the plug then into the big group of wires that run along the drivers side valve cover

 

A/C plug ?

 

Ac is on the other side and this won't come near any ac lines or compresor

 

For the 4.2L it's:
(On left side of engine) Cylinder Head Temperature Sensor
Grey / Red
Yellow / Light Green

For the 4.6L it's:
(Top Front of Engine) Cylinder Head Temperature Sensor
Grey / Red
Yellow / Light Green

 

Here is the component locator guide from my service manual. Won't let me load. If you need it, PM me your email address and I'll send it to you.

 

Nope no need for it.figured it out...it was tucked on the inside of the left head under the intake...thanks for saying it was the head temp sensor! Couldn't find any wiring diagrams that said wire colors combos to what it's for where did you get that?