Well, I think it is the temperature sensor wire. I looked under the street side near the front, right under where the plastic tube goes into the wall above, and the same type plastic tube comes through the belly pan and curves back toward the rear for about 6 inches and it is clamped to the belly pan. The end of the plastic tube is open and I cannot see any wire in it. Looks similar to a drain tube.
Here is an interesting and a scary thing about this wire that has happened TWICE!
When I first paid attention to this plastic tube, shield and wire, I pulled the tube out of the wall and slid the shielded wire out of it and was thinking of just cutting the copper wire and shield off flush with the wall, since it seemed to have no useful purpose. Then the shielded wire touched the aluminum frame around the compartment door and electrical sparks
occurred, like there was 12 volts on the shield and wire!! I carefully put the shielded wire back in the plastic tube and pushed the tube back in the wall as far as it would go. I then measured the voltage on the shield and wire to the metal frame and got ZERO voltage. I then touched the wire to the metal frame and NO sparks. I thought, Hmmm, what was that all about! I then left it alone and thought "I need to find out what that wire is for".
Today, the same thing happened, I pulled on the wire and it would not come out of the tube. I removed the upper part of the tube from the wall and was about to cut the shielded wire and SPARKS occurred as it touched the metal frame. I went through the same procedure as described above, and no voltage on the wire. VERY STRANGE. All I can figure is that when I remove the plastic tube, the wire comes in contact with a bare hot 12 volt
line in the wall somehow. When I put the plastic tube back on the wire and push it back in the wall, it breaks the connection! I know this sounds a bit far-fetched. I was wondering if I removed the clamps on the 6 inch part of the plastic tube on the belly pan, if I could then just pull the tube and wire out from the bottom? I cannot see the wire in the tube from the bottom part of the plastic tube on the belly pan. Is the temperature sensor small enough to fit inside this plastic tube that has about 1/2 in inside diameter? I have decided I need to get this thing out of there, somehow. I do not want any SHORTED 12 lines! Bill