Mod of the North.
Join Date: Mar 2011
Location: Take a wild guess...
Usually in the tail section. I am not sure about the 99 but on my 2010 it slipped over a post in the center back of the tail but my battery was mounted forward of where yours is. For you I would check the middle pic to the left of the battery near the positive terminal. I am guessing that block is the ignition relay? Should be a bracket about a half inch wide and 3/4" tall sticking up close to there. the sensor will slip over that.
Alternatively, the harness will pretty much lead you to the right spot as the wires will naturally fit best leading to the OEM mounting point.
Favorite Quote: "Told y'all I was gonna blow shit up." -Fubar
Total MPG Wins: 189 (Retired)