So tonight I popped the underhood fusebox up and soldered the diode permanently into the wiring harness. No pictures in this post, but the essential info you need is - locate the huge right-hand connector (it's gray colored), and find pin B9 (second row from left, ninth cell down) and that is a black/white wire, this is the high-beam relay control wire; find pin D3 (fourth row from left, 3rd cell down) it's a pink/white wire and this is the low-beam relay control... install your diode between the two wires, with the stripe on the diode towards the high-beam wire. What I did in my own truck was to solder a 3" length of wire to each end of the diode and then cover the whole thing in a long piece of heat-shrink tubing, then use scotch-locks to piggy-back the diode to the two relay control wires.
Guys with HID high-beam headlights MUST do this mod or you might have the lights go out on you at freeway speeds.
Edited by Mr. P., 16 July 2009 - 09:49 PM.