Its a test for parasitic draw. You disconnect the neg lead and hook your test light between the ground cable and neg terminal. When u first hook the light up it will illuminate. As the capacitors in the control units bleed off it should go out. IE: when your dome light fades the test light should go out. You can also do this with an ammeter hooked in series, after the car goes to "sleep" there should be less than .5A drain on the battery. Pulling the various fuses one at a time isolates the circuit that you need to invesagate further. Usually a drain is caused by a failed component. You have something staying on tha ahouldnt be. I've seen things as simple as a bad seat motor, to things as annoying as a bad ecu causing parasitic draws.
......And just as they're about to catch me.....Twin......Turbos......Kick.......In!
