I read a great deal on various forums about people having issues with parasitic drain on their Lexus vehicles  What I did not read was very much useful info on how to diagnose the issue. Thus I thought, I would run the test on my 2015 LS460 SWB AWD. I started with a quality Multimeter that has both DC and AC current(AMP) measuring capacity. You put the black lead into the common port, and the Red lead into the 10A port, may also be labelled just AC/DC A on some meter. Having Alligator clips