YODAONE

Attached are images from 1999 Lexus LS400 wiring diagram manual depicting chassis ground points...

After all these years, it makes sense to remove the grounding point fastener and if corrosion, clean or replace...corrosion =resistance/voltage drop.



Ground point on right side engine bay uncovered when removing air filter box


Visible corrossion here
...and on the bolt...Will replace with OEM .

YODAONE

Lexus P.N. 90119-06390.
Ground point on drivers side inner fender well. The white tube in foreground is washer solvent fill tube. To access this bolt will require removal of battery. You will require a 10mm socket, swivel and long extension to work around this. 1/4" drive works best.

1/4" drive socket, awivelnand extension necessary to avoid disrupting plastic washer solvent tank fill tube

dicer

And it seems the only ground point is at the threads of the bolt and the body. Maybe also a good idea to run a thread cleaner or tap in the body nut as well to clean it. And personally I recommend either Vaseline or battery terminal protector on the threads to keep the corrosion from happening, as well as where the bolt contacts the wire lug or terminal.