So heading home from work this morning I had a second or two where it seemed like I lost all power to anything inside. The radio went silent, display and dash all turned off, I expected the engine to die next. Luckily I was able to make the 7 minute drive home without any further issues. Not sure if it is related, but when I parked I noticed my drivers side headlight was out. I played with turning it on and off and it seems to be a bit flaky, sometimes working sometimes not. I would assume that if something was wrong with the headlight wiring or ballast, it would blow the fuse before shorting and dropping the voltage low enough to shut off my dash and whatnot. I am about to go to sleep, I will check fuses and whatnot when I get up. Has anyone had this happen before?

 

The alternator might be on it way out. You might want to check the alternator. I had the exact problem with my son's 06 4runner. I replaced the alternator and the new battery. The problem went away. It has been couple months trouble free now.

 

2nd post may have a point. The ECU and lights will run down to about ~10.5 volts or so (HID), some of the modules inside are controlled by a power management computer and I saw this happen when draining the battery futzing with Techstream, a bunch of stuff inside dropped off.

Check the Alt and Battery!
How's it been treating you otherwise? Still tinkering?