I've had a 3rd Gen for ~20 years but relatively new to this 2007 V8 4Runner SR5 with 175k miles on it.

Issue is every so often(couple times a month) it completely loses all electrical power, no lights(interior or exterior), not bell with key in ignition, tach and speedo drop to zero, engine dies and clock, radio and climate control reset. Deader than a doornail! This can happen when it's parked and I go to start it(hot or cold) or when I'm driving it, there just isn't a pattern. It has always started and restarted to date but I'm worried this won't always be the case. So far when I'm driving it at highway speed and everything dies it has restarted while moving but if I'm in city going slow it stops and I have to wait a minute or two and it'll restart no problem runs strong and no CEL codes.

I took it to an auto electrical shop and they couldn't find anything, has anyone had this issues with their 4th gen or can you point me in a direction to start the diagnosis? Thanks

im having a similar issue, i get random lights, so far i have swapped the alternator out, it seems to solve the problem so far. maybe its the voltage regulator that is going. your problem might just be a bad fuse, check the dome fuse.

Thanks @riceandpho I checked the fuses and everything looks good. How long ago did you replace your alternator and how often were you having issues before you replaced it?

I had an issue a while back where it would cut out while driving - turned out I was getting an electrical short when turning left with the steering wheel. Did the electrical shop recreate your issue?

I am also an old 3rd gen guy with a new to me 4th gen. Don't have any specific 4th gen experience to offer but I would start by removing the battery cable clamps, cleaning the terminals and reattaching the clamps. Then I would jiggle the ground cables to the frame and engine and the positive battery cable with the car running trying to reproduce the problem...also knock/tap on the battery. Then I would do voltage drop testing on the ground cables to the frame and the engine block (I would think the shop did all of this already). If nothing, I would replace the ground cables (or run add'l) going to the frame and the engine. You would think the shop would have removed and cleaned the contact points (which I would check before I replaced the cables) but the cables themselves might have a weak point that fails intermittently when flexed or with temperature or vibration that would not show up with voltage drop testing. You could approach the replacement as outlined in the old 3rd gen "Big 3 Wiring Upgrade". Another potential cause would be an intermittent internal short in the battery. If it is getting to the end of it's life, you might consider just replacing it.

Performing the "Big 3" Wiring Ugrade on a 3rd Gen T4R - A How To

mine was having issues for 3 weeks, cluster lights would come on, then 2 weeks ago the ac control does the random off to full blast to off again, then a few days after, the battery light turned on and off, im guessing its the alternator cause i swapped it out thursday last week and no problems so far. having it repaired in a next few weeks. hopefully the repair is not too much, these high output alternators went up in price, i paid 425 shipped to my door, now its listed as 420, so its a few bucks more.