Look at your Fuseable links in the engine fuse block also. Mine blew but sometimes it would connect, then bounce off and on for a while causing a similar condition. Sometimes everything worked, sometimes it didn't. When it wasn't working the emergency flashers did work as well as headlights but not taillights or anything else.

Ultimate cause was hidden corrosion on/in the big clamp that holds batt. to body. It caused the 30 A fuseable link to blow several times before I figured it out.

'87 4Runner. '83 Honda XL250R. No mods on either.