Hey guys, I know this is an old thread but maybe y'all might see this. I just now had the same problem.
My 89 FJ62 ran for 3+hours just fine, got home and went to park--- boom, it just shut down completely. No electrical, lights, no nothing. I was in reverse, powering down pass window and it just went dark. It's about 14deg outside, not sure if that matters and window could be coincidence, never had issues with it before. Tomorrow when it gets up to a toasty 20degrees I'll check battery / alt wiring, but any suggestions before I go out would be very welcome.
Also.... what issues with EFI wiring could be problem?