One problem related to dash wiring has been reported for the 1999 Toyota 4Runner. The most recently reported issues are listed below.
My vehicle: 1999 Toyota 4runner limited w/ port installed auto dimming mirror the + and - wire that goes to the auto dimming mirror were accidentally shorted almost causing a fire. Here's the problem as to why it's a fire hazard: it turns out that when the mirror was installed (either port option or dealer option on limited's and sr5's w/ sunroofs - not installed in japan), they just ran a wire (actually two - a ground and a "hot" wire mated together) down to the driver side kick panel and "hopped" the hot wire onto a hot lead of the power accessory circuit coming from the driver side door. This circuit is on a 30 amp slow-burn fuse. This creates a very dangerous situation if the wires to the mirror were to cross somehow - as they did for me. The fuse will not immediately blow and the wires can get hot enough to ignite the insulation or surrounding material before the slow-blow fuse will eventually break the circuit. This can take as long as 10 seconds depending on current and heat generated in the slow-burn fuse.