[4Wheel]

You will be needing the schematic for your year, the Haynes books are worthless in the schematics for Toyotas.
First check the indicator light does the DF (defogger) indicator light come on? For this to happen the rear window limit switch has to be closed, (window in closed position), the fuses all have to be good and relay circuit wiring all good, so if you have a light that comes on this is great news.
The limit switch just enables the relay circuit and indicator light, keeps the DF from heating when the window is inside the tailgate.
If there is a light but it doesn't come on then debugg the circuit first.
this will be tough to do without schematics.

If you have an indicator light then next would be to inspect the two wires that directly connect to the DF in the tail gate, these tend to get warm and over time become brittle and break, easy to find and repair though. Just open the tailgate, take a screwdriver and force on of the door latches into it's "closed" position,(just pull the door latch to "reset" the latch to it's open position) with one or both of the latches "closed" the widow can be rolled out of the door BECARFULL!!! the widow will need support or it will break its mounting so use a couple of milk crates with a blanket on them.
Roll the window half way out, that will put the wires right where you can see them, the breaks are usually near the strian releif point where they are tied to the window frame. One side of the DF should have continuity to ground the other should be connected to the relay.

SO if you have light and main feed wires look good and one side of the DF is grounded then start in the front there is a relay on most Toy DF circuits with the ignition to the "run" position (without starting, you will need to hear) turn the DF switch on and off you should hear the relay clicking, if not the relay most likely is bad if it clicks check the color of the heavy wire connected to the back, you’ll want the one that does not have 12v on it when the relay is removed. Take a test light with a very sharp probe and push through the insulation on that wire if you get 12v toggling with the switch then the relay is good.

Now find that same color wire in the wire harness going inside the tailgate, sometimes the color codes change on the way that’s why you should work from schematics. There is only be one wire from the junction/relay block to the DF the other side of the DF is connected to ground through the wire harness to the chassis ground point.
Get schematics, good luck.