How do you know if the speed sensor is out on a 1992 Toyota 4runner?

usually your speedometer, odometer, and trip doesn't work. It also may trigger check engine light with the O\D OFF blinking. I remember this happened to me . it went away when I turned it off. But came back when I hit Hwy speeds, usually and simultaneously when I let off the accelerator abruptly.

Order and replace Transmission Vehicle Speed Sensor.