Then try splicing the hub brown wires with a heavier wire leading to the coil mount or any good frame ground point. With a four tires off the ground check if you have awd. If you don't and don't want to replace the speedo,jump the brown/white wire from the speedo harness to another brown.This should at least give you awd. Remember too if the ecm isn't charging 14 volts at least back to the battery while running,this can affect voltage to the awd if the battery is being drained and awd may be erratic. I'd still check to make sure you're getting power to the speedo head also.There will be one red wire with constant 12 volts for memory and when the ignition switch is on,should have other wires power up. If they don't could be just a wiring short,if they do,then as you said the speedo may be shot. Plus you can't tell if the hall effect sensor is ok by looking at it. I've replaced plenty that looked good,but tested bad on the hall effect testing harness at the shop.