As RCAV8TOR said there should be a timer module in on the left side of the truck when your sat on it this has 6 male spade connectors on it check the wiring to it very carefully also these units do fail and if it has the contactor will not energize. The system works when the seat switch is made you energise the on demand switch on the steer column this switches on the timer if any one of theses isn't working the steering will not work. My bet would be the timer module though I've changed more than a few