2001 Oldsmobile Bravada check engine light on won't pass in

my mechanic has had the car for over a week and can't get the sensors to reset. when he plugs it into his tester it comes up secondary evac system failure. he was told by a mechanic that if he drives it 250+ miles the sensors should reset and it should be able to pass inspection but as of yet we have had no luck in getting them to reset this way. when we asked if I brought it into the dealer if they had a way of reseting the sensors he was told they normally tell the customer to continue driving it until the check engine light goes off and then bring it in. the check engine light seems to go off and come on with no change. Does the dealer have any way of reseting these sensors or do they really just tell the customer to just keep driving it. I only have a 60 day temporary pass to drive the vehicle uninspected and its already pass the time. Any help would be appreciated.