2003 gmc envoy_slt
:tiphat Welcome :tiphat . Try resetting the security setting. I don't know how it was lost. Try to start the truck. If it won't start and the security light is on, leave the key in the ON/RUN position (not the ACC or OFF position). Leave the key in the ON/RUN position for at least eleven minutes. The light should go out. Turn the key to the OFF position for at least thirty seconds. You may have to do this more than once so turn all accessories and lights off. Repeat the precess until it starts.