Chevrolet Repair: Key ignition, theft deterrent system, turning the key

Question
I changed my ignition but now it starts but shuts off right after a few seconds.  Chev truck2004 2500hd silver ado what do I do?

Answer
HI JOHN,YOUR TRUCK HAS A THEFT DETERRENT SYSTEM..I WOULD SUGGEST TURNING THE KEY ON AND LEAVE IT IN THE ON POSITION WITHOUT TRYING TO START THE TRUCK FOR 30 MINUTES..MAKE SURE BATTERY IS STRONG ENOUGH TO HANDLE THE LOAD,IF NOT PUT A CHARGER ON IT.TURN THE KEY OFF AFTER 30 MIN AND RETRY IT AGAIN. THIS MAY RELEARN THE THEFT SYSTEM. THERE ARE A FEW WAYS TO RELEARN THIS SYSTEM BUT THIS IS THE MOST COMMON WAY...IF THIS DOES NOT DO IT,GOOGLE YOUR TRUCK FOR THE CORRECT PROCEDURE,YOU SHOULD FIND IT THERE. IF YOU ARE NOT ABLE TO GET IT RUNNING GET BACK TO ME AND WHEN IAM AT WORK MONDAY I WILL LOOK UP THE CORRECT PROCEDURE FOR YOUR TRUCK,,I WILL NEED THE LAST 8 OF YOUR VIN#..IF THIS TAKES CARE OF IT WOULD YOU PLEASE RATE MY ANSWER. THANK YOU, TOM