2004 Hummer H2 Starting

All was well but came out to find it 'starts' every time but quits withing 2 seconds. Fuel was low but after adding 5 gallons getting the same. From reading, acts like 'passlock' screwing up. Found no tampering. Fuel problem maybe but kicks off and sounds fine for two seconds... every time. If you have the 'passlock' workaround or other ideas.... Also disconnected the battery once to reset anything ....

Thanks, T