2007 Cadillac Dts crank start then dies

2007 Cadillac Dts will crank over and start then dies immediately. Had a code p1682 for ignition switch. Changed that and still getting the same results. Going to code agian since putting ignition switch on to further diagnose. Was maybe thinking crank shaft sensor or cam and wanted to know the location of both and what would cause a crank start then stall symptoms