I hava 2010 gmc terrain no start or crank

What is your question?

I replaced alternator and starter bad alternator took post off battery to replace parts put post on jump truck and tried to start nothing took post off charge battery put post on tried to start as soon as i turn key the check engine light flickering and throttle clicking at same time i tried taking post off and back on no blown fuses or relays but i changed out starter relay ecm fuses pretty much all relays and fuses plug up scanner no codes but this odd one P15A1

What makes this problem better or worse?

Don't know

How long has your 2010 GMC Terrain had this problem?

Couple days