2006 DTS no crank. I replaced starter ran great for one day then no crank. I have been having trouble when turning off the car the ignition won't turn off all the way would have to re insert it into Park to remove ignition key. No error codes no security codes on dashboard could this be due to faulty ignition?

 

There are unfortunately many more possibilities to what could be wrong, but from what you are saying about having trouble getting the key out, I would first suspect an issue involving the shift cable or transmission. Watch the PRNDL when trying to start - you may be not fully engaged in Park and the car thinks you are in gear, so not letting you crank the engine.