Got a 2008 Chrysler 300 with a 3.5 and high mileage. It runs good but has an intermittent miss and check engine light. I scanned it and the only fault code is an open circuit on the #5 injector. Wiring looks good and I replaced the injector pigtail, replaced plugs just because I was already there and cleared code. It lasted two days and it's back. What do I need to be looking for and how do I check?

swap injectors from another cylinder and see if the injector code changes cylinders also. You could go the local parts store and borrow or rent a noid check light.