Cold starting problem Chevrolet Silverado 2

I'm having a problem with cold starts. The pickup is a 2008 Chevrolet Silverado 2500 with a 4.8L engine. In the mornings, it's hard to start; it often starts on the tenth try. It starts the first few times but idles at 400 RPM and then stalls. I've already replaced the temperature sensor with the original one, checked the fuel pressure (which is fine), and the scanner is showing something related to fuel trim. Also, sometimes when I start it, the vehicle starts and drives, but the ignition, oil, check engine, and battery lights don't come on. If I turn it off and on again, the vehicle returns to normal. I don't know if there's an ignition module involved...