Left turning signal

Check for broken or weak body grounds.

My check engine light came on after a couple days of this happening. Ive also noticed that if you turn the key to on and turn on the left turn signal everything works but when you start the car it blips the radio the heat and also if you try rolling down the windows it goes in spurts. Other then the ground what could be causing this? They have changed the bcm before i purchased this van. It reset the miles on it from this change.