Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
It sounds to me as though there is a faulty part. Let me look at that wiring diagram a second to see where all these circuits meets or what they have in common, cause that may be where the short is.
I need to know which express this is and what engine?
I see the G302 ground behind the left kick panel is a common ground for the headlamp/dimmer switch, the turn signal hazard flasher module, the body control module and the courtesy lamp relay, so I would unbolt that ground, clean the metal with sandpaper and reattach the ground and then check out the lights now.