2004 Chevy Silverado - Door Lock Problems
 

I am having intermittent problems with a couple of my door locks:
1. My remote only unlocks the doors; it will not lock them. That may be a problem with the remote itself - I don't know.
2. When I put the vehicle in park, the doors should unlock. The rear driver and front passenger locks will intermittently not unlock.
3. With the driver-side door open and I press the lock button, delayed lock occurs. After shutting the door, waiting a few seconds, the doors should lock. Intermittently, the rear driver and front passenger locks will not lock.

Any idea what is causing this?

Thanks