My '03 1500HD, has a condition where both rear doors will not lock by the drivers power lock button or the key fob. If I manually slide the lock buttons, to the locked position, then I am able to power unlock the rears, using the key fob or drivers button. I am thinking that the rear power door lock solenoids are weak. Are there any other tricks, or obvious diagnostics, before I yank the door pannels?

 

there is a "rear unlock relay" in your panel fuse box..try wiggling that