Byte 0 is single locking, so when you approach the van, you only unlock the driver's door with the first press of the fob (prevents bad actors from opening other doors and stealing your stuff)
You say auto lock, but that is normally the locking of all doors as you drive away. Was that what you wanted, or did you mean the auto-lock that happens if you used the middle button to just unlock the rear door (that can lock again with your keys inside)?