Just purchased a very nice 2003 Silverado Ext Cab Z71. One owner , 68000 miles. Everything on this truck has worked flawlessly up to now. I have replaced the batteries in both units. The locking button on both units is working fine, it will lock the doors and set the alarm. The problem is with the unlock. One unit doesn't work at all, the other is working on a part time[whenever it feels like it] basis. This is the first vehicle I have ever had with this option, so I first read the owners manual, and then replaced the batteries. Is it that the buttons just wear out and you have to replace the unit, this does'nt make sense to me that the locking button is working fine on both unit's, it's the Unlock. Any help would be greatly appreciated.