2002 GMC Yukon automatic door locks

Is this with the remote as well as the lock switch? When you are attempting unlock, and you hear the clicking, are the doors already unlocked. What happens if you manually lock them and then press unlock? If the work, try swapping the lock and unlock relays in the I/P fuse block, if they now lock, replace the one relay that is now in the unlock cavity.

The security lock flashing at unlock indicates the factory system is disarmed. An aftermarket alarm does present some other possibilities. Is it the factory keyless transmitters that you use, or the aftermarket ones? If the alarm has an integrated keyless feature, the system has to be tapped into so the alarm module can control the lock/unlock functions. There is no standard on aftermarket installations, it is at the discretion of the installer. Since you hear relays in the I/P fuse block when you activate locks, the vehicles keyless system sounds as though it's functional. With the fact that the aftermarket system is in place, normal vehicle architecture may be affected, and therefor factory information would be useless. The first approach that I take whenever aftermarket equipment is installed, is to remove the aftermarket equipment.