DOUBLE LOCK - Mechanically Decoupled
When the slider switches the circuit back to single lock it also pushes the double lock lever to the left until it stops. In this position, the double lock lever decouples the lock button from the latch mechanism. The lock button can be pulled but will not unlock the door since it is not coupled to the mechanism. Spring pressure pulls the button back down when released.
At this point, unlock is only possible when a key is turned to the unlock position from an outside door lock or if the GM receives the unlock signal from the EWS II control module.