Be careful out there with your 2006 Buick Lucerne. The rear door locking mechanism is cheap and poorly designed. Our rear left passenger door would not open, either from the inside or outside, even when the door was unlocked. My wife delayed letting me know about it for a few days and then on Friday she had passengers in the rear seat expecting for them to be able to get out of the right read door. Nope. It too now would not open and the passengers had to climb out over the seats and exit the front doors. Have seen this reported on some of the Buick sites, so it is a general problem with the Buick Lucerne. It is a safety issue. Do not allow passengers in the rear seats. If you get in an accident, and the rear doors cannot be opened, there may be deaths. It cost me nearly $1000 to have the doors fixed. Wrote GM and they did nothing.

This has been an on going problem since 2007-8, it wasn't covered under warranty, but the dealer released the latch by flicking door handle and hitting door near latch right rear, he said it was only 2006 Lucernes right rear doors and to keep it oiled and change lock.I didn't have much faith in changing lock because why didn't they do this while the car was under warranty?

So I kept it oiled, it happened again, I fixed it and oiled and it happened again. This year the right rear and then the left rear door 30 mins later? If it was a known problem why weren't the locks recalled and changed. I am still trying to open my back doors but the old method is not working!!!! When I get them open????? I will oil them weekly I suppose.