Hello ,
I want to describe something about my power lock in 2001 Lesabre .
I have a buttons on the two front doors , driver and passenger side .
when I push the button "Unlock" the doors are open but when I Push on "Lock" it not react , in both of them .
and now is the strange thing ... when I drive sometimes (specially when i turn RIGHT) the "Lock" work by itself ...

What could be the problem ? someone have the electric circuit of power lock system ?

So, the locks will not lock manually when pressing the button....

Do you have an RKE fob......will it lock with the key fob?

What about when you put the car in Drive, do the doors automatically lock?

As you can see, this is not a simple system like on other cars.....the door modules communicate via serial data......the easiest way to diagnose this is with a Tech II scan tool.....good possibility a "B" code is set.....sounds like a wiring problem to me......I doubt both switches went bad at the same time.....each door has it'* own module, and I doubt they failed at the same time.....so I think it is a wiring problem, rather than hardware.....was looking for something common to both sides, but since your power windows and mirrors don't seem to have a problem, it looks like the power and grounds to the modules are ok......

Like I said, a scan tool would show if the door module was receiving a signal from the door lock switch and if it was passing that signal on, via serial data, to the other door modules....but even I don't have a Tech II....

The doors locks from the remote and when i put the car in Drive .
the only thing that don't work is the Lock button . (the Unlock works fine) .
can you direct me where to looking for ?

Why do I have the feeling it may be the switch itself? Obviously removing the door panel for further testing would be best but...
Why not try spraying some electrical contact cleaner down in ( lock side) of the switch itself...
Water can get in there when window is down quite often, may be corroded.
Would the ground bus have anything to do with this?

i would guess something with the switch assembly. if it works with the remote most everything else has to work

But he says BOTH switches do the same thing.......if this happened at the SAME TIME, I doubt it is the switches failing at the same time......now if it happened where one failed, and then over a period of time, the other failed, then it could be both switches.....

Very easy to check the switch....we know the unlock works.....remove the switch, and ground the "C" terminal of either switch and see if the locks, lock...

I'll cheak it.
like I said ,sometime when i turn the steering wheel RIGHT the "Lock" suddenly works .
something very strange ... maybe i have a ghost in my car ?????

Ghost Locks Ha ha, Ya never know, stranger things have happened...
You could drive to the local cemetery after midnight, open all the doors, and ask Casper nicely, to go visit some of his other friends for a while....

Haaaa ....

Someone know where to start ?
where the device located ?