2001 Mercury Sable

Computer problem
2001 Mercury Sable 4 cyl Two Wheel Drive Automatic 155000 miles

Great car! But the automatic locks are not working. They work fine with the remote. They do not engage when the car is put in drive. The lock error light is on all the time now. After depressing the 'lock' toggle inside to manually lock all doors, it will pop back to the unlock position all around. To lock all my doors I have to use the remote or depress all lock pins.
July 9, 2008.

IT is a pretty lengthy procedure to test this. A hand held diagnostic computer will likely be needed throught out this. I get the feeling that this may be realted to the GEM module, but testing needs to be done.