I’ve had same problem, tried few times and it didn’t work, finally found post by Howard and tried one, and it did worked, now I’m having peace of mind, details below:
1. Turn the ignition on.
2. Press the door unlock button 3 times.
3. Turn the ignition off.
4. Press the door unlock button 3 times.
5. Turn the ignition on; the horn will sound.
6. Press the unlock button, then press the lock button. The horn will sound once if the autolock system has been deactivated or twice (one short, one long) if the system has been activated.
7. Turn the ignition off. The horn will sound once to confirm the procedure is complete.
Don’t worry if it wouldn’t work first time, try again, anyway it did worked for me. Hope it will works for you as well,
and this is what you need to do if you know 5 digit entry code, it is easier and quicker as well,
make sure the ignition is OFF and all vehicle doors and liftgate window are closed
1. Enter the 5 digit entry code.
2. Press and release the 3/4 control
while holding the 7/8 control.
3. Release the 7/8 control.
The horn will chirp once if autolock
was deactivated or twice (one short
and one long chirp) if autolock was
activated.