The door lock/unlock function from my driver's side door is not working to lock/unlock all the other locks on my 1992 300E. The passenger-side door and trunck lock do function properly to lock/unlock all the other locks, so the system that locks/unlocks doors universally is working. Just not when I turn the key on the driver's side door.

Is there an easy fix for this? I'm supposing it's got something to do with the driver's side door lock mechanism itself. Somehow, the signal from that lock isn't getting to the mechanism under the rear seat that controls the universal system.... electronic or mechanical issue?

Any help would be much appreciated. Thanks!!