You should start a new thread to catch the interest of folks who really know the W140. The W126 factory alarm is much simpler than the W140 factory security system. The W126 alarm is just that - it doesn't disable anything, just makes noise and flashes lights. It won't hinder anyone's attempts to start the engine and drive away.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD