I had it when my ML was new, but was later told that the option wasn't really supposed to be enabled on the 99 MLs. All sorts of reports of unintended locking occurred (leave ML running at car wash, close doors, locks engage, etc.).

Unintentional locking occured twice for me...once at home, and the other at the service entrance at the dealership. They had disabled it since then.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car