If you have owner's manuals for both vehicles, the FSS reset procedures are detailed there.

I will add that while following the instructions, make sure you perform the steps with the door(s) closed...not sure why it matters, but when I've done the same, it was never successful until I retried after I shut the drivers side door.

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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