There is an electrical plug under the seat for the motors. I recall that with the seat out and the ignition switch on, the SRS light would illuminate.

Have you tried a 10 mm ratchet wrench for the rear bolts? I'll bet the seat is right over the rear mount bolts.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles