Module under passenger side floor board.

Red, black and black with white stripe from the looks of it.
Give me a bit and I’ll look at my 08 and see if I see the same connector on it.

Ok so I looked at both my smarts(08and 09) and haven’t seen a harness connector like that.
I’m willing to bet it’s part of a aftermarket alarm that disabled the car somehow.
If you can trace the wiring(if you feel up to) it may lead to a relay or something related to the alarm unit.
Smart only used the transponder key as a means of disabling the car from starting(even then it had to be a non programmed key or hot wiring the car that tripped it)
Snap pics of where it goes when you can it would be great.

I think that’s part of the passenger seat harness though.
Ain’t those sensors built into the alarm unit that’s under the car?

I’m going to look under my 08 when it’s not raining tomorrow and see if I can see a harness connector like that.(I would now but I just got done working on my 09 smart upgrading some on the suspension and I’m beat)
I can also snap a pic of the seat harness and of the harness that’s through the battery bin while I’m at it.
Seems odd that it’s not allow the car to start like that.

Seat sensor has three wires only and according to the service manual the wire colors are blue, red/yellow, blue/yellow.
The belt tensioner is three wires also and colors are black/red, brown/white and blue/white.
going to verify that tomorrow when it’s not raining.

Ok so I was a bit wrong on the wire colors but so far haven’t seen a harness connector like that so far in mine.
Going to look again tomorrow with the carpet removed and see if I see anything.

Hopefully the pics above help the op out.
The last pic shows the pigtail harness routed to the throttle pedal.