passive restraint stuff.

I believe it has to do with the seatbelts. Do you have automatic seatbelts?

Unplug the harness and see what quits working.

Like miami and wntsom said, at least one of them (maybe both) is the seatbelt control. Holds the accelerometer and logic circuitry to lock the seatbelt from moving during hard stops. Probably also controls the body strap movement on automatic seatbelts when the doors open/close and when the car starts.

If I were you, I'd just rip the stuff out and go with it. I'd make no other changes. But then I would probably die in a fiery car crash. Second thought, you might want to research this a bit. No one likes a fire-damaged DSM. Or death.