The wiring diagram shows a sequencing module. What is this and where is it located?

 

If you're talking about the seatbelt interlock sequence module, I believe it's behind the bulkhead/carpet in the rear compartment on the driver's side.

This is the gem that makes sure you 1) sit down, 2) buckle your seat belt, 3) your passenger is buckled, before you 4) start your car.

Your car probably has this disconnected.