I looked through the SR and SRC sections of the 2009 FSM and can't find any details on the "Occupant Classification System Seat Sensor Mat".
SRC-15 - SRC-17 shows what the different blinks mean.
SRC-17 tells how to clear errors once a malfunction is fixed - turn the car off and then back on.
SRC-157 (Wiring Diagram - SRS AIR BAG CONTROL SYSTEM)
Occupant Classification System Control Unit terminals 4 and 2 connect to Air Bag Diagnosis Sensor Unit terminals 1 and 26, respectively.
Terminals 4/1 through connector B201(Red)/M117(LG) pin 6.
Terminals 2/26 show no connector
Occupant Classification System Control Unit terminal 5 is ground through connector B202.