Found this on TCCA...
Air Bag Diagnostic Codes
1989-1991
On the '89-91 systems, you simply count the flashes from the Airbag lamp to get the fault code.
Code Component Fault/Description
2 All Primary Crash Sensors Disconnected.
3 Air Bag Deployment Circuit - Low Battery Voltage or Low Backup Power Supply Voltage
4 Safing Sensor - Diagnostic Circuit Open or Low Primary Crash Sensor Resistance
5 Air Bag Circuit or Crash Sensor Circuit - Shorted to Ground
6 Driver-Side Air Bag Circuit - Open or High Resistance
7 Passenger-Side Air Bag Circuit - Open or High Resistance
8 Primary Crash Sensor - Not Mounted to Vehicle Properly
9 Primary Crash Sensor Circuit - Open or High Resistance
10 Diagnostic Monitor Internal Thermal Fuse - Open Due to Intermittent Short to Ground
1992-
In the 1992 model year the systems changed. 1992 System 2 was used in the Taurus/Sable, Town Car (built after 11/5/91), and Continental. To obtain the code on this system, count two sets of flashes and interpret it as a 2-digit code (e.g., flash-flash pause flash-flash-flash = 23)