Refer to this to troubleshoot your problem.
http://www.veryuseful.com/mustang/tech/airBag/airBag95.html
The air bag diagnostic monitor measures the voltage at Pin 14 of the air bag diagnostic monitor connector. Voltage at Pin 14 should be equal to battery voltage. If the voltage at Pin 14 drops to less than 8 volts, the air bag diagnostic monitor will flash out on the air bag indicator a DTC 12. If the voltage at Pin 14 drops to less than 5 volts, the DTC 12 will also be stored in memory. Should the loss of battery voltage at Pin 14 be intermittent or repaired, the air bag diagnostic monitor will flash out a DTC 52 (or higher priority code if one exists) on the next ignition switch cycle.
Low voltage at air bag diagnostic monitor Pin 14 can be caused by:
- An open in the battery circuit that would prevent battery voltage from reaching air bag diagnostic monitor Pin 14.
- A short to ground on the battery feed circuit between the fuse and Pin 13 or Pin 14 of the air bag diagnostic monitor.
- A concern in the charging system causing battery voltage to drop below 8 volts.
Unplugging the module probably won't hurt anything though according to the above, you'd be best off probing for voltage at the appropriate pins to see exactly what's going on. If your battery is almost dead, stop turning it over until you charge it or you'll have to keep investing in fuses.