Refer to Checking the Maintenance Software section in this link
http://www.cisco.com/en/US/docs/security/fwsm/fwsm31/upgrade/guide/fwsm31up.html
Step 2 ..To boot the FWSM into the maintenance partition, enter the command for your operating system at the switch prompt:
â¢For Cisco IOS, enter the following command:
Router# hw-module module mod_num reset cf:1
â¢For Catalyst operating system software, enter the following command:
Console> (enable) reset mod_num cf:1
Jorge Rodriguez