In order to ping inside interface from an inside host or outside interface from an outside host, an access-list that is applied allows for the pass through of all the Internet Control Message Protocol (ICMP) traffic.
The access-lists that are applied on a specific interface allow or deny the traffic that passes through that interface.
On the other hand, the device must be configured in order to be able to respond to the ICMP requests that terminate on the Firewall Services Module (FWSM) interface and do not pass through the device.
In other words, in order to be able to ping a device that is located behind the FWSM, configure the appropriate access-lists on the appropriate interface. But, in order to be able to ping a specific interface on the firewall, configure the icmp command for that interface.