Cisco PIX 501 is one of my favorite hardware firewalls to work with. I have couple of them and I am still using these (2011). Most of the time ICMP is disabled on these devices. To enable the ICMP please logon on the console or use SSH connection and run the following commands.
pixfirewall# conf t pixfirewall(config)# access-list ping_acl permit icmp any any pixfirewall(config)# access-group ping_acl in interface outside pixfirewall(config)# wr mem
That’s all. I was not easy to configure this through PDM and I like using the console more. Ping and tracert to google.com work fine now.