Hi,
Seems to me that the internal host is probably trying to connect to some remote host and the ASA receives a Type 3 Code 3 ICMP error message that tells that the remote host in unreachable or the destination port was not listening/replying to a connection attempt.
Does the output of "show run policy-map" show a "inspect icmp error" configuration under it? To my understanding it not enabled by default. Also "inspect icmp" is not enabled by default.
But as I said, to my understanding the message tells us that the ASA can not see a matching connection to which this ICMP Error message corresponds to. It might be because missing the "inspect icmp error". I am not really sure. The actual ICMP error message incoming seems to suggest that your internal host(s) are trying to connect to some remote host that is not accepting the connections or just is not listening on that port.
- Jouni