I set up a Cisco ASAv 5525 and placed a Windows VM behind it. I created the NAT (PAT) policy and default route. The Cisco ASA could ping external IP addresses (eg 126.96.36.199). However, the VM behind that could not ping any external IP addresses despite being able to ping the Cisco ASA.
Windows VM: 192.168.2.200
Cisco ASA: 192.168.2.100
On the Cisco ASA use the following command
fixup protocol icmp