Did you try it from the grid home?
/u01/app/188.8.131.52/grid/bin/crs_stat | grep -i scan
Use the output to check individual services like:
You should have only one scan name that resolves via round robin dns to 3 ip addresses. If this is not correctly configured SCAn will not work properly for you
C:\Documents and Settings\>nslookup exa-scan.xxx.com
Addresses: 172.xx.xx.119, 172.xx.xx.121, 172.xx.xx.120