Exacheck is usually installed by default under:
/opt/oracle.SupportTools/exachk
Before being able to upgrade exacheck you need to obtain the newest release from Oracle Support. It can be found via Doc ID: 1070954.1
The downloaded fil must be placed either on the same location on all nodes in the cluster OR on a shared location accessible from all nodes in the cluster.
In this case the downloaded file will be placed on:
/shared/tools/exachk/latest
To do the actual upgrade of an old version of exacheck use the follow commands:
export RAT_UPGRADE_LOC=/shared/tools/exachk/latest
/opt/oracle.SupportTools/exachk/exachk -upgrade
You should be seeing output similar to this:
.... to come...