Detach the CRS ORACLE_HOME from Installer repository
$ ./runInstaller  -detachHome ORACLE_HOME="/u01/app/11203/grid"
Starting Oracle Universal Installer...
Checking swap space: must be greater than 500 MB.   Actual 6151 MB    Passed
The inventory pointer is located at /etc/oraInst.loc
The inventory is located at /u01/app/oraInventory

Verify 
$ $ORACLE_HOME/OPatch/opatch lsinventory -all   
Oracle Interim Patch Installer version 11.2.0.3.4
Copyright (c) 2012, Oracle Corporation.  All rights reserved.
Oracle Home       : /u01/app/11203/grid
Central Inventory : /u01/app/oraInventory
   from           : /u01/app/11203/grid/oraInst.loc
OPatch version    : 11.2.0.3.4
OUI version       : 11.2.0.3.0
Log file location : /u01/app/11203/grid/cfgtoollogs/opatch/opatch2013-08-13_13-00-03PM_1.log
List of Homes on this system:
Inventory load failed... OPatch cannot load inventory for the given Oracle Home.
Possible causes are:
   Oracle Home dir. path does not exist in Central Inventory
   Oracle Home is a symbolic link
   Oracle Home inventory is corrupted
LsInventorySession failed: OracleHomeInventory gets null oracleHomeInfo
OPatch failed with error code 73

Delete unused entries from /etc/oratab and remove ORACLE_HOME files at OS level
#  rm -rf /u01/app/11203/grid

Reference:
How to Deinstall Oracle Clusterware Home Manually (Doc ID 1364419.1)