I have not tried this procedure I ussually recommend rebooting server

Adding a LUN To add a new LUN to an existing PowerPath configuration:

1. Ordered List ItemScan the bus for the LUNs.
2. Ensure that the new LUN is created on the storage side and recognized by Linux.

  On SLES 10 SP4 , SLES 11 SP2, SLES 11 SP3, RHEL 5.x, RHEL 6.x, OL 5.x and OL 6.x. 
  For example, if powermt display lists HBAs 8 and 9, initiate the scan by typing:
  echo “- - -“ > /sys/class/scsi_host/host8/scan
  echo “- - -“ > /sys/class/scsi_host/host9/scan
  For iSCSI software initiator, type:
  echo “- - -“ > /sys/class/scsi_host/host<controller>/scan

1. Run powermt config to configure the new LUN.
2. Run powermt display to confirm the addition of the new LUN.

or you can use

 echo "1" > /sys/class/fc_host/host1/issue_lip

which requests a lip