During configuration phase of Grid Infrastructure for cluster, CVU failed while performing post-checks.
Following message is displaced in the Installation Log file:

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">Checking Single Client Access Name (SCAN)...</span></span>

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">WARNING:
<strong>PRVF-5056</strong> : Scan Listener "LISTENER" not running</span></span>

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">Checking name resolution setup for "scan-test.abc.com"...</span></span>

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">Verification of SCAN VIP and Listener setup failed</span></span>

The LISTENER from Grid Infrastructure home is running fine:

$ ps -eaf | grep tns

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">/u01/app/grid_11.2/GridInfra/bin/tnslsnr LISTENER -inherit</span></span>

Same error is observerd by manually runnig CVU as:

$ cluvfy comp scan

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">Verifying scan
Checking Single Client Access Name (SCAN)...</span></span>

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">WARNING:
<strong>PRVF-5056 </strong>: Scan Listener "LISTENER" not running</span></span>

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">Checking name resolution setup for "scan-test.abc.com"...
Verification of SCAN VIP and Listener setup failed
Verification of scan was unsuccessful on all the specified nodes.</span></span>

Checking the status of SCAN using SRVCTL gives correct results:

$ srvctl config scan

SCAN name: scan-test.abc.com, Network: 1/165.101.124.0/255.255.254.0/eth0
<span style="font-size: small;">SCAN VIP name: scan1, IP: /scan-test.abc.com/165.101.125.204
SCAN VIP name: scan2, IP: /scan-test.abc.com/165.101.125.235
SCAN VIP name: scan3, IP: /scan-test.abc.com/165.101.125.180</span>

Which shows that the SCAN is configured properly.

When I tried to start the SCAN Listener manually as:

$ srvctl start scan_listener

It showed the following results:

node1:
====

<span style="font-size: small;">oracle 379 1 0 07:53 ? 00:00:00 /u01/app/grid_11.2/GridInfra/bin/tnslsnr LISTENER_SCAN1 -inherit
oracle 401 1 0 07:53 ? 00:00:00 /u01/app/grid_11.2/GridInfra/bin/tnslsnr LISTENER_SCAN3 -inherit</span>

node2:
====

<span style="font-size: small;"><span style="font-family: arial,helvetica,sans-serif;">oracle 11726 1 0 07:53 ? 00:00:00 /u01/app/grid_11.2/GridInfra/bin/tnslsnr LISTENER_SCAN2 -inherit</span></span>

$ srvctl config scan_listener

<span style="font-size: small;">SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521
SCAN Listener LISTENER_SCAN2 exists. Port: TCP:1521
SCAN Listener LISTENER_SCAN3 exists. Port: TCP:1521</span>

After this, I clicked at the retry button for the CVU post checks and this time it succeeded.
Though it worked fine after this, but still not sure why I have to manually start the SCAN-Listeners !!!!!

Cheers!!!!