The vPC consistency check message is sent by the vPC peer link. The vPC consistency check cannot be performed when the peer link is lost. When the vPC peer link is lost, the operational secondary switch suspends all of its vPC member ports while the vPC member ports remain on the operational primary switch. If the vPC member ports on the primary switch flaps afterwards (for example, when the switch or server that connects to the vPC primary switch is reloaded), the ports remain down due to the vPC consistency check and you cannot add or bring up more vPCs.
Beginning with Cisco NX-OS Release 5.0(2)N2(1), the auto-recovery feature brings up the vPC links when one peer is down. This feature performs two operations:
*

If both switches reload, and only one switch boots up, auto-recovery allows that switch to assume the role of the primary switch. The vPC links come up after a configurable period of time if the vPC peer-link and the peer-keepalive fail to become operational within that time.
If the peer-link comes up but the peer-keepalive does not come up, both peer switches keep the vPC links down. This feature is similar to the reload restore feature in Cisco NX- OS Release 5.0(2)N1(1) and earlier releases. The reload delay period can range from 240 to 3600 seconds.

* When you disable vPCs on a secondary vPC switch because of a peer-link failure and then the primary vPC switch fails, the secondary switch reenables the vPCs. In this scenario, the vPC waits for three consecutive keepalive failures before recovering the vPC links.
Reference:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/operations/n5k_v pc_ops.html