One usually sees one of two designs on Nissan connectors. The problem with either one is that dirt can get under the tab and make it difficult to get the connector to release. Compressed air can be helpful in blowing out the dirt. The one type of connector you just press down on the tab and pull the connector off. The other style usually has a green colored release tab. On those, I push the connector forward, then push the green release forward to release the locking mechanism and then pull the connector off while keeping the tab pushed forward.