4PCS 02 Oxygen O2 Sensor Upstream + Downstream For 2007 Nissan Frontier V6 4.0L

Frontier 4.0L V6 2007 2008 2009 2010. Q: How do I know the O2 sensor is good or not?. Pathfinder 4.0L V6 2007 2008 2009 2010. Xterra 4.0L V6 2007 2008 2009 2010. Equator 4.0L V6 2009 2010. If the sensor is good, further diagnosis is required.