2. Check HO2S2 Ground Circuit For Open And Short

1. Disconnect ECM harness connector.
2. Disconnect heated oxygen sensor 2 harness connector.
   Fig 1: Locating Heated Oxygen Sensor 2 Harness Connectors

   Courtesy of NISSAN MOTOR CO., U.S.A.
3. Check harness continuity between ECM terminal 78 and HO2S2 terminal 3.

   Refer to WIRING DIAGRAM.

   1. Continuity should exist. 
4. Also check harness for short to ground or short to power.

OK or NG 

1. OK: GO TO 3.
2. NG: Repair open circuit or short to ground or short to power in harness or connectors.