4. Check HO2S1 Input Signal Circuit For Open And Short

1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal and HO2S1 terminal as follows.

   Refer to Wiring Diagram.

   Fig 1: Checking harness continuity

   Courtesy of NISSAN MOTOR CO., U.S.A.
   1. Continuity should exist. 
3. Check harness continuity between the following terminals and ground. See Fig 1.

   Refer to Wiring Diagram.

   1. Continuity should not exist. 
4. Also check harness for short to power.

OK or NG 

OK: GO TO 5.

NG: Repair open circuit or short to ground or short to power in harness or connectors.