3. Check A/F Sensor 1 Input Signal Circuit

1. Turn ignition switch OFF.
2. Disconnect corresponding A/F sensor 1 harness connector.
   Fig 1: Disconnect Corresponding A/F Sensor 1 Harness Connector

   Courtesy of NISSAN MOTOR CO., U.S.A.
3. Disconnect ECM harness connector.
4. Check harness continuity between the following terminals.

   Refer to WIRING DIAGRAM.

   Fig 2: Check Harness Continuity Between The Following Terminals

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

   Refer to WIRING DIAGRAM.

   Fig 3: Check Harness Continuity Between The Following Terminals And Ground

   Courtesy of NISSAN MOTOR CO., U.S.A.
   1. Continuity should not exist. 
6. Also check harness for short to power.

OK or NG 

1. OK: GO TO 4.
2. NG: Repair open circuit or short to ground or short to power in harness or connectors.