Diagnostic Procedure

INSPECTION START
1. Turn ignition switch OFF.
2. Loosen and retighten engine ground screws.
  
  Fig 1: Identifying Engine Ground
  Courtesy of NISSAN MOTOR CO., U.S.A.
  1. GO TO 2.
CHECK HO2S1 GROUND CIRCUIT FOR OPEN AND SHORT
1. Disconnect heated oxygen sensor 1 harness connector.
2. Disconnect ECM harness connector.
3. Check harness continuity between ECM terminal 78 and HO2S1 terminal 4.
  Refer to WIRING DIAGRAM .
  
  Continuity should exist.
4. Also check harness for short to ground and short to power.
Fig 2: Disconnecting Heated Oxygen Sensor 1 Harness Connector
Courtesy of NISSAN MOTOR CO., U.S.A.

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.
CHECK HO2S1 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Check harness continuity between ECM terminal 35 and HO2S1 terminal 1. Refer to WIRING DIAGRAM .
  Continuity should exist.
2. Check harness continuity between ECM terminal 35, HO2S1 terminal 1 and ground. Refer to WIRING DIAGRAM .
  Continuity should not exist.
3. 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.
CHECK HEATED OXYGEN SENSOR 1
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 5.
2. NG: Replace heated oxygen sensor 1.
CHECK INTERMITTENT INCIDENT
Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".
1. INSPECTION END