Diagnostic Procedure

RETIGHTEN GROUND SCREWS
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.
RETIGHTEN HEATED OXYGEN SENSOR 1
Loosen and retighten heated oxygen sensor 1.

Fig 2: Identifying Heated Oxygen Sensor 1
Courtesy of NISSAN MOTOR CO., U.S.A.

Tightening torque: 40 - 60 N.m (4.1 - 6.1 kg-m, 30 - 44 ft-lb)
1. GO TO 3.
CHECK FOR EXHAUST GAS LEAK
1. Start engine and run it at idle.
2. Listen for an exhaust gas leak before three way catalyst (Manifold).
  
  Fig 3: Checking For Exhaust Gas Leak
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG
1. OK: GO TO 4.
2. NG: Repair or replace.
CHECK FOR INTAKE AIR LEAK
Listen for an intake air leak after the mass air flow sensor.

OK or NG
1. OK: GO TO 5.
2. NG: Repair or replace.
CLEAR THE SELF-LEARNING DATA
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-II.
3. Clear the self-learning control coefficient by touching "CLEAR".
4. Run engine for at least 10 minutes at idle speed.
  Is the 1st trip DTC P0171 or P0172 detected?
  
  Is it difficult to start engine?
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF.
3. Disconnect mass air flow sensor harness connector, and restart and run engine for at least 5 seconds at idle speed.
4. Stop engine and reconnect mass air flow sensor harness connector.
5. Make sure DTC P0102 is displayed.
6. Erase the DTC memory. Refer to "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION ".
7. Make sure DTC P0000 is displayed.
8. Run engine for at least 10 minutes at idle speed.
  Is the 1st trip DTC P0171 or P0172 detected?
  
  Is it difficult to start engine?
  
  Fig 5: Identifying Mass Air Flow Sensor Harness Connector
  Courtesy of NISSAN MOTOR CO., U.S.A.
Yes or No
1. Yes: perform trouble diagnosis for DTC P0171 or DTC P0172 (Refer to DTC P0171 FUEL INJECTION SYSTEM FUNCTION or DTC P0172 FUEL INJECTION SYSTEM FUNCTION .).
2. No: GO TO 6.
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 6: Identifying Heated Oxygen Sensor 1 Harness Connector
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG
1. OK: GO TO 7.
2. NG: Repair open circuit or short to ground 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 or 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 8.
2. NG: Repair open circuit or short to ground or short to power in harness or connectors.
CHECK HEATED OXYGEN SENSOR 1 HEATER
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 9.
2. NG: Replace heated oxygen sensor 1.
CHECK MASS AIR FLOW SENSOR
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 10.
2. NG: Replace mass air flow sensor.
CHECK PCV VALVE
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 11.
2. NG: Replace PCV valve.
CHECK HEATED OXYGEN SENSOR 1
Refer to "COMPONENT INSPECTION ".

OK or NG
1. OK: GO TO 12.
2. NG: Replace heated oxygen sensor 1.
CHECK INTERMITTENT INCIDENT
Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ".
1. INSPECTION END