Diagnostic Procedure

CHECK GROUND CONNECTIONS
1. Turn ignition switch OFF.
2. Loosen and retighten four ground screws on the body.
  Refer to "GROUND INSPECTION ."
  
  Fig 1: Checking Ground Connections
  Courtesy of NISSAN MOTOR CO., U.S.A.
  
  OK or NG
  
  OK: GO TO 2.
  
  NG: Repair or replace ground connections.
CLEAR THE SELF-LEARNING DATA
With CONSULT-III
1. Start engine and warm it up to normal operating temperature.
2. Select "SELF-LEARNING CONT" in "WORK SUPPORT" mode with CONSULT-III.
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, P0172, P0174 or P0175 detected?
  
  Is it difficult to start engine?
Without CONSULT-III
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF.
3. Disconnect mass air flow sensor harness connector.
  - ← : Vehicle front
  - Oil pan (view from under vehicle) (1)
  - Heated oxygen sensor 2 (bank 1) harness connector (2)
  - Heated oxygen sensor 2 (bank 2) harness connector (3)
  Fig 2: Identifying Mass Air Flow Sensor And Air Cleaner
  Courtesy of NISSAN MOTOR CO., U.S.A.
4. Restart engine and let it idle for at least 5 seconds.
5. Stop engine and reconnect mass air flow sensor harness connector.
6. Make sure DTC P0102 is displayed.
7. Erase the DTC memory. Refer to "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION ."
8. Make sure DTC P0000 is displayed.
9. Run engine for at least 10 minutes at idle speed.
  Is the 1st trip DTC P0171, P0172, P0174 or P0175 detected?
  
  Is it difficult to start engine?
Yes or No

YES: Perform trouble diagnosis for DTC P0171, P0174 or P0172, P0175. Refer to "DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION " or "DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION ."

NO: GO TO 3.
CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch OFF.
2. Disconnect ECM harness connector.
3. Disconnect heated oxygen sensor 2 harness connector.
  - Vehicle front
  - Oil pan (view from under vehicle) (1)
  - Heated oxygen sensor 2 (bank 1) harness connector (2)
  - Heated oxygen sensor 2 (bank 2) harness connector (3)
4. Check harness continuity between ECM terminal 78 and HO2S2 terminal 4. Refer to Wiring Diagram.
  Continuity should exist .
5. Also check harness for short to ground or short to power.
  OK or NG
  
  OK: GO TO 4.
  
  NG: Repair open circuit or short to ground and short to power in harness or connectors.

CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

Check harness continuity between ECM terminal and HO2S2 terminal as follows. Refer to Wiring Diagram.

ECM TERMINAL AND HO2S2 TERMINAL

DTC	Terminals		Bank
DTC	ECM	Sensor	Bank
P0139	74	1	1
P0159	55	1	2

Continuity should exist .

Check harness continuity between the following terminals and ground. Refer to Wiring Diagram.

TERMINALS AND GROUND

DTC	Terminals		Bank
DTC	ECM	Sensor	Bank
P0139	74	1	1
P0159	55	1	2

Continuity should not exist .

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.

CHECK HEATED OXYGEN SENSOR 2
Refer to "COMPONENT INSPECTION ."

OK or NG

OK: GO TO 6.

NG: Replace malfunctioning heated oxygen sensor 2.
CHECK INTERMITTENT INCIDENT
Refer to "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT ."

>> INSPECTION END