Diagnosis Procedure

1. Start engine and run it at idle.
2. Listen for an exhaust gas leak before three way catalyst 1.
   Fig 1: Identifying Exhaust Gas Flow In Three Way Catalyst (1 And 2)

   Courtesy of NISSAN MOTOR CO., U.S.A.

   Is exhaust gas leak detected? 

   YES: Repair or replace.

   NO: GO TO 2.

1. Listen for an intake air leak after the mass air flow sensor.
2. Check PCV hose connection.

   Is intake air leak detected? 

   YES: Repair or replace.

   NO: GO TO 3.

1. Turn ignition switch OFF.
2. Disconnect corresponding A/F sensor 1 harness connector.
3. Disconnect ECM harness connector.
4. Check the continuity between A/F sensor 1 harness connector and ECM harness connector.
   CONTINUITY REFERENCE
   
   

   DTC	A/F sensor 1			ECM		Continuity
   	Bank	Connector	Terminal	Connector	Terminal
   P0171	1	F3	1	F102	57	Existed
   			2		61
   P0174	2	F20	1		65
   			2		66

5. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector and ground.
   CONTINUITY REFERENCE
   
   

   DTC	A/F sensor 1			Ground	Continuity
   	Bank	Connector	Terminal
   P0171	1	F3	1	Ground	Not existed
   			2
   P0174	2	F20	1
   			2

   CONTINUITY REFERENCE
   
   

   DTC	ECM			Ground	Continuity
   	Bank	Connector	Terminal
   P0171	1	F102	57	Ground	Not existed
   			61
   P0174	2		65
   			66

6. Also check harness for short to power.

   Is the inspection result normal? 

   YES: GO TO 4.

   NO: Repair open circuit, short to ground or short to power in harness or connectors.

1. Release fuel pressure to zero. Refer to "WORK PROCEDURE ".
2. Install fuel pressure gauge and check fuel pressure. Refer to "WORK PROCEDURE ".

   At idling: Approximately 350 kPa (3.57 kg/cm ²  , 51 psi) 

   Is the inspection result normal? 

   YES: GO TO  6.

   NO: GO TO 5.

Check fuel hoses and fuel tubes for clogging.

Is the inspection result normal? 

YES: Replace "fuel filter and fuel pump assembly".

NO: Repair or replace.

With CONSULT-III 

1. Install all removed parts.
2. Check "MASS AIR FLOW" in "DATA MONITOR" mode with CONSULT-III.

   For specification, refer to "MASS AIR FLOW SENSOR ".

With GST 

1. Install all removed parts.
2. Check mass air flow sensor signal in Service $01 with GST.

   For specification, refer to "MASS AIR FLOW SENSOR ".

   Is the measurement value within the specification? 

   YES: GO TO 7.

   NO: Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or grounds. Refer to "DIAGNOSIS PROCEDURE ".

With CONSULT-III 

1. Start engine.
2. Perform "POWER BALANCE" in "ACTIVE TEST" mode with CONSULT-III.
3. Make sure that each circuit produces a momentary engine speed drop.

Without CONSULT-III 

1. Start engine and let it idle.
2. Listen to each fuel injector operating sound.

   Clicking sound should be heard. 

   Is the inspection result normal? 

   YES: GO TO 8.

   NO: Perform trouble diagnosis for FUEL INJECTOR, refer to "DIAGNOSIS PROCEDURE ".

   Fig 2: Identifying Fuel Injector Operating Sound

   Courtesy of NISSAN MOTOR CO., U.S.A.

1. Turn ignition switch OFF.
2. Confirm that the engine is cooled down and there are no fire hazards near the vehicle.
3. Disconnect all fuel injector harness connectors.
4. Remove fuel tube assembly. Refer to "REMOVAL AND INSTALLATION ".

   Keep fuel hose and all fuel injectors connected to fuel tube.

5. For DTC P0171, reconnect fuel injector harness connectors on bank 1.

   For DTC P0174, reconnect fuel injector harness connectors on bank 2.

6. Disconnect all ignition coil harness connectors.
7. Prepare pans or saucers under each fuel injector.
8. Crank engine for about 3 seconds.

   For DTC P0171, make sure that fuel sprays out from fuel injectors on bank 1.

   For DTC P0174, make sure that fuel sprays out from fuel injectors on bank 2.

   Fuel should be sprayed evenly for each fuel injector. 

   Fig 3: Identifying Fuel Injector For Even Spraying

   Courtesy of NISSAN MOTOR CO., U.S.A.

   Is the inspection result normal? 

   YES: GO TO 9.

   NO: Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.

Refer to "INTERMITTENT INCIDENT ".

INSPECTION END