Nissan Murano: Dtc/circuit Diagnosis / P0171 Fuel Injection System Function

DTC Description

DTC DETECTION LOGIC

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from A/F sensor 1. The ECM calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (the actual mixture ratio is too lean), the ECM judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).

1. Fuel injection system does not operate properly.

2. The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.)

POSSIBLE CAUSE

P0171

• Intake air leakage

• A/F sensor 1

• Fuel injector

• Exhaust gas leakage

• Incorrect fuel pressure

• Lack of fuel

• Mass air flow sensor

• Incorrect PCV hose connection

P0174

• Intake air leakage

• A/F sensor 1

• Fuel injector

• Exhaust gas leakage

• Incorrect fuel pressure

• Lack of fuel

• Mass air flow sensor

• Incorrect PCV hose connection

FAIL-SAFE

Not applicable

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.

2. Turn ignition switch ON.

3. Turn ignition switch OFF and wait at least 10 seconds.

GO TO 2.

PERFORM DTC CONFIRMATION PROCEDURE-I

1. Clear the mixture ratio self-learning value. Refer to Description.

2. Start engine.

Is it difficult to start engine?

GO TO 3.

GO TO 4.

RESTART ENGINE

If it is difficult to start engine, the fuel injection system has a malfunction, too.

Crank engine while depressing accelerator pedal.

NOTE:

• When depressing accelerator pedal three-fourths (3/4) or more, the control system does not start the engine. Do not depress accelerator pedal too much.

Does engine start?

Proceed to Diagnosis Procedure.

Check exhaust and intake air leakage visually.

PERFORM DTC CONFIRMATION PROCEDURE-II

1. Keep engine idle for at least 5 minutes.

2. Check 1st trip DTC.

Is 1st trip DTC detected?

Proceed to Diagnosis Procedure.

GO TO 5.

PERFORM DTC CONFIRMATION PROCEDURE-III

1. Turn ignition switch OFF and wait at least 10 seconds.

2. Start engine.

3. Maintain the following conditions for at least 10 consecutive minutes.

   Hold the accelerator pedal as steady as possible.

   VHCL SPEED SE

   50 - 120 km/h (31 - 75 mph)

   CAUTION:

   Always drive Nissan Murano vehicle at a safe speed.

4. Check 1st trip DTC.

Is 1st trip DTC detected?

Proceed to Diagnosis Procedure.

To check malfunction symptom before repair: Refer to Intermittent Incident.

Confirmation after repair: INSPECTION END

CHECK EXHAUST GAS LEAKAGE

1. Start engine and run it at idle.

2. Listen for an exhaust gas leakage before three way catalyst (manifold).

   

Is exhaust gas leakage detected?

Repair or replace malfunctioning part.

GO TO 2.

CHECK FOR INTAKE AIR LEAKAGE

1. Listen for an intake air leakage after the mass air flow sensor.

2. Check PCV hose connection.

Is intake air leakage detected?

Repair or replace malfunctioning part.

GO TO 3.

CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT

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.

   DTC	A/F sensor 1			ECM		Continuity
   	Bank	Connector	Terminal	Connector	Terminal
   P0171	1	F12	3	F79	66	Existed
   			4		67
   P0174	2	F61	3		76
   			4		77

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

   DTC	A/F sensor 1			Ground	Continuity
   	Bank	Connector	Terminal
   P0171	1	F12	3	Ground	Not existed
   			4
   P0174	2	F61	3
   			4

   DTC	ECM		Ground	Continuity
   	Connector	Terminal
   P0171	F79	66	Ground	Not existed
   		67
   P0174		76
   		77

6. Also check harness for short to power.

Is the inspection result normal?

GO TO 4.

Repair open circuit, short to ground or short to power in harness or connectors.

CHECK A/F SENSOR 1 FUNCTION CHECK-1

If DTC Confirmation Procedure has been previously conducted, always perform the following before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.

2. Turn ignition switch ON.

3. Turn ignition switch OFF and wait at least 10 seconds.

TESTING CONDITION:

Before performing the following procedure, confirm that battery voltage is more than 11 V at idle.

GO TO 5.

CHECK A/F SENSOR 1 FUNCTION CHECK-2

1. Clear the mixture ratio self-learning value. Refer to Description.

2. Turn ignition switch OFF and wait at least 10 seconds.

3. Turn ignition switch ON.

4. Turn ignition switch OFF and wait at least 10 seconds.

5. Start engine and keep the engine speed between 3,500 and 4,000 rpm for 1 minute under no load.

6. Let engine idle for 1 minute.

7. Keep engine speed between 2,500 and 3,000 rpm for 20 minutes.

8. Check DTC.

Is DTC detected?

Replace A/F sensor. Refer to Exploded View.

GO TO 6.

CHECK FUEL PRESSURE

Check fuel pressure. Refer to Work Procedure.

Is the inspection result normal?

GO TO 8.

GO TO 7.

DETECT MALFUNCTIONING PART

Check fuel hoses and fuel tubes for clogging.

Is the inspection result normal?

Replace “fuel filter and fuel pump assembly”. Refer to Removal and Installation.

Repair or replace malfunctioning part.

CHECK MASS AIR FLOW SENSOR

With CONSULT

1. Install all removed parts.

2. Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT.

   For specification, refer to Component Inspection.

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?

GO TO 9.

Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or ground. Refer to Diagnosis Procedure.

CHECK FUNCTION OF FUEL INJECTOR

With CONSULT

1. Start engine.

2. Perform “POWER BALANCE” in “ACTIVE TEST” mode with CONSULT.

3. Check that each circuit produces a momentary engine speed drop.

With GST

1. Let engine idle.

2. Listen to each fuel injector operating sound.

   

Is the inspection result normal?

GO TO 10.

Perform trouble diagnosis for FUEL INJECTOR, refer to Diagnosis Procedure.

CHECK FUEL INJECTOR

1. Turn ignition switch OFF.

2. Confirm that the engine is cooled down and there are no fire hazards near the Nissan Murano 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, check that fuel sprays out from fuel injectors on bank 1.

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

   Fuel should be sprayed evenly for each fuel injector.

Is the inspection result normal?

INSPECTION END

Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones. Refer to Removal and Installation.