Nissan Pathfinder. Manual - part 487

EC-254

< DTC/CIRCUIT DIAGNOSIS >

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

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?

YES

>> GO TO 8.

NO

>> Perform trouble diagnosis for FUEL INJECTOR, refer to

EC-430, "Diagnosis Procedure"

.

8.

CHECK FUEL INJECTOR

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 

EM-47, "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.

Is the inspection result normal?

YES

>> Check intermittent incident. Refer to 

GI-49, "Intermittent Incident"

.

NO

>> Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones.

Refer to 

EM-47, "Removal and Installation"

.

PBIB3332E

Fuel should be sprayed evenly for each fuel injector.

P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

EC-255

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P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

DTC Logic

INFOID:0000000009178170

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 rich), the ECM

judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection logic).

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-

ing 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.

2.

PERFORM DTC CONFIRMATION PROCEDURE-I

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

EC-145, "Work Procedure"

.

2. Start engine.
Is it difficult to start engine?

YES

>> GO TO 3.

NO

>> GO TO 4.

3.

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?

YES

>> Proceed to 

EC-257, "Diagnosis Procedure"

.

NO

>> Check exhaust and intake air leakage visually.

4.

PERFORM DTC CONFIRMATION PROCEDURE-II

1. Keep engine idle for at least 5 minutes.

2. Check 1st trip DTC.
Is 1st trip DTC detected?

YES

>> Proceed to 

EC-257, "Diagnosis Procedure"

.

NO

>> GO TO 5.

Sensor

Input signal to ECM

ECM function

Actuator

A/F sensor 1

Density of oxygen in exhaust gas
(Mixture ratio feedback signal)

Fuel injection control

Fuel injector

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition 

Possible cause

P0172

FUEL SYS-RICH-B1
(System too rich bank 1)

• Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too 

large. (The mixture ratio is too rich.)

• A/F sensor 1
• Fuel injector
• Exhaust gas leakage
• Incorrect fuel pressure
• Mass air flow sensor

P0175

FUEL SYS-RICH-B2
(System too rich bank 2)

EC-256

< DTC/CIRCUIT DIAGNOSIS >

[VQ35DE]

P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

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.

CAUTION:

Always drive vehicle at a safe speed.

4. Check 1st trip DTC.
Is 1st trip DTC detected?

YES

>> Proceed to 

EC-257, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000009178171

1.

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?

YES

>> Repair or replace malfunctioning part.

NO

>> GO TO 2.

2.

CHECK FOR INTAKE AIR LEAKAGE

Listen for an intake air leakage after the mass air flow sensor.
Is intake air leakage detected?

YES

>> Repair or replace malfunctioning part.

NO

>> GO TO 3.

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.

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

and ground.

VHCL SPEED SE

50 - 120 km/h (31 - 75 mph)

PBIB1216E

DTC

A/F sensor 1

ECM

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0172

1

F5

1

F52

69

Existed

2

73

P0175

2

F65

1

77

2

81

P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

EC-257

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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.

4.

CHECK FUEL PRESSURE

1. Release fuel pressure to zero. Refer to 

EC-151, "Work Procedure"

.

2. Install fuel pressure gauge kit [SST: — (J-44321)] and check fuel pressure. Refer to 

EC-151, "Work Proce-

dure"

.

Is the inspection result normal?

YES

>> GO TO 5.

NO

>> Replace “fuel filter and fuel pump assembly”. Refer to 

FL-6, "Removal and Installation"

.

5.

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 

EC-467, "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 

EC-467, "Mass Air Flow Sensor"

.

Is the measurement value within the specification?

YES

>> GO TO 6.

NO

>> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or

ground. Refer to 

EC-196, "Diagnosis Procedure"

.

6.

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.

DTC

A/F sensor 1

Ground

Continuity

Bank

Connector

Terminal

P0172

1

F5

1

Ground

Not existed

2

P0175

2

F65

1

2

DTC

ECM

Ground

Continuity

Connector

Terminal

P0172

F52

69

Ground

Not existed

73

P0175

77

81

At idling: Approximately 350 kPa (3.57 kg/cm

2

, 51 psi)