Infiniti FX35, FX50 (S51). Manual - part 674

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-237

< DTC/CIRCUIT DIAGNOSIS >

[VQ35HR]

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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

Check fuel pressure. Refer to 

EC-566, "Inspection"

.

Is the inspection result normal?

YES

>> GO TO 6.

NO

>> GO TO 5.

5.

 DETECT MALFUNCTIONING PART

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 malfunctioning part.

6.

CHECK MASS AIR FLOW SENSOR

With CONSULT-III

1.

Install all removed parts.

2.

Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT-III.
For specification, refer to 

EC-571, "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-571, "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 

EC-176, "Diagnosis Procedure"

.

7.

CHECK FUNCTION OF FUEL INJECTOR

With CONSULT-III

1.

Start engine.

2.

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

3.

Check 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.

Is the inspection result normal?

YES

>> GO TO 8.

NO

>> Perform trouble diagnosis for FUEL INJECTOR, refer to

EC-470, "Diagnosis Procedure"

.

DTC

A/F sensor 1

ECM

Ground

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0171

1

F3

1

F102

57

Ground

Not existed

2

61

P0174

2

F20

1

65

2

66

Clicking sound should be heard.

PBIB3332E

EC-238

< DTC/CIRCUIT DIAGNOSIS >

[VQ35HR]

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

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-40, "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 approximately 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

>> GO TO 9.

NO

>> Replace fuel injectors from which fuel does not spray

out. Always replace O-ring with new ones.

9.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-36, "Intermittent Incident"

.

>> INSPECTION END

Fuel should be sprayed evenly for each fuel injector.

PBIB1726E

P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

EC-239

< DTC/CIRCUIT DIAGNOSIS >

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P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

DTC Logic

INFOID:0000000005236836

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 air fuel ratio (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 procedure
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.

2.

PERFORM DTC CONFIRMATION PROCEDURE-I

1.

Clear the mixture ratio self-learning value. Refer to 

EC-28, "MIXTURE RATIO SELF-LEARNING VALUE

CLEAR : Special Repair Requirement"

.

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.
Does engine start?

YES

>> Go to 

EC-240, "Diagnosis Procedure"

.

NO

>> Remove spark plugs and check for fouling, etc.

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

>> Go to 

EC-240, "Diagnosis Procedure"

.

NO

>> GO TO 5.

5.

PERFORM DTC CONFIRMATION PROCEDURE-III

1.

Turn ignition switch OFF and wait at least 10 seconds.

2.

Turn ignition switch ON.

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.

Trouble diagnosis name

DTC detecting condition 

Possible cause

P0172

Fuel injection 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 leaks
• Incorrect fuel pressure
• Mass air flow sensor

P0175

Fuel injection system too 
rich (bank 2)

EC-240

< DTC/CIRCUIT DIAGNOSIS >

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P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

3.

Turn ignition switch OFF and wait at least 10 seconds.

4.

Start engine.

5.

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.

6.

Check 1st trip DTC.

Is 1st trip DTC detected?

YES

>> Go to 

EC-240, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000005236837

1.

CHECK EXHAUST GAS LEAK

1.

Start engine and run it at idle.

2.

Listen for an exhaust gas leak before three way catalyst 1.

Is exhaust gas leak detected?

YES

>> Repair or replace malfunctioning part.

NO

>> GO TO 2.

2.

CHECK FOR INTAKE AIR LEAK

Listen for an intake air leak after the mass air flow sensor.

Is intake air leak detected?

YES

>> Repair or replace malfunctioning part.

NO

>> GO TO 3.

3.

CHECK AIR FUEL RATIO (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 or ECM harness connector and ground.

VHCL SPEED SE

50 – 120 km/h (31 – 75 mph)

PBIB1922E

DTC

A/F sensor 1

ECM

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0172

1

F3

1

F102

57

Existed

2

61

P0175

2

F20

1

65

2

66