Infiniti FX35, FX50 (S51). Manual - part 825

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-841

< DTC/CIRCUIT DIAGNOSIS >

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Is 1st trip DTC detected?

YES

>> Go to 

EC-841, "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.

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-841, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000005237320

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

1.

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

2.

Check PCV hose connection.

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.

Vehicle speed

50 - 120 km/h (31 - 75 MPH)

PBIB1216E

EC-842

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

5.

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

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 

EM-173, "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-1241, "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-1241, "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-773, "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.

DTC

A/F sensor 1

ECM

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0171

1

F67

1

F111

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Existed

2

82

P0174

2

F68

1

85

2

86

DTC

A/F sensor 1

ECM

Ground

Continuity

Bank

Connector

Terminal

Connector

Terminal

P0171

1

F67

1

F111

81

Ground

Not existed

2

82

P0174

2

F68

1

85

2

86

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-843

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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-1103, "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-182, "Removal and Installation"

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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

Clicking sound should be heard.

PBIB3332E

Fuel should be sprayed evenly for each fuel injector.

PBIB1726E

EC-844

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P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

DTC Logic

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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 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-585, "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.
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

>> Go to 

EC-845, "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-845, "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.

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 leakage
• Incorrect fuel pressure
• Mass air flow sensor

P0175

Fuel injection system too 
rich (bank 2)