Nissan Altima L32. Instruction — part 284

P0171 FUEL INJECTION SYSTEM FUNCTION

EC-257

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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-36, "Removal and Installation"

.

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

5. Disconnect all ignition coil harness connectors.

6. Prepare pans or saucers under each fuel injector.

7. Crank engine for about 3 seconds.

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-42, "Intermittent Incident"

.

>> INSPECTION END

Fuel should be sprayed evenly for each fuel injector.

PBIA9666J

EC-258

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P0172 FUEL INJECTION SYSTEM FUNCTION

P0172 FUEL INJECTION SYSTEM FUNCTION

DTC Logic

INFOID:0000000004349295

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 the A/F sensors 1. The ECM calcu-

lates 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 lights up the MIL (2 trip detection logic).

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at

least 10 seconds before conducting the next test.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE-I

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

EC-32, "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.
Does engine start?

YES

>> Go to

EC-259, "Diagnosis Procedure"

.

NO

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

4.

PERFORM DTC CONFIRMATION PROCEDURE-II

1. Start engine and let it idle for at least 10 minutes.
Is 1st trip DTC detected?

YES

>> Go to

EC-259, "Diagnosis Procedure"

.

NO

>> GO TO 5.

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.

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

• 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

P0172 FUEL INJECTION SYSTEM FUNCTION

EC-259

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[QR25DE FOR CALIFORNIA]

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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

>> Go to

EC-259, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000004349296

1.

CHECK EXHAUST GAS LEAK

1. Start engine and run it at idle.

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

Is exhaust gas leak detected?

YES

>> Repair or replace.

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.

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 or ECM harness connector and ground.

6. Also check harness for short to power.
Is the inspection result normal?

YES

>> GO TO 4.

VHCL SPEED SE

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

JMBIA0163GB

A/F sensor 1

ECM

Continuity

Connector Terminal Connector Terminal

F44

1

F14

45

Existed

2

49

A/F sensor 1

ECM

Ground

Continuity

Connector Terminal Connector Terminal

F44

1

F14

45

Ground Not existed

2

49

EC-260

< COMPONENT DIAGNOSIS >

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P0172 FUEL INJECTION SYSTEM FUNCTION

NO

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

4.

CHECK FUEL PRESSURE

1. Check fuel pressure. Refer to

EC-550, "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

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.

3. For specification, refer to

EC-555, "Mass Air Flow Sensor"

.

With GST

1. Install all removed parts.

2. Check mass air flow sensor signal in “Service $01” with GST.

3. For specification, refer to

EC-555, "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-168, "DTC Logic"

.

7.

CHECK FUNCTION OF FUEL INJECTOR

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. 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-463, "Component Function Check"

.

8.

CHECK FUEL INJECTOR

1. Remove fuel injector assembly. Refer to

EM-36, "Removal and Installation"

.

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

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. Disconnect all ignition coil harness connectors.

5. Prepare pans or saucers under each fuel injectors.

6. Crank engine for about 3 seconds.

Make sure fuel does not drip from fuel injector.

Is the inspection result normal?

Clicking noise should be heard.

PBIB3332E