Nissan Sentra. Manual - part 388

EC-248

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

P0171 FUEL INJECTION SYSTEM FUNCTION

*2: For California

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

and ground.

*1: Except California

*2: For California

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

YES

>> GO TO 4.

NO

>> Repair or replace error-detected parts.

4.

CHECK FUEL PRESSURE

Check fuel pressure. Refer to 

EC-143, "Work Procedure"

.

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. Refer to 

EM-40, "Exploded View"

.

Is the inspection result normal?

YES

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

FL-6, "Exploded View"

.

NO

>> Repair or replace error-detected parts.

6.

CHECK MASS AIR FLOW SENSOR

With CONSULT

1. Install all removed parts.

2. Check “MASS AIR FLOW” in “DATA MONITOR” mode of “ENGINE” using CONSULT.

3. For specification, refer to 

EC-486, "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-486, "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-186, "DTC Logic"

.

7.

CHECK FUNCTION OF FUEL INJECTOR

With CONSULT

1. Start engine.

2. Perform “POWER BALANCE” in “ACTIVE TEST” mode of “ENGINE” using CONSULT.

3. Make sure that each circuit produces a momentary engine speed drop.

+

−

Continuity

A/F sensor 1

Connector

Terminal

F12

*1

F42

*2

1

Ground

Not existed

2

+

−

Continuity

ECM

Connector

Terminal

F24

41

Ground

Not existed

45

P0171 FUEL INJECTION SYSTEM FUNCTION

EC-249

< DTC/CIRCUIT DIAGNOSIS >

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Without CONSULT

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-450, "Component Function Check"

.

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. 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

>> Check intermittent incident. Refer to 

GI-39, "Intermittent

Incident"

.

NO

>> Replace fuel injectors from which fuel does not spray

out. Always replace O-ring with new ones. Refer to 

EM-

40, "Removal and Installation"

.

Clicking noise should be heard.

PBIB3332E

Fuel should be sprayed evenly for each fuel injector.

PBIA9666J

EC-250

< DTC/CIRCUIT DIAGNOSIS >

[MRA8DE]

P0172 FUEL INJECTION SYSTEM FUNCTION

P0172 FUEL INJECTION SYSTEM FUNCTION

DTC Logic

INFOID:0000000009758500

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 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-1

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

EC-142, "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-251, "Diagnosis Procedure"

.

NO

>> Check exhaust and intake air leak visually.

4.

PERFORM DTC CONFIRMATION PROCEDURE-2

1. Start engine and let it idle for at least 5 minutes.

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

YES

>> Proceed to 

EC-251, "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 con-

tent)

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 leaks
• Incorrect fuel pressure
• Mass air flow sensor

P0172 FUEL INJECTION SYSTEM FUNCTION

EC-251

< DTC/CIRCUIT DIAGNOSIS >

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5.

PERFORM DTC CONFIRMATION PROCEDURE-3

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-251, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000009758501

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 error-detected parts.

NO

>> GO TO 2.

2.

CHECK FOR INTAKE AIR LEAK

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

YES

>> Repair or replace error-detected parts.

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.

*1: Except California

*2: For California

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

+

−

Continuity

A/F sensor 1

ECM

Connector

Terminal

Connector

Terminal

F12

*1

F42

*2

1

F24

41

Existed

2

45