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Nissan X-Trail 32. Manual - part 781

P0172 FUEL INJECTION SYSTEM FUNCTION

EC-253

< DTC/CIRCUIT DIAGNOSIS >

[MR20DD]

P0172 FUEL INJECTION SYSTEM FUNCTION

DTC Description

INFOID:0000000010775159

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

POSSIBLE CAUSE

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

FAIL-SAFE

DTC CONFIRMATION PROCEDURE

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure
before conducting the next test.

>> GO TO 2.

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

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.)

Engine operating condition in fail-safe mode

Fail safe mode

Vehicle behavior

Traveling con-
trol mode

Accelerator an-
gle variation
control

ECM controls the accelerator pedal depression speed to make it slower than actual speed. This
causes a drop in accelerating performance and encourages the driver to repair malfunction.
NOTE:
ECM does not control the accelerator pedal releasing speed.

Combustion
control mode

Stratified charge
combustion
control at start-
ing

No stratified charge combustion at starting (cold start).

Idle speed con-
trol

Stops feedback control of idle speed and controls with specified speed.

Recovery speed
control at decel-
erating

Stops recovery speed control by the fuel cut at decelerating and controls with specified speed.

Idle neutral con-
trol

Stops idle neutral control.

EC-254

< DTC/CIRCUIT DIAGNOSIS >

[MR20DD]

P0172 FUEL INJECTION SYSTEM FUNCTION

PERFORM DTC CONFIRMATION PROCEDURE-1

Clear the mixture ratio self-learning value. Refer to

EC-148, "Work Procedure"

Start engine.

Is it difficult to start engine?

YES

>> GO TO 3.

>> GO TO 4.

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-254, "Diagnosis Procedure"

>> Check exhaust and intake air leakage visually.

PERFORM DTC CONFIRMATION PROCEDURE-2

Keep engine idle for at least 10 minutes.

Check 1st trip DTC.

Is 1st trip DTC detected?

YES

>> Proceed to

EC-254, "Diagnosis Procedure"

>> GO TO 5.

PERFORM DTC CONFIRMATION PROCEDURE-3

Turn ignition switch OFF and wait at least 10 seconds.

Start engine and maintain the following conditions for at least 10 consecutive minutes. Hold the accelera-
tor pedal as steady as possible.

CAUTION:

Always drive vehicle at a safe speed.

Check 1st trip DTC.

Is 1st trip DTC detected?

YES

>> Proceed to

EC-254, "Diagnosis Procedure"

NO-1

>> To check malfunction symptom before repair: Refer to

GI-44, "Intermittent Incident"

NO-2

>> Confirmation after repair: INSPECTION END

Diagnosis Procedure

INFOID:0000000010775160

CHECK EXHAUST GAS LEAKAGE

Start engine and run it at idle.

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

Is exhaust gas leakage detected?

YES

>> Repair or replace malfunctioning part.

Vehicle
speed

50 - 100 km/h (31 - 62 MPH)

PBIB1216E

P0172 FUEL INJECTION SYSTEM FUNCTION

EC-255

< DTC/CIRCUIT DIAGNOSIS >

[MR20DD]

>> GO TO 2.

CHECK FOR INTAKE AIR LEAKAGE

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

Check PCV hose connection.

Is intake air leakage detected?

YES

>> Repair or replace malfunctioning part.

>> GO TO 3.

CHECK A/F SENSOR 1 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

Turn ignition switch OFF.

Disconnect corresponding A/F sensor 1 harness connector.

Disconnect ECM harness connector.

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

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

Also check harness for short to ground and short to power.

Is the inspection result normal?

YES

>> GO TO 4.

>> Repair or replace malfunctioning part.

CHECK FUEL PRESSURE

Install all removed parts.

Release fuel pressure to 0. Refer to

EC-152, "Work Procedure"

Set a fuel pressure meter and check fuel pressure. Refer to

EC-152, "Work Procedure"

Is the inspection result normal?

YES

>> GO TO 5.

>> Replace malfunctioning fuel gauge unit. Refer to

EC-152, "Work Procedure"

CHECK MASS AIR FLOW SENSOR

WITH CONSULT

Install all removed parts.

−

Continuity

A/F sensor 1

ECM

Connector

Terminal

Connector

Terminal

F27

Existed

Ground

Continuity

A/F sensor 1

Connector

Terminal

F27

Ground

Not existed

Ground

Continuity

ECM

Connector

Terminal

Ground

Not existed

At idle: 500 kPa (5.0 bar, 5.1 kg/cm

, 73 psi)

EC-256

< DTC/CIRCUIT DIAGNOSIS >

[MR20DD]

P0172 FUEL INJECTION SYSTEM FUNCTION

Start engine and warm it up to normal operating temperature.

Check “MASS AIR FLOW” in “DATA MONITOR” mode with CONSULT.

*: Check for linear voltage rise in response to increase of engine speed.

WITHOUT CONSULT

Install all removed parts.

Start engine and warm it up to normal operating temperature.

Check the voltage between ECM harness connector terminals under the following conditions.

*: Check for linear voltage rise in response to increase of engine speed.

Is the inspection result normal?

YES

>> GO TO 6.

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

grounds. Refer to

EC-197, "Diagnosis Procedure"

CHECK FUNCTION OF FUEL INJECTOR

WITH CONSULT

Start engine.

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

Check that each circuit produces a momentary engine speed drop.

WITHOUT CONSULT

Start engine and let it idle.

Listen to each fuel injector operating sound.

Is the inspection result normal?

YES

>> GO TO 7.

>> Perform trouble diagnosis for fuel injector and circuit,

refer to

EC-386, "Diagnosis Procedure"

CHECK FUEL INJECTOR

Turn ignition switch OFF.

Confirm that the engine is cooled down and there are no fire hazards near the vehicle.

Remove fuel tube assembly. Refer to

EM-48, "Exploded View"

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

The fuel injector harness connectors should remain connected.

Disconnect all ignition coil harness connectors.

Prepare pans or saucers under each fuel injector.

Monitor item

Condition

Indication

A/F SEN1 (B1)

Ignition switch ON (Engine stopped.)

Approx. 0.4 V

Idle (Engine is warmed-up to normal op-
erating temperature.)

0.7 - 1.2 V

Idle to about 4,000 rpm

0.7 -1.2 V

→

2.4 V*

ECM

Condition

Voltage

Connector

–

Terminal

Ignition switch ON (Engine stopped.)

Approx. 0.4 V

Idle (Engine is warmed-up to normal
operating temperature.)

0.7 -1.2 V

Idle to about 4,000 rpm

0.7 -1.2 V

→

2.4 V*

Clicking sound should
be heard.

PBIB3332E

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