Nissan Frontier D40. Manual - part 370

P0171 FUEL INJECTION SYSTEM FUNCTION

EC-171

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2.

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

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace.

2.

CHECK FOR INTAKE AIR LEAK 

1.

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

2.

Check PCV hose connection.

OK or NG

OK

>> GO TO 3.

NG

>> Repair or replace.

3.

CHECK AIR FUEL RATIO (A/F) SENSOR 1 CIRCUIT FOR OPEN AND SHORT

1.

Turn ignition switch OFF.

2.

Disconnect A/F sensor 1 harness connector and ECM harness
connector.

3.

Check harness continuity between ECM terminals and A/F sen-
sor 1 terminals as follows.
Refer to Wiring Diagram.

4.

Check harness continuity between ECM terminals 16, 35, 56, 75 and ground, or A/F sensor 1 terminals 1,
2, 5, 6 and ground.
Refer to Wiring Diagram.

5.

Also check harness for short to power.

OK or NG

OK

>> GO TO 4.

NG

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

4.

CHECK FUEL PRESSURE

1.

Release fuel pressure to zero. Refer to 

EC-454, "Fuel Pressure Check"

.

2.

Install fuel pressure gauge kit [SST (J-44321)] and check fuel pressure. Refer to 

EC-454, "Fuel Pressure

Check"

.

OK or NG

OK

>> GO TO 6.

PBIB1216E

A/F sensor 1

ECM terminal

1

16

2

75 

5

35

6

56

Continuity should exist.

Continuity should not exist.

BBIA0617E

At idling: Approximately 350 kPa (3.57 kg/cm

2

, 51 psi)

EC-172

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P0171 FUEL INJECTION SYSTEM FUNCTION

NG

>> GO TO 5.

5.

 DETECT MALFUNCTIONING PART

Check the following.
• Fuel pump and circuit (Refer to 

EC-378

.)

• Fuel pressure regulator (Refer to 

EC-454, "Fuel Pressure Check"

.)

• Fuel lines
• Fuel filter for clogging

>> 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.

With GST

1.

Install all removed parts. 

2.

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

OK or NG

OK

>> GO TO 7.

NG

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

grounds. Refer to 

EC-112, "Component Description"

.

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.

Start engine.

2.

Listen to each fuel injector operating sound.

OK or NG

OK 

>> GO TO 8.

NG

>> Perform trouble diagnosis for 

EC-375

.

8.

CHECK FUEL INJECTOR

1.

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

2.

Turn ignition switch OFF.

3.

Disconnect fuel injector harness connectors.

At idling:

1.0 - 4.0 g·m/sec

At 2,500 rpm:

4.0 - 12.0 g·m/sec

At idling:

1.0 - 4.0 g·m/sec

At 2,500 rpm:

4.0 - 12.0 g·m/sec

Clicking noise should be heard.

PBIB1986E

P0171 FUEL INJECTION SYSTEM FUNCTION

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4.

Remove fuel injector gallery assembly. Refer to 

EM-38, "Removal and Installation"

.

Keep fuel hose and all fuel injectors connected to fuel injector gallery.
The fuel injector harness connectors should remain connected.

5.

Disconnect all ignition coil harness connectors.

6.

Prepare pans or saucers under each fuel injector.

7.

Crank engine for about 3 seconds. Make sure that fuel sprays
out from fuel injectors.

OK or NG

OK

>> GO TO 9. 

NG

>> Replace fuel injectors from which fuel does not spray

out. Always replace O-ring with new ones.

9.

CHECK INTERMITTENT INCIDENT

Perform 

GI-46, "Intermittent Incident"

.

>> INSPECTION END

Fuel should be sprayed evenly for each fuel injector.

PBIB1726E

EC-174

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P0172 FUEL INJECTION SYSTEM FUNCTION

P0172 FUEL INJECTION SYSTEM FUNCTION

On Board Diagnosis Logic

INFOID:0000000005273164

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 sensor 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

INFOID:0000000005550908

NOTE:
If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at
least 10 seconds before conducting the next test.

 WITH CONSULT-III

1.

Start engine and warm it up to normal operating temperature.

2.

Turn ignition switch OFF and wait at least 10 seconds.

3.

Turn ignition switch ON and select “SELF-LEARNING CONT” in “WORK SUPPORT” mode with CON-
SULT-III.

4.

Clear the self-learning control coefficient by touching “CLEAR”.

5.

Start engine.
If it is difficult to start engine, the fuel injection system has a malfunction.
Performing the following procedure is advised.

a.

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.

b.

If engine starts, go to 

EC-175, "Diagnosis Procedure"

.

If engine does not start, remove ignition plugs and check for fouling, etc.

6.

Keep engine at idle for at least 5 minutes.

7.

Check 1st trip DTC.

8.

The 1st trip DTC P0172 should be detected at this stage, if a malfunction exists. If so, go to 

EC-175,

"Diagnosis Procedure"

.

NOTE:
If 1st trip DTC is not detected during above procedure, performing the following procedure is advised.

a.

Turn ignition switch OFF and wait at least 10 seconds.

b.

Start engine.

c.

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.

Sensor

Input Signal to ECM

ECM function

Actuator

Air fuel ratio (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
0172

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.)

• Air fuel ratio (A/F) sensor 1
• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Mass air flow sensor

VHCL SPEED SE

50 - 120 km/h (31 - 75 MPH)