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Nissan Frontier. Manual - part 415

P0171 FUEL INJECTION SYSTEM FUNCTION

EC-231

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

Check the following.

• Fuel pump and circuit (Refer to

EC-442

• Fuel pressure regulator (Refer to

EC-466, "Fuel Pressure Check"

• Fuel lines

• Fuel filter for clogging

>> Repair or replace.

CHECK MASS AIR FLOW SENSOR

With CONSULT

1. Install all removed parts.

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

With GST

1. Install all removed parts.

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

OK or NG

>> GO TO 7.

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

grounds. Refer to

EC-168, "Component Description"

CHECK FUNCTION OF FUEL INJECTOR

With CONSULT

1. Start engine.

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

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

Without CONSULT

1. Start engine.

2. Listen to each fuel injector operating sound.

OK or NG

>> GO TO 8.

>> Perform trouble diagnosis for

EC-439

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.

4. Remove fuel injector gallery assembly. Refer to

EM-39, "Removal and Installation"

Keep fuel hose and all fuel injectors connected to fuel injector gallery.

The fuel injector harness connectors should remain connected.

At idling:

1.0 - 4.0 g/s

At 2,500 rpm:

4.0 - 12.0 g/s

At idling:

1.0 - 4.0 g/s

At 2,500 rpm:

4.0 - 12.0 g/s

Clicking noise should be heard.

PBIB1986E

EC-232

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0171 FUEL INJECTION SYSTEM FUNCTION

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

>> GO TO 9.

>> Replace fuel injectors from which fuel does not spray

out. Always replace O-ring with new ones.

CHECK INTERMITTENT INCIDENT

Perform

GI-42, "Intermittent Incident"

>> INSPECTION END

Fuel should be sprayed evenly for each fuel injector.

PBIB1726E

P0172 FUEL INJECTION SYSTEM FUNCTION

EC-233

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0172 FUEL INJECTION SYSTEM FUNCTION

On Board Diagnosis Logic

INFOID:0000000009480889

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:0000000009480890

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

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.

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-234, "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-234,

"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)

EC-234

< DTC/CIRCUIT DIAGNOSIS >

[QR25DE]

P0172 FUEL INJECTION SYSTEM FUNCTION

d. Check 1st trip DTC.
e. If 1st trip DTC is detected, go to

EC-234, "Diagnosis Procedure"

WITH GST

1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch OFF and wait at least 10 seconds.
3. Disconnect mass air flow sensor harness connector.
4. Restart engine and let it idle for at least 5 seconds.
5. Stop engine and reconnect mass air flow sensor harness con-

nector.

6. Select Service $03 with GST. Check that DTC P0102 is

detected.

7. Select Service $04 with GST and erase the DTC P0102.
8. Start engine.

If it is difficult to start engine, the fuel injection system has a mal-

function.

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-234, "Diagnosis Procedure"

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

9. Keep engine at idle for at least 5 minutes.
10. Check 1st trip DTC.
11. The 1st trip DTC P0172 should be detected at this stage, if a malfunction exists. If so, go to

EC-234,

"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.

d. Check 1st trip DTC.
e. If 1st trip DTC is detected, go to

EC-234, "Diagnosis Procedure"

Diagnosis Procedure