Nissan Titan. Manual - part 235

P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-241

< DTC/CIRCUIT DIAGNOSIS >

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7. If it is difficult to start engine at step 6, the fuel injection system has a malfunction, too.
8. Crank engine while depressing accelerator pedal. If engine starts, go to 

EC-241, "Diagnosis Procedure"

. If

engine does not start, check exhaust and intake air leak visually.

 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. Make sure DTC P0102 is

detected.

7. Select Service $04 with GST and erase the DTC P0102.
8. Start engine again and let it idle for at least 10 minutes.
9. Select Service $07 with GST. The 1st trip DTC P0171 or P0174

should be detected at this stage, if a malfunction exists. If so, go

to 

EC-241, "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 and drive the vehicle under the similar conditions to (1st trip) Freeze Frame Data for 10 min-

utes. Refer to the table below.

Hold the accelerator pedal as steady as possible.

The similar conditions to (1st trip) Freeze Frame Data means the vehicle operation that the following con-

ditions should be satisfied at the same time.

10. If it is difficult to start engine at step 8, the fuel injection system has a malfunction.
11. Crank engine while depressing accelerator pedal. If engine starts, go to 

EC-241, "Diagnosis Procedure"

.

If engine does not start, check exhaust and intake air leak visually.

Diagnosis Procedure

INFOID:0000000009886651

1.

CHECK EXHAUST GAS LEAK

1. Start engine and run it at idle.

Engine coolant temperature (T) 
condition

When the freeze frame data shows lower than 70 

°C (158 °F),

T should be lower than 70 

°C (158 °F).

When the freeze frame data shows higher than or equal to 70 

°C (158 °F),

T should be higher than or equal to 70 

°C (158 °F).

BBIA0368E

Engine speed

Engine speed in the freeze frame data 

± 400 rpm

Vehicle speed

Vehicle speed in the freeze frame data 

± 10 km/h (6 MPH)

Engine coolant temperature (T) 
condition

When the freeze frame data shows lower than 70 

°C (158 °F),

T should be lower than 70 

°C (158 °F).

When the freeze frame data shows higher than or equal to 70 

°C (158 °F),

T should be higher than or equal to 70 

°C (158 °F).

EC-242

< DTC/CIRCUIT DIAGNOSIS >

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

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 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 harness continuity between the following terminals.

Refer to Wiring Diagram.

5. Check harness continuity between the following terminals and ground.

Refer to Wiring Diagram.

PBIB1216E

A/F sensor 1 terminal

ECM terminal

Bank 1

1

35

2

56

Bank 2

1

16

2

75

Continuity should exist.

Bank 1

Bank 2

A/F sensor 1 terminal

ECM terminal

A/F sensor 1 terminal

ECM terminal

1

35

1

16

2

56

2

75

Continuity should not exist.

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-243

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6. Also check harness for short to power.
OK or NG

OK

>> GO TO 4.

NG

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

4.

CHECK FUEL PRESSURE

1. Release fuel pressure to zero. Refer to 

EC-489, "Fuel Pressure Check"

.

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

EC-489, "Fuel Pressure

Check"

.

OK or NG

OK

>> GO TO 6.

NG

>> GO TO 5.

5.

DETECT MALFUNCTIONING PART

Check the following.

• Fuel pump and circuit (Refer to 

EC-462

.)

• <Flexible Fuel Vehicle>

FPCM and circuit (Refer to 

EC-381

.)

• Fuel pressure regulator (Refer to 

EC-489, "Fuel Pressure Check"

.)

• Fuel lines

• Fuel filter for clogging

>> Repair or replace.

6.

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

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-172

.

7.

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.

At idling: Approximately 350 kPa (3.57 kg/cm

2

, 51 psi)

3.0 - 9.0 g/s

: at idling

9.0 - 28.0 g/s

: at 2,500 rpm

3.0 - 9.0 g/s

: at idling

97.0 - 28.0 g/s

: at 2,500 rpm

EC-244

< DTC/CIRCUIT DIAGNOSIS >

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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

2. Listen to each fuel injector operating sound.

OK or NG

OK

>> GO TO 8.

NG

>> Perform trouble diagnosis for FUEL INJECTOR, refer to

EC-459

.

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 all fuel injector harness connectors.

4. Remove fuel injector gallery assembly. Refer to 

EM-43, "Removal and Installation"

.

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

5. For DTC P0171, reconnect fuel injector harness connectors on bank 1.

For DTC P0174, reconnect fuel injector harness connectors on bank 2.

6. Disconnect all ignition coil harness connectors.

7. Prepare pans or saucers under each fuel injector.

8. Crank engine for about 3 seconds.

For DTC P0171, make sure that fuel sprays out from fuel injec-

tors on bank 1.

For DTC P0174, make sure that fuel sprays out from fuel injec-

tors on bank 2.

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

Refer to 

GI-39, "How to Check Terminal"

 and 

GI-42, "Intermittent Incident"

.

>> INSPECTION END

Clicking noise should be heard.

PBIB1986E

Fuel should be sprayed evenly for each fuel injector.

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