Infiniti Q45. Manual - part 422

DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION

EC-327

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9. 

CHECK FUNCTION OF FUEL INJECTOR-II

Provide battery voltage between the following terminals, and then
interrupt it. Listen to each fuel injector operating sound.

OK or NG

OK

>> GO TO 10.

NG

>> Perform trouble diagnosis for 

EC-706, "FUEL INJECTOR"

 .

10. 

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-32, "FUEL INJECTOR AND FUEL TUBE"

 .

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

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 11.

NG

>> Replace fuel injectors from which fuel does not spray

out. Always replace O-ring with new ones.

11. 

CHECK INTERMITTENT INCIDENT

Refer to 

EC-145, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

 .

>> INSPECTION END

Cylinder

Harness connector

terminal

(+)

(–)

1

F201

5

3

3

2

5

1

7

6

2

F221

5

3

4

2

6

1

8

6

Operating sound should exist.

PBIB2449E

Fuel should be sprayed evenly for each fuel injector.

PBIB1726E

EC-328

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

PFP:16600

On Board Diagnosis Logic

NBS001VA

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 air fuel ratio (A/F) sensor 1. The
ECM calculates 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

NBS001VB

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-II

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-II.

4.

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

5.

Select “DATA MONITOR” mode with CONSULT-II.

6.

Start engine again and let it idle for at least 10 minutes.
The 1st trip DTC P0172, P0175 should be detected at this stage,
if a malfunction exists. If so, go to 

EC-334, "Diagnostic Proce-

dure"

 .

NOTE:
If 1st trip DTC is not detected during above procedure, perform-
ing 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 a certain time. 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.

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.

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.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0172
0172
(Bank 1)

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.)

●

A/F sensor 1

●

Fuel injector

●

Exhaust gas leaks

●

Incorrect fuel pressure

●

Mass air flow sensor

P0175
0175
(Bank 2)

SEF968Y

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).

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

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If engine starts, go to 

EC-334, "Diagnostic Procedure"

 . If engine does not start, remove ignition plugs and

check for fouling, etc.

 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. Then
restart and run engine for at least 5 seconds at idle speed.

4.

Stop engine and reconnect mass air flow sensor harness con-
nector.

5.

Select Service $03 with GST. Make sure DTC P0102 is
detected. 

6.

Select Service $04 with GST and erase the DTC P0102.

7.

Start engine again and let it idle for at least 10 minutes.

8.

Select Service $07 with GST. The 1st trip DTC P0172 or P0175
should be detected at this stage, if a malfunction exists. If so, go
to 

EC-334, "Diagnostic 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 a certain
time. 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.

9.

If it is difficult to start engine at step 7, the fuel injection system has a malfunction.

10. Crank engine while depressing accelerator pedal.

If engine starts, go to 

EC-334, "Diagnostic Procedure"

 . If engine does not start, remove spark plugs and

check for fouling, etc.

PBIB2418E

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-330

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION

Wiring Diagram

NBS001VC

BANK 1

TBWM1228E