2007 INFINITI QX56 Factory Service Manual

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Page 1377 of 3061

INFINITI QX56 2007 Factory Service Manual EC-294
< SERVICE INFORMATION >
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
Wiring Diagram
INFOID:0000000003531794
BANK 1
Specification data are reference values and are measured between each termi

Page 1378 of 3061

INFINITI QX56 2007 Factory Service Manual DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-295
< SERVICE INFORMATION >
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Do not use ECM ground terminals when measuring input/output voltage. Doing so may result

Page 1379 of 3061

INFINITI QX56 2007 Factory Service Manual EC-296
< SERVICE INFORMATION >
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
BANK 2
Specification data are reference values and are measured between each terminal and ground.
Pulse signal is measure

Page 1380 of 3061

INFINITI QX56 2007 Factory Service Manual DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-297
< SERVICE INFORMATION >
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: Average voltage for pulse signal (Actual pulse signal can be confirmed by oscilloscope.

Page 1381 of 3061

INFINITI QX56 2007 Factory Service Manual EC-298
< SERVICE INFORMATION >
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
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

Page 1382 of 3061

INFINITI QX56 2007 Factory Service Manual DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-299
< SERVICE INFORMATION >
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• Fuel pump and circuit (Refer to EC-613.)
• Fuel pressure regulator (Refer to EC-80,

Page 1383 of 3061

INFINITI QX56 2007 Factory Service Manual EC-300
< SERVICE INFORMATION >
DTC P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
3. Disconnect all fuel injector harness connectors.
4. Remove fuel injector gallery assembly. Refer to EM-31
.
Keep fuel

Page 1384 of 3061

INFINITI QX56 2007 Factory Service Manual DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
EC-301
< SERVICE INFORMATION >
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DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
On Board Diagnosis LogicINFOID:0000000003

DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
EC-301
< SERVICE INFORMATION >
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DTC P0172, P0175 FUEL INJECTION SYSTEM FUNCTION
On Board Diagnosis LogicINFOID:0000000003531796
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 sensors 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 ProcedureINFOID:0000000003531797
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-306, "
Diagnosis 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 10 minutes. 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.
Sensor Input signal to ECM ECM function Actuator
A/F sensor 1Density 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)
conditionWhen 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).

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