Infiniti QX56 (Z62). Manual — part 571
EC-262
< DTC/CIRCUIT DIAGNOSIS >
[VK56VD]
P0139, P0159 HO2S2
6.
REPLACE HEATED OXYGEN SENSOR 2
Replace malfunctioning heated oxygen sensor 2. Refer to
CAUTION:
• Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7
in) onto a hard surface such as a concrete floor; use a new one.
• Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread
Cleaner [commercial service tool (J-43897-18 or J-43897-12)] and approved anti-seize lubricant
(commercial service tool).
>> INSPECTION END
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-263
< DTC/CIRCUIT DIAGNOSIS >
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P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
DTC Logic
INFOID:0000000006217825
DTC DETECTION LOGIC
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 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 lean), the
ECM judges the condition as the fuel injection system malfunction and illuminates the MIL (2 trip detection
logic).
DTC CONFIRMATION PROCEDURE
1.
PRECONDITIONING
1.
Turn ignition switch OFF and wait at least 10 seconds.
2.
Turn ignition switch ON.
3.
Turn ignition switch OFF and wait at least 10 seconds.
>> GO TO 2.
2.
PERFORM DTC CONFIRMATION PROCEDURE-I
1.
Clear the mixture ratio self-learning value. Refer to
.
2.
Start engine.
Is it difficult to start engine?
YES
>> GO TO 3.
NO
>> GO TO 4.
3.
RESTART ENGINE
If it is difficult to start engine, the fuel injection system has a malfunction, too.
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.
Does engine start?
YES
>> Proceed to
.
NO
>> Check exhaust and intake air leakage visually.
4.
PERFORM DTC CONFIRMATION PROCEDURE-II
1.
Keep engine idle for at least 5 minutes.
2.
Check 1st trip DTC.
Is 1st trip DTC detected?
YES
>> Proceed to
.
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
(Trouble diagnosis content)
DTC detecting condition
Possible cause
P0171
FUEL SYS-LEAN-B1
[Fuel injection system too
lean (bank 1)]
• Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too
large. (The mixture ratio is too lean.)
• Intake air leakage
• A/F sensor 1
• Fuel injector
• Exhaust gas leakage
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor
• Incorrect PCV hose connection
P0174
FUEL SYS-LEAN-B2
[Fuel injection system too
lean (bank 2)]
EC-264
< DTC/CIRCUIT DIAGNOSIS >
[VK56VD]
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
NO
>> GO TO 5.
5.
PERFORM DTC CONFIRMATION PROCEDURE-III
1.
Turn ignition switch OFF and wait at least 10 seconds.
2.
Turn ignition switch ON.
3.
Turn ignition switch OFF and wait at least 10 seconds.
4.
Start engine.
5.
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.
6.
Check 1st trip DTC.
Is 1st trip DTC detected?
YES
>> Proceed to
.
NO
>> INSPECTION END
Diagnosis Procedure
INFOID:0000000006217826
1.
CHECK EXHAUST GAS LEAKAGE
1.
Start engine and run it at idle.
2.
Listen for an exhaust gas leakage before three way catalyst (manifold).
Is exhaust gas leakage detected?
YES
>> Repair or replace malfunctioning part.
NO
>> GO TO 2.
2.
CHECK FOR INTAKE AIR LEAKAGE
1.
Listen for an intake air leakage after the mass air flow sensor.
2.
Check PCV hose connection.
Is intake air leakage detected?
YES
>> Repair or replace malfunctioning part.
NO
>> GO TO 3.
3.
CHECK A/F SENSOR 1 CIRCUIT
1.
Turn ignition switch OFF.
2.
Disconnect corresponding A/F sensor 1 harness connector.
3.
Disconnect ECM harness connector.
4.
Check the continuity between A/F sensor 1 harness connector and ECM harness connector.
Vehicle speed
50 - 120 km/h (31 - 75 MPH)
PBIB1216E
P0171, P0174 FUEL INJECTION SYSTEM FUNCTION
EC-265
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5.
Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector
and ground.
6.
Also check harness for short to power.
Is the inspection result normal?
YES
>> GO TO 4.
NO
>> Repair open circuit, short to ground or short to power in harness or connectors.
4.
CHECK FUEL PRESSURE
Check fuel pressure. Refer to
Is the inspection result normal?
YES
>> GO TO 6.
NO
>> GO TO 5.
5.
DETECT MALFUNCTIONING PART
Check fuel hoses and fuel tubes for clogging.
Is the inspection result normal?
YES
>> Replace “fuel filter and fuel pump assembly”. Refer to
FL-5, "Removal and Installation"
.
NO
>> Repair or replace malfunctioning part.
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.
For specification, refer to
EC-538, "Mass Air Flow Sensor"
WITH GST
1.
Install all removed parts.
2.
Check mass air flow sensor signal in Service $01 with GST.
For specification, refer to
EC-538, "Mass Air Flow Sensor"
Is the measurement value within the specification?
YES
>> GO TO 7.
NO
>> Check connectors for rusted terminals or loose connections in the mass air flow sensor circuit or
grounds. Refer to
7.
CHECK FUNCTION OF FUEL INJECTOR
DTC
A/F sensor 1
ECM
Continuity
Bank
Connector
Terminal
Connector
Terminal
P0171
1
F67
3
F110
88
Existed
4
90
6
94
P0174
2
F68
3
78
4
80
6
74
DTC
A/F sensor 1
ECM
Continuity
Continuity
Bank
Connector
Terminal
Connector
Terminal
P0171
1
F67
3
F110
88
Existed
Not existed
4
90
6
94
P0174
2
F68
3
78
4
80
6
74
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