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EC
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P0171 FUEL INJECTION SYSTEM FUNCTION
DTC Logic INFOID:0000000004780135
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 f eedback signal from the A/F sensors 1. The ECM calcu-
lates the necessary compensation to correct the of fset between the actual and the theoretical ratios.
In case the amount of the compensation value is extrem ely large (The actual mixture ratio is too lean.), the
ECM judges the condition as the fuel injection system malfunction and lights up the MIL (2 trip detection logic).
DTC CONFIRMATION PROCEDURE MIXTURE RATIO SELF-LEARNING VALUE
CLEAR : Special Repair Requirement " .
2. Start engine.
Is it difficult to start engine? YES >> GO TO 3.
NO >> GO TO 4. YES >> Go to
EC-231, " Diagnosis Procedure " .
NO >> Check exhaust and intake air leak visually. YES >> Go to
EC-231, " Diagnosis Procedure " .
NO >> GO TO 5. 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 injectorDTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0171 Fuel injection system too
lean • Fuel injection system does not operate properly.
• The amount of mixture ratio compensation is too large. (The mixture ratio is too lean.) • Intake air leaks
• A/F sensor 1
• Fuel injector
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor
• Incorrect PCV hose connection
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YES >> Go to
EC-231, " Diagnosis Procedure " .
NO >> INSPECTION END VHCL SPEED SE 50 - 120 km/h (31 - 75 MPH)
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Wiring Diagram
INFOID:0000000004780683
Diagnosis Procedure INFOID:0000000004780136 B
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![NISSAN LATIO 2009 Service Repair Manual EC-232< COMPONENT DIAGNOSIS >
[HR16DE]
P0171 FUEL INJECTION SYSTEM FUNCTION
2. Listen for an exhaust gas leak before three way catalyst (manifold).
Is exhaust gas leak detected? YES >> Repair or repla NISSAN LATIO 2009 Service Repair Manual EC-232< COMPONENT DIAGNOSIS >
[HR16DE]
P0171 FUEL INJECTION SYSTEM FUNCTION
2. Listen for an exhaust gas leak before three way catalyst (manifold).
Is exhaust gas leak detected? YES >> Repair or repla](/manual-img/5/57359/w960_57359-1587.png)
EC-232< COMPONENT DIAGNOSIS >
[HR16DE]
P0171 FUEL INJECTION SYSTEM FUNCTION
2. Listen for an exhaust gas leak before three way catalyst (manifold).
Is exhaust gas leak detected? YES >> Repair or replace.
NO >> GO TO 2. 2.
CHECK FOR INTAKE AIR LEAK
1. Listen for an intake air leak after the mass air flow sensor.
2. Check PCV hose connection.
Intake air leak detected? YES >> Repair or replace.
NO >> GO TO 3. 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 the continuity between A/F sensor 1 harness connector and ECM harness connector.
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 or short to ground or short to power in harness or connectors. 4.
CHECK FUEL PRESSURE
1. Check fuel pressure. Refer to EC-498, " Inspection " .
Is the inspection result normal? YES >> GO TO 6. PBIB1216E
A/F sensor 1 ECM
Continuity
Connector Terminal Connector Terminal
F12 1
F11 49
Existed
2 53
A/F sensor 1 Ground Continuity
Connector Terminal
F12 1
Ground Not existed
2
ECM Ground Continuity
Connector Terminal
F11 49
Ground Not existed
53
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NO >> GO TO 5. YES >> Replace “fuel filter and fuel pump assembly”.
NO >> Repair or replace Mass Air Flow Sensor " .
With GST
1. Install all removed parts.
2. Check mass air flow sensor signal in Service $01 with GST.
3. For specification, refer to EC-504, " Mass Air Flow Sensor " .
Is the measurement value within the specification?YES >> GO TO 7.
NO >> Check connectors for rusted terminals or loose c onnections in the mass air flow sensor circuit or
grounds. Refer to EC-148, " DTC Logic " .
YES >> GO TO 8.
NO >> Perform trouble diagnosis for FUEL INJECTOR, refer to EC-430, " Component Function Check " .
Removal and Installation " .
Keep fuel hose and all fuel injectors connected to fuel tube.
5. Disconnect all ignition coil harness connectors.
6. Prepare pans or saucers under each fuel injector.
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YES >> GO TO 9.
NO >> Replace fuel injectors from which fuel does not spray out. Always replace O-ring with new ones. Diagnosis Procedure " .
>> INSPECTION END
Fuel should be sprayed even
ly for each fuel injector.
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EC
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P0172 FUEL INJECTION SYSTEM FUNCTION
DTC Logic INFOID:0000000004780137
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 f eedback signal from the A/F sensors 1. The ECM calcu-
lates the necessary compensation to correct the of fset between the actual and the theoretical ratios.
In case the amount of the compensation value is extrem ely 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 MIXTURE RATIO SELF-LEARNING VALUE
CLEAR : Special Repair Requirement " .
2. Start engine.
Is it difficult to start engine? YES >> GO TO 3.
NO >> GO TO 4. YES >> Go to
EC-237, " Diagnosis Procedure " .
NO >> Check exhaust and intake air leak visually. YES >> Go to
EC-237, " Diagnosis Procedure " .
NO >> GO TO 5. DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0172 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
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YES >> Go to
EC-237, " Diagnosis Procedure " .
NO >> INSPECTION END VHCL SPEED SE 50 - 120 km/h (31 - 75 MPH)