Dtc P0171 System Too Lean (Bank 1)


DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)

CHECK PCV HOSE CONNECTIONS

CHECK INTAKE SYSTEM

PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

READ VALUE USING GTS (COOLANT TEMP)

READ VALUE USING GTS (MAF)

CHECK FUEL PRESSURE

CHECK FOR EXHAUST GAS LEAK

CHECK FOR SPARKS AND IGNITION

INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

REPLACE AIR FUEL RATIO SENSOR

PERFORM CONFIRMATION DRIVING PATTERN

CHECK HARNESS AND CONNECTOR

CHECK WHETHER DTC OUTPUT RECURS

CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM)

REPLACE MASS AIR FLOW METER SUB-ASSEMBLY

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - AIR FUEL RATIO SENSOR, BODY GROUND)

INSPECT NO. 1 INTEGRATION RELAY (A/F)

DTC P0171 System Too Lean (Bank 1)

DTC P0172 System Too Rich (Bank 1)


DESCRIPTION

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and long-term fuel trims.
The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at stoichiometric levels. The signal from the air fuel ratio sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel ratio is rich and an increase in the fuel injection volume if it is lean.
Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation.

DTC No.
DTC Detection Condition
Trouble Area
P0171
With a warm engine and stable air-fuel ratio feedback, the fuel trim is considerably in error to the lean side (2 trip detection logic).
  1. Intake system
  2. Fuel injector blockage
  3. Mass air flow meter sub-assembly
  4. Engine coolant temperature sensor
  5. Fuel pressure
  6. Gas leak from exhaust system
  7. Open or short in air fuel ratio sensor (Sensor 1) circuit
  8. Air fuel ratio sensor (Sensor 1)
  9. Air fuel ratio sensor heater (Sensor 1)
  10. No. 1 integration relay
  11. Air fuel ratio sensor heater circuit
  12. PCV valve and hose
  13. PCV hose connections
  14. ECM
  15. Wire harness or connector
P0172
With a warm engine and stable air-fuel ratio feedback, the fuel trim is considerably in error to the rich side (2 trip detection logic).
  1. Fuel injector leakage or blockage
  2. Mass air flow meter sub-assembly
  3. Engine coolant temperature sensor
  4. Ignition system
  5. Fuel pressure
  6. Gas leak from exhaust system
  7. Open or short in air fuel ratio sensor (Sensor 1) circuit
  8. Air fuel ratio sensor (Sensor 1)
  9. Air fuel ratio sensor heater (Sensor 1)
  10. No. 1 integration relay
  11. Air fuel ratio sensor heater circuit
  12. ECM
  13. Wire harness or connector
HINT:
  1. When DTC P0171 is stored, the actual air-fuel ratio is on the lean side. When DTC P0172 is stored, the actual air-fuel ratio is on the rich side.
  2. If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 may be stored. The MIL is then illuminated.
  3. When the total of the short-term and long-term fuel trim values is within the malfunction threshold (and the engine coolant temperature is higher than 75°C [167°F]), the system is functioning normally.

MONITOR DESCRIPTION

Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ECM cause changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim values. Deviations from the ECM estimated fuel injection volumes also affect the average fuel trim learned value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learned value of the air-fuel ratio). If the average fuel trim learned value exceeds the malfunction threshold, the ECM interprets this as a fault in the fuel system and stores a DTC.
Example:
If the average fuel trim learned value is +48% or more, or -38% or less, the ECM interprets this as a fuel system malfunction.

Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.2Tr-Fe Engine Control.Sfi System. Dtc P0171 System Too Lean (Bank 1)


MONITOR STRATEGY


Required Sensors/Components
Air fuel ratio sensor, Mass air flow meter sub-assembly, Crankshaft position sensor
Frequency of Operation
Continuous

TYPICAL ENABLING CONDITIONS


Fuel system status
Closed loop
Battery voltage
11 V or higher
Either of following conditions 1 or 2 met
-
1. Engine speed
Less than 650 rpm
2. Engine load
11.3% or more

TYPICAL MALFUNCTION THRESHOLDS


Purge-cut
Executing
Either of following conditions 1 or 2 met
-
1. Average of short-term fuel trim and long-term fuel trim
48% or more (varies with engine coolant temperature)
2. Average of short-term fuel trim and long-term fuel trim
-38% or less (varies with engine coolant temperature)

CONFIRMATION DRIVING PATTERN


Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.2Tr-Fe Engine Control.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Connect the GTS to the DLC3.
  2. Turn the ignition switch to ON and turn the GTS on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).
  4. Turn the ignition switch off and wait for at least 30 seconds.
  5. Turn the ignition switch to ON and turn the GTS on [A].
  6. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher with all the accessories switched off [B].
  7. With the engine warmed up, idle the engine for 2 minutes or more [C].
  8. Drive the vehicle at a speed between 60 and 100 km/h (38 and 63 mph) for 5 minutes or more [D].
    CAUTION:
    When performing the confirmation driving pattern, obey all speed limits and traffic laws.
  9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
  10. Read the pending DTCs.
    HINT:
    If a pending DTC is output, the system is malfunctioning.

WIRING DIAGRAM

Refer to DTC P0102 (LandCruiser RM000000U5B0U9X.html).
Refer to DTC P2195 (LandCruiser RM000000WC40YKX_07.html).

INSPECTION PROCEDURE

HINT:
  1. Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
  2. A low air fuel ratio sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
  3. A high air fuel ratio sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
  4. Sensor 1 refers to the sensor closest to the engine assembly.
  5. Sensor 2 refers to the sensor farthest away from the engine assembly.
1.CHECK FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  1. Read the DTCs.

    Result
    Result
    		Proceed to
    P0171 or P0172 is output
    		A
    P0171 or P0172 and other DTCs are output
    		B
    HINT:
    If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.


B
GO TO DTC CHART (LandCruiser RM000000VNN00FX.html)
A


2.CHECK PCV HOSE CONNECTIONS

  1. Check the PCV hose connections (LandCruiser RM00000141J019X_01_0001.html).

    OK:
    PCV hose is connected correctly and is not damaged.


NG
REPAIR OR REPLACE PCV HOSE
OK


3.CHECK INTAKE SYSTEM

  1. Check the intake system for vacuum leaks.

    OK:
    No leaks in intake system.
    HINT:
    1. If a malfunction is detected while the brake pedal is being depressed, vacuum leaks in the brake booster are suspected. Inspect the brake booster.
    2. Perform "Inspection After Repair" after repairing or replacing the intake system (LandCruiser RM000004NJC03XX.html).


NG
REPAIR OR REPLACE INTAKE SYSTEM
OK


4.PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)

  1. Connect the GTS to the DLC3.

  1. Start the engine.

  1. Turn the GTS on.

  1. Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.

  1. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

  1. Perform the Control the Injection Volume for A/F Sensor operation with the engine idling.

  1. Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the GTS.

    HINT:
    1. Change the fuel injection volume within the range of -12.5% to +12.5%.
    2. The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
    3. If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

    GTS Display (Sensor)
    		Injection Volume
    		Status
    		Voltage
    AFS Voltage B1S1
    (Air fuel ratio)
    		+12.5%
    		Rich
    		Below 3.1 V
    AFS Voltage B1S1
    (Air fuel ratio)
    		-12.5%
    		Lean
    		Higher than 3.4 V
    O2S B1S2
    (Heated oxygen)
    		+12.5%
    		Rich
    		Higher than 0.55 V
    O2S B1S2
    (Heated oxygen)
    		-12.5%
    		Lean
    		Below 0.4 V

    Result
    Status of AFS Voltage B1S1
    		Status of O2S B1S2
    		Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition
    		Suspected Trouble Area
    		Proceed to
    Lean/Rich
    		Lean/Rich
    		Normal
    		-
    		A
    Lean
    		Lean
    		Actual air fuel ratio lean
    1. PCV valve and hose
    2. PCV hose connections
    3. Fuel injector blockage
    4. Gas leaks from exhaust system
    5. Intake system
    6. Fuel pressure
    7. Mass air flow meter sub-assembly
    8. Engine coolant temperature sensor
    		A
    Rich
    		Rich
    		Actual air fuel ratio rich
    1. Fuel injector leakage or blockage
    2. Gas leaks from exhaust system
    3. Ignition system
    4. Fuel pressure
    5. Mass air flow meter sub-assembly
    6. Engine coolant temperature sensor
    		A
    Lean
    		Lean/Rich
    		Air fuel ratio sensor malfunction
    		Air fuel ratio sensor
    		B
    Rich
    		Lean/Rich
    		Air fuel ratio sensor malfunction
    		Air fuel ratio sensor
    		B
    Lean: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.
    Rich: During the Control the Injection Volume for A/F Sensor Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.
    Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output voltage of the heated oxygen sensor alternates correctly.


B
Go to step 11
A


5.READ VALUE USING GTS (COOLANT TEMP)

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.

  1. Read Coolant Temp twice, when the engine is both cold and warmed up.

    Standard:
    With cold engine: Same as ambient air temperature.
    With warm engine: Between 75°C and 100°C (167°F and 212°F).
    HINT:
    Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (LandCruiser RM000004NJC03XX.html).


NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR (LandCruiser RM00000111M00LX.html)
OK


6.READ VALUE USING GTS (MAF)

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF and Coolant Temp.

  1. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.

  1. Read MAF with the engine speed at 3000 rpm.

    Standard:
    Between 6.0 gm/sec and 18.0 gm/sec (shift lever: N; A/C: Off).


NG
Go to step 16
OK


7.CHECK FUEL PRESSURE

  1. Check the fuel pressure (LandCruiser RM000000Q3M06EX_01_0002.html).



NG
REPAIR OR REPLACE FUEL SYSTEM
OK


8.CHECK FOR EXHAUST GAS LEAK

  1. Check for exhaust gas leaks.

    OK:
    No gas leaks.
    HINT:
    Perform "Inspection After Repair" after repairing or replacing the exhaust system (LandCruiser RM000004NJC03XX.html).


NG
REPAIR OR REPLACE EXHAUST SYSTEM
OK


9.CHECK FOR SPARKS AND IGNITION

  1. Check the ignition system (LandCruiser RM000000SM6077X.html).

    HINT:
    Perform "Inspection After Repair" after repairing or replacing the ignition system (LandCruiser RM000004NJC03XX.html).


NG
REPAIR OR REPLACE IGNITION SYSTEM
OK


10.INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)

  1. Inspect the fuel injector assembly (injection and volume) (LandCruiser RM000000WQQ0BIX.html).

    HINT:
    1. If the fuel injector assemblies malfunction, engine misfire may occur. The misfire count can be read using the GTS. Enter the following menus: Powertrain / Engine an ECT / Data List / Ptrl Misfire / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
    2. Perform "Inspection After Repair" after replacing the fuel injector assembly (LandCruiser RM000004NJC03XX.html).


OK
Go to step 15

NG
REPLACE FUEL INJECTOR ASSEMBLY (LandCruiser RM000000Q480CIX.html)

11.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

  1. Inspect the air fuel ratio sensor (LandCruiser RM00000175800NX.html).

    HINT:
    Perform "Inspection After Repair" after replacing the air fuel ratio sensor (LandCruiser RM000004NJC03XX.html).


NG
REPLACE AIR FUEL RATIO SENSOR (LandCruiser RM00000175900NX.html)
OK


12.CHECK TERMINAL VOLTAGE (+B OF AIR FUEL RATIO SENSOR)
Land Cruiser, Land Cruiser Prado. Grj150 Trj150,155 Kdj150,155 Lj150, Gdj150,155.2Tr-Fe Engine Control.Sfi System. Dtc P0171 System Too Lean (Bank 1)

  1. Disconnect the air fuel ratio sensor connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage according to the value(s) in the table below.

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    C56-2 (+B) - Body ground
    		Ignition switch ON
    		11 to 14 V
    Text in Illustration
    *a
    		Front view of wire harness connector
    (to Air Fuel Ratio Sensor)


NG
Go to step 21
OK


13.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

  1. Disconnect the air fuel ratio sensor connector.

  1. Disconnect the ECM connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:

    Tester Connection
    		Condition
    		Specified Condition
    C56-1 (HA1A) - C154-6 (HA1A)
    		Always
    		Below 1 Ω
    C56-1 (HA1A) or C154-6 (HA1A) - Body ground
    		Always
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


14.REPLACE AIR FUEL RATIO SENSOR

  1. Replace the air fuel ratio sensor (LandCruiser RM00000175900NX.html).

    HINT:
    Perform "Inspection After Repair" after replacing the air fuel ratio sensor (LandCruiser RM000004NJC03XX.html).

NEXT


15.PERFORM CONFIRMATION DRIVING PATTERN

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Clear the DTCs (LandCruiser RM000000VNG00DX.html).

  1. Turn the ignition switch off and wait for at least 30 seconds.

  1. Start the engine and warm it up.

  1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

  1. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  1. Read the DTCs.

    Result
    Result
    		Proceed to
    DTC P0171 or P0172 is output
    		A
    DTC is not output
    		B


B
END
A


16.CHECK HARNESS AND CONNECTOR

  1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM (LandCruiser RM000003YMI00MX.html).

    HINT:
    Repair any problems.

NEXT


17.CHECK WHETHER DTC OUTPUT RECURS

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Clear the DTCs (LandCruiser RM000000VNG00DX.html).

  1. Turn the ignition switch off and wait for at least 30 seconds.

  1. Start the engine and warm it up.

  1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

  1. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  1. Read the DTCs.

    Result
    Result
    		Proceed to
    DTC P0171 or P0172 is output
    		A
    DTC is not output
    		B


B
END
A


18.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM)

  1. Disconnect the mass air flow meter sub-assembly connector.

  1. Disconnect the ECM connector.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:

    Tester Connection
    		Condition
    		Specified Condition
    C33-3 (VG) - C154-24 (VG)
    		Always
    		Below 1 Ω
    C33-2 (E2G) - C154-32 (E2G)
    		Always
    		Below 1 Ω
    C33-3 (VG) or C154-24 (VG) - Body ground
    		Always
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


19.REPLACE MASS AIR FLOW METER SUB-ASSEMBLY

  1. Replace the mass air flow meter sub-assembly (LandCruiser RM000002VE200IX.html).

    HINT:
    1. If the result of the inspection performed in step 6 indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
    2. Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly(LandCruiser RM000004NJC03XX.html).

NEXT


20.CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

  1. Connect the GTS to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the GTS on.

  1. Clear the DTCs (LandCruiser RM000000VNG00DX.html).

  1. Turn the ignition switch off and wait for at least 30 seconds.

  1. Start the engine and warm it up.

  1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

  1. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  1. Read the DTCs.

    Result
    Result
    		Proceed to
    DTC is not output
    		A
    DTC P0171 or P0172 is output
    		B


B
REPLACE ECM (LandCruiser RM000000VW203EX.html)
A

END

21.CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - AIR FUEL RATIO SENSOR, BODY GROUND)

  1. Disconnect the air fuel ratio sensor connector.

  1. Remove the No. 1 integration relay from the engine room relay block.

  1. Measure the resistance according to the value(s) in the table below.

    Standard Resistance:

    Tester Connection
    		Condition
    		Specified Condition
    1B-8 - C56-2 (+B)
    		Always
    		Below 1 Ω
    1B-7 - Body ground
    		Always
    		Below 1 Ω
    1B-8 or C56-2 (+B) - Body ground
    		Always
    		10 kΩ or higher


NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


22.INSPECT NO. 1 INTEGRATION RELAY (A/F)

  1. Inspect the No. 1 integration relay (A/F) (LandCruiser RM000003BLB03PX_01_0015.html).



NG
REPLACE NO. 1 INTEGRATION RELAY
OK

CHECK ECM POWER SOURCE CIRCUIT (LandCruiser RM0000027690EIX.html)