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Home >> Toyota >> 2019 >> Sienna SE, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 16 (Engine Control System [2GR-FE] - Diagnostic Codes (1 Of 3)) >> SFI System >> DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1); DTC P0174: System Too Lean (Bank 2); DTC P0175: System Too Rich (Bank 2) [12/2015 - 08/2016] >> Procedure

DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1); DTC P0174: System Too Lean (Bank 2); DTC P0175: System Too Rich (Bank 2) [12/2015 - 08/2016]: Procedure

WARNING: This page is about a different car, the 2016 Toyota Sienna. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Trouble Codes.
    5. Read DTCs.
      RESULT

      Result Proceed to
      DTC P0171, P0172, P0174 or P0175 is output A
      DTC P0171, P0172, P0174 or P0175 and other DTCs are output B

      HINT: 

      If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.

    Result: 

    B 

    GO TO DTC CHART 

    (Refer to DIAGNOSTIC TROUBLE CODE CHART [12/2015 - 08/2016] )

    Result: 

    A 

    See step  2

  2. CHECK PCV HOSE CONNECTIONS 
    1. Check the PCV hose connections (Refer to COMPONENTS [12/2015 - 08/2016] ).

      OK

      PCV valve and hose are connected correctly and are not damaged.

    Result: 

    NG 

    REPAIR OR REPLACE PCV HOSE 

    Result: 

    OK 

    See step  3

  3. CHECK INTAKE SYSTEM 
    1. Check the intake system for vacuum leaks.

      OK

      No leaks from intake system.

      HINT: 

      • If a malfunction occurs when depressing the brake pedal, inspect the brake booster assembly, as there may be a vacuum leak in the brake booster assembly itself.
      • Perform "Inspection After Repair" after replacing the intake system (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NG 

    REPAIR OR REPLACE INTAKE SYSTEM 

    Result: 

    OK 

    See step  4

  4. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) 
    1. Connect the Techstream to the DLC3.
    2. Start the engine.
    3. Turn the Techstream on.
    4. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
    5. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
    6. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
    7. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

      HINT: 

      • Perform the Active Test operation with the engine idling (press the -12.5% or 12.5% button to change the fuel injection volume).
      • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
      • 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.
      • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

      Standard Voltage

      Techstream Display (Sensor) Injection Volume Status Voltage
      AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio) 12.5% Rich Less than 3.1
      -12.5% Lean More than 3.4
      O2S B1S2 or O2S B2S2 (Heated oxygen) 12.5% Rich More than 0.55
      -12.5% Lean Less than 0.4
      RESULT

      Status AFS Voltage B1S1 or AFS Voltage B2S1 Status O2S B1S2 or O2S B2S2 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
      • PCV valve and hose
      • PCV hose connections
      • Fuel injector assembly blockage
      • Gas leak from exhaust system
      • Intake system
      • Fuel pressure
      • Mass air flow meter
      • Engine coolant temperature sensor
      		 A
      Rich Rich Actual air fuel ratio rich
      • Fuel injector assembly leak or blockage
      • Gas leak from exhaust system
      • Ignition system
      • Fuel pressure
      • Mass air flow meter
      • 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 Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1S1 or AFS Voltage B2S1) is consistently more than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2 or O2S B2S2) is consistently less than 0.4 V.

      Rich: During Control the Injection Volume for A/F Sensor, the AFS Voltage B1S1 or AFS Voltage B2S1 is consistently less than 3.1 V, and the O2S B1S2 or O2S B2S2 is consistently more than 0.55 V.

      Lean/Rich: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternates correctly.

      HINT: 

      Refer to "Data List / Active Test" [AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2] (Refer to DATA LIST / ACTIVE TEST [12/2015 - 08/2016] ).

    Result: 

    B 

    See step  11

    Result: 

    A 

    See step  5

  5. READ VALUE USING TECHSTREAM (COOLANT TEMP) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / Coolant Temp.
    5. Read the Coolant Temp twice, when the engine is both cold and warmed up.

      Standard

      Techstream Display Condition Specified Condition
      Coolant Temp Cold engine Same as ambient air temperature
      Warm engine Between 75 and 100°C (167 and 212°F)

      HINT: 

      Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NG 

    REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

    (Refer to REMOVAL [12/2015 - 08/2016] )

    Result: 

    OK 

    See step  6

  6. READ VALUE USING TECHSTREAM (MAF) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / MAF, Coolant Temp and Engine Speed.
    5. Read MAF with the engine speed at 3000 rpm.

      Standard

      Techstream Display Condition Specified Condition
      MAF Shift lever position: N (Neutral)
      A/C: Off
      Engine Speed: 3000 rpm      		 Between 11 gm/sec. and 16 gm/sec

    Result: 

    NG 

    See step  16

    Result: 

    OK 

    See step  7

  7. CHECK FUEL PRESSURE 
    1. Check the fuel pressure (Refer to PROCEDURE - Step 2 ).

    Result: 

    NG 

    REPAIR OR REPLACE FUEL SYSTEM 

    Result: 

    OK 

    See step  8

  8. CHECK FOR EXHAUST GAS LEAK 
    1. Check for exhaust gas leaks.

      OK

      No exhaust gas leaks.

      HINT: 

      Perform "Inspection After Repair" after replacing the exhaust system (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NG 

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

    Result: 

    OK 

    See step  9

  9. CHECK FOR SPARKS AND IGNITION 
    1. Perform a spark test.

      HINT: 

      • Refer to the ignition system inspection procedure (Refer to ON-VEHICLE INSPECTION [12/2015 - 08/2016] ).
      • If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Cylinder #1 Misfire Count (to Cylinder #6 Misfire Count).
      • Perform "Inspection After Repair" after repairing or replacing the ignition system (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NG 

    REPAIR OR REPLACE IGNITION SYSTEM 

    Result: 

    OK 

    See step  10

  10. INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME) 
    1. Check the injection and volume.

      HINT: 

      • Refer to the fuel injector assembly inspection procedure (Refer to PROCEDURE - Step 1 ).
      • If the injectors malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine / Data List / Cylinder #1 Misfire Count (to Cylinder #6 Misfire Count).
      • Perform "Inspection After Repair" after replacing the fuel injector assembly (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    OK 

    See step  15

    Result: 

    NG 

    REPLACE FUEL INJECTOR ASSEMBLY 

    (Refer to REMOVAL [12/2015 - 08/2016] )

  11. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) 
    1. Inspect the air fuel ratio sensor (Refer to PROCEDURE - Step 1 ).

    Result: 

    NG 

    REPLACE AIR FUEL RATIO SENSOR 

    (Refer to REMOVAL [12/2015 - 08/2016] )

    Result: 

    OK 

    See step  12

  12. CHECK TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR) 
    GTY704398Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Disconnect the air fuel ratio sensor connectors.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      B14-2 (+B) - Body ground Ignition switch ON 11 to 14 V
      B13-2 (+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)
      *b for Bank 1
      *c for Bank 2

    Result: 

    NG 

    See step  21

    Result: 

    OK 

    See step  13

  13. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM) 
    1. Disconnect the B13 and B14 air fuel ratio sensor connectors.
    2. Disconnect the B1 ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B14-1 (HA1A) - B1-22 (HA1A) Always Below 1 Ω
      B14-3 (A1A+) - B1-126 (A1A+) Always Below 1 Ω
      B14-4 (A1A-) - B1-125 (A1A-) Always Below 1 Ω
      B13-1 (HA2A) - B1-20 (HA2A) Always Below 1 Ω
      B13-3 (A2A+) - B1-103 (A2A+) Always Below 1 Ω
      B13-4 (A2A-) - B1-102 (A2A-) Always Below 1 Ω
      B14-1 (HA1A) or B1-22 (HA1A) - Body ground Always 10 kΩ or higher
      B14-3 (A1A+) or B1-126 (A1A+) - Body ground Always 10 kΩ or higher
      B14-4 (A1A-) or B1-125 (A1A-) - Body ground Always 10 kΩ or higher
      B13-1 (HA2A) or B1-20 (HA2A) - Body ground Always 10 kΩ or higher
      B13-3 (A2A+) or B1-103 (A2A+) - Body ground Always 10 kΩ or higher
      B13-4 (A2A-) or B1-102 (A2A-) - Body ground Always 10 kΩ or higher

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  14

  14. REPLACE AIR FUEL RATIO SENSOR 
    1. Replace the air fuel ratio sensor (Refer to REMOVAL [12/2015 - 08/2016] ).

      HINT: 

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NEXT 

    See step  15

  15. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear DTCs (Refer to DTC CHECK / CLEAR [12/2015 - 08/2016] ).
    5. Turn the ignition switch off and wait for at least 30 seconds.
    6. Turn the ignition switch to ON.
    7. Turn the Techstream on.
    8. Start the engine and warm it up.
    9. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
    10. Enter the following menus: Powertrain / Engine / Trouble Codes.
    11. Read the pending DTCs.
      RESULT

      Result Proceed to
      DTC P0171, P0172, P0174 or P0175 is output A
      DTC is not output B

    Result: 

    B 

    END 

    Result: 

    A 

    See step  16

  16. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER CONNECTOR CONNECTION) 
    1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and ECM (Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [12/2015 - ] ).

      HINT: 

      Repair any problems.

    Result: 

    NEXT 

    See step  17

  17. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear DTCs (Refer to DTC CHECK / CLEAR [12/2015 - 08/2016] ).
    5. Turn the ignition switch off and wait for at least 30 seconds.
    6. Turn the ignition switch to ON.
    7. Turn the Techstream on.
    8. Start the engine and warm it up.
    9. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
    10. Enter the following menus: Powertrain / Engine / Trouble Codes.
    11. Read the pending DTCs.
      RESULT

      Result Proceed to
      DTC P0171, P0172, P0174 or P0175 is output A
      DTC is not output B

    Result: 

    B 

    END 

    Result: 

    A 

    See step  18

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

    See step  6

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  19

  19. REPLACE MASS AIR FLOW METER 
    1. Replace the mass air flow meter (Refer to REMOVAL [12/2015 - 08/2016] ).

      HINT: 

      • 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.
      • Perform "Inspection After Repair" after replacing the mass air flow meter (Refer to INITIALIZATION [12/2015 - 08/2016] ).

    Result: 

    NEXT 

    See step  20

  20. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear DTCs (Refer to DTC CHECK / CLEAR [12/2015 - 08/2016] ).
    5. Turn the ignition switch off and wait for at least 30 seconds.
    6. Turn the ignition switch to ON.
    7. Turn the Techstream on.
    8. Start the engine and warm it up.
    9. Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
    10. Enter the following menus: Powertrain / Engine / Trouble Codes.
    11. Read the pending DTCs.
      RESULT

      Result Proceed to
      DTC is not output A
      DTC P0171, P0172, P0174 or P0175 is output B

    Result: 

    A 

    END 

    Result: 

    B 

    REPLACE ECM 

    (Refer to REMOVAL [12/2015 - 08/2016] )

  21. CHECK HARNESS AND CONNECTOR (A/F HTR RELAY - AIR FUEL RATIO SENSOR) 
    1. Disconnect the B13 and B14 air fuel ratio sensor connectors.
    2. Remove the A/F HTR relay from the engine room relay block.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      B14-2 (+B) - 3 (A/F HTR relay holder) Always Below 1 Ω
      B13-2 (+B) - 3 (A/F HTR relay holder) Always Below 1 Ω
      B14-2 (+B) or 3 (A/F HTR relay holder) - Body ground Always 10 kΩ or higher
      B13-2 (+B) or 3 (A/F HTR relay holder) - Body ground Always 10 kΩ or higher

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  22

  22. INSPECT A/F HTR RELAY 
    GTY690881Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    1. Remove the A/F HTR relay from the engine room relay block.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3 - 5 Battery voltage not applied 10 kΩ or higher
      Battery voltage applied to terminals 1 and 2 Below 1 Ω

    Result: 

    OK 

    CHECK ECM POWER SOURCE CIRCUIT 

    (Refer to ECM Power Source Circuit [12/2015 - 08/2016] )

    Result: 

    NG 

    REPLACE A/F HTR RELAY 

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