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Home >> Toyota >> 2024 >> Corolla LE >> Repair and Diagnosis >> External Pages >> Different car >> Section 258 (Engine Control System (2ZR-FAE) - Diagnostic Codes (3 Of 8)) >> SFI System >> DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1) [01/2019 - 03/2019] >> Procedure

DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1) [01/2019 - 03/2019]: Procedure

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  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172) 
    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 and ECT / Trouble Codes.
    5. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      Result

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

      HINT: 

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

    Result: 

    B 

    GO TO DTC CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [01/2019 - 03/2019] 

    Result: 

    A 

    See step  2

  2. CHECK PCV HOSE CONNECTIONS 
    1. Check the PCV hose connections.

      Refer to COMPONENTS [01/2019 - 11/2022]

      OK

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

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE PCV HOSE 

    Result: 

    OK 

    See step  3

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

      Refer to ON-VEHICLE INSPECTION [01/2019 - 11/2022]

      OK

      No leaks in intake system.

      HINT: 

      Perform "Inspection After Repair" after repairing or replacing the intake system.

      Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    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 and run the engine at an engine speed of 2500 rpm for 90 seconds.
    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / Coolant Temp, AFS Voltage B1S1 and O2S B1S2.

      Powertrain > Engine and ECT > Active Test 

      Active Test Display
      Control the Injection Volume for A/F Sensor
      Data List Display
      Coolant Temp
      AFS Voltage B1S1
      O2S B1S2
    6. Change the fuel injection volume using the Techstream, and monitor the output voltage of the air fuel ratio sensor (AFS Voltage B1S1) and heated oxygen sensor (O2S B1S2) displayed on the Techstream.

      HINT: 

      • The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.
      • 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

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

      Result

      Status AFS Voltage B1S1 Status 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
      • PCV valve and hose
      • PCV hose connections
      • Fuel injector assembly blockage
      • Gas leak from exhaust system
      • Intake system
      • Fuel pressure
      • Mass air flow meter sub-assembly
      • Engine coolant temperature sensor
      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 sub-assembly
      • Engine coolant temperature sensor
      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
      1. Lean: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
      2. Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently below 3.1 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently higher than 0.55 V.
      3. Lean/Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the output voltage of the fuel ratio sensor (AFS Voltage B1S1) or heated oxygen sensor (O2S B1S2) alternates correctly.

      HINT: 

      Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2].

      Refer to DATA LIST / ACTIVE TEST [01/2019 - 03/2019]

    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 and ECT / Data List / Coolant Temp.

      Powertrain > Engine and ECT > Data List 

      Tester Display
      Coolant Temp
    5. Read the Data List 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 [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE ENGINE COOLANT TEMPERATURE SENSOR. Refer to  REMOVAL [01/2019 - 03/2019] 

    Result: 

    OK 

    See step  6

  6. READ VALUE USING TECHSTREAM (MAF) 
    1. Connect the Techstream to the DLC3.
    2. Start the engine.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF, Coolant Temp and Engine Speed.

      Powertrain > Engine and ECT > Data List 

      Tester Display
      Engine Speed
      MAF
      Coolant Temp
    5. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
    6. Read MAF with the engine speed at 3000 rpm.

      Standard

      Techstream Display Condition Specified Condition
      MAF
      • Engine warmed up
      • Shift lever position: N (neutral)
      • A/C: Off
      • Engine Speed: 3000 rpm
      		 Between 5.0 and 10.0 gm/sec

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  18

    Result: 

    OK 

    See step  7

  7. CHECK FUEL PRESSURE 
    1. Check the fuel pressure.

      Refer to PROCEDURE - Step 2

      Result

      Proceed to
      OK
      NG

    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 gas leaks in exhaust system.

      HINT: 

      Perform "Inspection After Repair" after repairing or replacing the exhaust system.

      Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE EXHAUST SYSTEM 

    Result: 

    OK 

    See step  9

  9. INSPECT IGNITION SYSTEM 
    1. Inspect the ignition system.

      Refer to ON-VEHICLE INSPECTION [01/2019 - 11/2022]

      HINT: 

      • 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 and ECT / Data List / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
      • Perform "Inspection After Repair" after repairing or replacing the ignition system.

        Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    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 INSPECTION [01/2019 - 11/2022]

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

        Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    See step  16

    Result: 

    NG 

    REPLACE FUEL INJECTOR ASSEMBLY. Refer to  REMOVAL [01/2019 - 03/2019] 

  11. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) 
    1. Inspect the air fuel ratio sensor.

      Refer to INSPECTION [01/2019 - 11/2022]

      HINT: 

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor.

      Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE AIR FUEL RATIO SENSOR. Refer to  REMOVAL [01/2019 - 11/2022] 

    Result: 

    OK 

    See step  12

  12. CHECK TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR) 
    1. Disconnect the air fuel ratio sensor connector.
      GTY910714Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Air Fuel Ratio Sensor)
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      C55-2 (+B) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - EFI-MAIN RELAY) 

    Result: 

    OK 

    See step  13

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      C55-1 (HA1A) - C77-27 (HA1A) Always Below 1 Ω
      C55-3 (A1A+) - C77-100 (A1A+) Always Below 1 Ω
      C55-4 (A1A-) - C77-132 (A1A-) Always Below 1 Ω
      C55-1 (HA1A) or C77-27 (HA1A) - Body ground and other terminals Always 10 kΩ or higher
      C55-3 (A1A+) or C77-100 (A1A+) - Body ground and other terminals Always 10 kΩ or higher
      C55-4 (A1A-) or C77-132 (A1A-) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    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 [01/2019 - 11/2022]

      HINT: 

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor.

      Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  15

  15. CLEAR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear the DTCs.

      Powertrain > Engine and ECT > Clear DTCs 

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  16

  16. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) 
    1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
    2. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    3. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      Result

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

    Result: 

    A 

    END 

    Result: 

    B 

    See step  17

  17. READ VALUE USING TECHSTREAM (MAF) 
    1. Connect the Techstream to the DLC3.
    2. Start the engine.
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF, Coolant Temp and Engine Speed.

      Powertrain > Engine and ECT > Data List 

      Tester Display
      Engine Speed
      MAF
      Coolant Temp
    5. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
    6. Read MAF with the engine speed at 3000 rpm.

      Standard

      Techstream Display Condition Specified Condition
      MAF
      • Engine warmed up
      • Shift lever position: N (neutral)
      • A/C: Off
      • Engine Speed: 3000 rpm
      		 Between 5.0 and 10.0 gm/sec

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  18

  18. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY CONNECTOR CONNECTION) 
    1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM.

      Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [06/2018 - ]

      HINT: 

      Repair any problems.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  19

  19. CLEAR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear the DTCs.

      Powertrain > Engine and ECT > Clear DTCs 

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  20

  20. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) 
    1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
    2. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    3. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      Result

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

    Result: 

    A 

    END 

    Result: 

    B 

    See step  21

  21. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM) 
    1. Disconnect the mass air flow meter sub-assembly connector.
    2. Disconnect the ECM connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      C26-1 (FG) - C77-137 (VG) Always Below 1 Ω
      C26-2 (E2G) - C77-104 (E2G) Always Below 1 Ω
      C26-3 (VCC) - C77-103 (VCVG) Always Below 1 Ω
      C26-1 (FG) or C77-137 (VG) - Body ground and other terminals Always 10 kΩ or higher
      C26-3 (VCC) or C77-103 (VCVG) - Body ground and other terminals Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  22

  22. REPLACE MASS AIR FLOW METER SUB-ASSEMBLY 
    1. Replace the mass air flow meter sub-assembly.

      Refer to REMOVAL [01/2019 - 11/2022]

      HINT: 

      • If the result of the inspection performed in step 6 and 17 (READ VALUE USING TECHSTREAM (MAF)) indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
      • Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly.

        Refer to INITIALIZATION [01/2019 - 11/2022]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  23

  23. CLEAR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Turn the Techstream on.
    4. Clear the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

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

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  24

  24. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) 
    1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
    2. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    3. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes 

      Result

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

    Result: 

    A 

    END 

    Result: 

    B 

    REPLACE ECM. Refer to  REMOVAL [01/2019 - 03/2019] 

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