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Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Control System (Diagnostics) (P2101 To U171F) (H4DOTC) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P219A Bank 1 Air-Fuel Ratio Imbalance >> Notes

DTC P219A Bank 1 Air-Fuel Ratio Imbalance: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

CAUTION:

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Fig 1: Bank 1 Air-Fuel Ratio Imbalance - Wiring Diagram (1 Of 3)
G11270520Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Bank 1 Air-Fuel Ratio Imbalance - Wiring Diagram (2 Of 3)
G11270524Courtesy of SUBARU OF AMERICA, INC.
Fig 3: Bank 1 Air-Fuel Ratio Imbalance - Wiring Diagram (3 Of 3)
G11270515Courtesy of SUBARU OF AMERICA, INC.
  1. CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR. 

    Has water entered the connector?

    • Yes  : Completely remove any water inside.
    • No  : Go to 2. 
  2. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
    1. Turn the ignition switch to OFF.
    2. Disconnect the connectors from front oxygen (A/F) sensor.
    3. Disconnect the connector from ECM.
    4. Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.

      Connector & terminal 

      (E158) No. 15 - (E24) No. 1:

      (E158) No. 27 - (E24) No. 4:

      (E158) No. 39 - (E24) No. 5:

      Is the resistance less than 1 Ω?

    • Yes  : Go to 3. 
    • No  : repair the harness and connector.
      NOTE: In this case, repair the following item:
      • Open circuit in harness between ECM and front oxygen (A/F) sensor connector
      • Poor contact of coupling connector
  3. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 

    Measure the resistance between ECM and chassis ground.

    Connector & terminal 

    (E158) No. 15 - Chassis ground:

    (E158) No. 27 - Chassis ground:

    (E158) No. 39 - Chassis ground:

    Is the resistance 1 MΩ or more?

    • Yes  : Go to 4. 
    • No  : Repair the ground short circuit of harness between ECM and front oxygen (A/F) sensor connector.
  4. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
    1. Connect the connector to ECM.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.

      Connector & terminal 

      (E24) No. 1 (+) - Chassis ground (-):

      (E24) No. 4 (+) - Chassis ground (-):

      (E24) No. 5 (+) - Chassis ground (-):

      Is the voltage 8 V or more?

    • Yes  : Repair the short circuit to power in the harness between ECM and front oxygen (A/F) sensor connector.
    • No  : Go to 5. 
  5. CHECK EXHAUST SYSTEM. 

    Are there holes or loose bolts on exhaust system?

    • Yes  : Repair the exhaust system.
    • No  : Go to 6. 
  6. CHECK AIR INTAKE SYSTEM. 

    Are there holes, loose bolts or disconnection of hose on air intake system?

    • Yes  : Repair the air intake system.
    • No  : Go to 7. 
  7. CHECK FUEL PRESSURE. 
    WARNING: Place "NO OPEN FLAMES" signs near the working area.
    CAUTION: Be careful not to spill fuel.
    1. Connect the front oxygen (A/F) sensor connector.
    2. Measure the fuel pressure. Ref. to MECHANICAL(H4DOTC)>Fuel Pressure>INSPECTION .
    CAUTION: Release fuel pressure before removing the fuel pressure gauge.

    Is the measured value 328 - 358 kPa (3.3 - 3.7 kgf/cm2 , 48 - 52 psi)?

  8. CHECK ENGINE COOLANT TEMPERATURE SENSOR. 
    1. Start the engine and warm up completely.
    2. Using the Subaru Select Monitor or a general scan tool, read the value of [Coolant Temp.].
    NOTE:

    Is the value of [Coolant Temp.] 75°C (167°F) or more?

  9. CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
    1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
    2. Place the select lever in "P" range or "N" range.
    3. Turn the A/C switch to OFF.
    4. Turn all the accessory switches to OFF.
    5. Using the Subaru Select Monitor or a general scan tool, read the value of [Air Flow Rate from Mass Air Flow Sensor].
    NOTE:

    Is the value of [Air Flow Rate from Mass Air Flow Sensor] 2.0 - 5.0 g/s (0.26 - 0.66 lb/m)?

  10. CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. 
    1. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F).
    2. Place the select lever in "P" range or "N" range.
    3. Turn the A/C switch to OFF.
    4. Turn all the accessory switches to OFF.
    5. Open the front hood.
    6. Measure the ambient temperature.
    7. Using the Subaru Select Monitor or a general scan tool, read the value of [Intake Air Temperature (B1-S1)].
    NOTE:

    Subtract ambient temperature from [Intake Air Temperature (B1-S1)]. Is the obtained value -10 - 50°C (-18 - 90°F)?

  11. CHECK REAR OXYGEN SENSOR DATA. 
    1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and keep the engine speed at 3, 000 RPM. (2 minutes maximum)
    2. Using the Subaru Select Monitor or a general scan tool, read the value of [Bank 1 - Sensor 2 present at that location].
    NOTE:

    Is the value of [Bank 1 - Sensor 2 present at that location] 0.490 V or more?

    • Yes  : Go to 12. 
    • No  : Go to 13. 
  12. CHECK REAR OXYGEN SENSOR DATA. 
    1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and rapidly reduce the engine speed from 3, 000 RPM.
    2. Using the Subaru Select Monitor or a general scan tool, read the value of [Bank 1 - Sensor 2 present at that location].
    NOTE:

    Is the value of [Bank 1 - Sensor 2 present at that location] 0.250 V or less?

    • Yes  : Go to  14.
    • No  : Go to 13. 
  13. CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR. 

    Has water entered the connector?

    • Yes  : Completely remove any water inside.
    • No  : Go to 15. 
  14. CHECK FRONT OXYGEN (A/F) SENSOR USING REAR OXYGEN SENSOR SIGNAL. 
    1. Warm up the engine until engine coolant temperature is higher than 75°C (167°F), then keep the engine idling for 5 minutes or more.
    2. Using the Subaru Select Monitor or a general scan tool, read the value of [Bank 1 - Sensor 2 present at that location].
    NOTE:

    Is the value of [Bank 1 - Sensor 2 present at that location] kept at 0.250 V or less for 5 minutes or more?

  15. CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from rear oxygen sensor.
    3. Disconnect the connector from ECM.
    4. Measure the resistance of harness between ECM and rear oxygen sensor connector.

      Connector & terminal 

      (E158) No. 42 - (E25) No. 3:

      (E158) No. 16 - (E25) No. 4:

      Is the resistance less than 1 Ω?

    • Yes  : Go to 16. 
    • No  : repair the harness and connector.
      NOTE: In this case, repair the following item:
      • Open circuit in harness between ECM and rear oxygen sensor connector
      • Poor contact of coupling connector
  16. CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
    1. Connect the connector to ECM.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between rear oxygen sensor connector and chassis ground.

      Connector & terminal 

      (E25) No. 4 (+) - Chassis ground (-):

      Is the voltage 0.2 - 0.5 V?

  17. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR. 
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from fuel injector on faulty cylinders.
    3. Measure the resistance between fuel injector connector and engine ground on faulty cylinders.

      Connector & terminal 

      #1 (E5) No. 1 - Engine ground:

      #1 (E5) No. 2 - Engine ground:

      #2 (E16) No. 1 - Engine ground:

      #2 (E16) No. 2 - Engine ground:

      #3 (E6) No. 1 - Engine ground:

      #3 (E6) No. 2 - Engine ground:

      #4 (E17) No. 1 - Engine ground:

      #4 (E17) No. 2 - Engine ground:

      Is the resistance 1 MΩ or more?

    • Yes  : Go to 18. 
    • No  : Repair the short circuit to ground in harness between ECM and fuel injector connector.
  18. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR. 

    Measure the resistance of harness between ECM and fuel injector connector on faulty cylinders.

    Connector & terminal 

    #1 (E158) No. 12 - (E5) No. 1:

    #1 (E158) No. 11 - (E5) No. 2:

    #2 (E158) No. 24 - (E16) No. 1:

    #2 (E158) No. 23 - (E16) No. 2:

    #3 (E158) No. 36 - (E6) No. 1:

    #3 (E158) No. 35 - (E6) No. 2:

    #4 (E158) No. 48 - (E17) No. 1:

    #4 (E158) No. 47 - (E17) No. 2:

    Is the resistance less than 1 Ω?

    • Yes  : Go to 19. 
    • No  : Repair the open circuit in harness between ECM and fuel injector connector.
  19. CHECK FUEL INJECTOR. 

    Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Injector>INSPECTION .

    Are fuel injectors OK?

  20. CHECK INSTALLATION CONDITION OF CAMSHAFT POSITION SENSOR/CRANKSHAFT POSITION SENSOR. 

    Is the camshaft position sensor or crankshaft position sensor loosely installed?

  21. CHECK CRANKSHAFT POSITION SENSOR PLATE. 

    Is the crankshaft position sensor plate rusted or does it have broken teeth?

  22. CHECK INSTALLATION CONDITION OF TIMING CHAIN. 

    Turn the crankshaft using ST, and align the alignment mark on crank sprocket with alignment mark on cylinder block.

    ST 18252AA000 CRANKSHAFT SOCKET 

    Is the timing chain dislocated from its proper position?

  23. CHECK FUEL LEVEL. 

    Is the fuel meter indication higher than the "Lower" level?

    • Yes  : Go to 24. 
    • No  : Refill the fuel so that the fuel meter indication is higher than the "Lower" level, and proceed to the next step. Go to 24. 
  24. CHECK STATUS OF MALFUNCTION INDICATOR LIGHT. 
    1. Clear the memory using the Subaru Select Monitor or general scan tool. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Clear Memory Mode .
    2. Start the engine, and drive the vehicle 10 minutes or more.

      Does the malfunction indicator light illuminate or blink?

    • Yes  : Go to  26.
    • No  : Go to 25. 
  25. CHECK CAUSE OF MISFIRE. 

    Was the cause of misfire identified when the engine is running?

    • Yes  : Finish diagnostics operation, if the engine has no abnormality.
    • No  : Repair the poor contact of connector.
      NOTE: In this case, repair the following item:
      • Poor contact of ignition coil connector
      • Poor contact of fuel injector connector on faulty cylinders
      • Poor contact of ECM connector
      • Poor contact of coupling connector
  26. CHECK AIR INTAKE SYSTEM. 

    Is there any fault in air intake system?

    • Yes  : Repair the air intake system.
      NOTE: Check the following items.
      • Are there air leaks or air suction caused by loose or dislocated nuts and bolts?
      • Are there cracks or any disconnection of hoses?
    • No  : Go to 27. 
  27. CHECK MISFIRE SYMPTOM. 
    1. Turn the ignition switch to ON.
    2. Check for DTC. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Read Diagnostic Trouble Code (DTC) .

      Does the Subaru Select Monitor or general scan tool indicate only one DTC?

    • Yes  : Go to  30.
    • No  : Go to 28. 
  28. CHECK DTC. 

    Is DTC P0301 and P0303 displayed on the Subaru Select Monitor or general scan tool?

    • Yes  : Go to 31. 
    • No  : Go to 29. 
  29. CHECK DTC. 

    Is DTC P0302 and P0304 displayed on the Subaru Select Monitor or general scan tool?

    • Yes  : Go to  32.
    • No  : Go to  33.
  30. ONLY ONE CYLINDER. 

    Is there any fault in the cylinder?

  31. GROUP OF #1 AND #3 CYLINDERS. 

    Are there any faults in #1 and #3 cylinders?

  32. GROUP OF #2 AND #4 CYLINDERS. 

    Are there any faults in #2 and #4 cylinders?

  33. CYLINDER AT RANDOM. 

    Is the engine idle rough?

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