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Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Control System (Diagnostics) (P2101 To U171F) (H4DO)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P219C Cylinder 1 Air-Fuel Ratio Imbalance >> Notes

DTC P219C Cylinder 1 Air-Fuel Ratio Imbalance: Notes

WARNING: This page is about a different variant/trim than selected.

DTC detecting condition: 

Trouble symptom: 

CAUTION:

Wiring diagram: 

Fig 1: Air-Fuel Ratio Imbalance Engine Electrical System Wiring Diagram (1 Of 3)
G11272679Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Air-Fuel Ratio Imbalance Engine Electrical System Wiring Diagram (2 Of 3)
G11272684Courtesy of SUBARU OF AMERICA, INC.
Fig 3: Air-Fuel Ratio Imbalance Engine Electrical System Wiring Diagram (3 Of 3)
G11272676Courtesy 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 connector and front oxygen (A/F) sensor connector.

      Connector & terminal 

      (E158) No. 46 - (E24) No. 3:

      (E158) No. 33 - (E24) No. 4:

    Is the resistance less than 1 Ω?

    • Yes: Go to  3.
    • No: Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
  3. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 

    Measure the resistance between ECM connector and chassis ground.

    Connector & terminal 

    (E158) No. 46 - Chassis ground:

    (E158) No. 33 - Chassis ground:

    Is the resistance 1 MΩ or more? 

    • Yes: Go to  4.
    • No: Repair the short circuit to ground in harness between ECM connector and front oxygen (A/F) sensor connector.
  4. CHECK OUTPUT SIGNAL FOR ECM. 
    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. 3 (+) - Chassis ground (-):

    Is the voltage 4.5 V or more?

    • Yes: Go to  6.
    • No: Go to  5.
  5. CHECK OUTPUT SIGNAL FOR ECM. 

    Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.

    Connector & terminal 

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

    Is the voltage 4.95 V or more? 

    • Yes: Go to  6.
    • No: Go to  7.
  6. CHECK OUTPUT SIGNAL FOR ECM. 

    Measure the voltage between front oxygen (A/F) sensor connector and chassis ground.

    Connector & terminal 

    (E24) No. 3 (+) - Chassis ground (-):

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

    Is the voltage 8 V or more? 

  7. CHECK EXHAUST SYSTEM. 

    Are there holes or loose bolts on exhaust system?

    • Yes: Repair the exhaust system.
    • No: Go to  8.
  8. 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  9.
  9. 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(H4DO)>Fuel Pressure>INSPECTION .
    CAUTION: Before attaching/detaching a fuel pressure gauge, release the fuel pressure.

    Is the measured value 340 - 400 kPa (3.5 - 4.1 kg/cm2, 49 - 58 psi)?

  10. 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?

  11. 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. For CVT models, set the select lever to "P" range or "N" range, and for MT models, place the shift lever in the neutral position.
    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 [Mass Air Flow].
      NOTE:

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

  12. 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. For CVT models, set the select lever to "P" range or "N" range, and for MT models, place the shift lever in the neutral position.
    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 Temp.].
      NOTE:

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

  13. 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 [Oxygen sensor #12].
      NOTE:
      • Depress the clutch pedal (MT model)
      • Subaru Select Monitor

        For detailed procedures, refer to the Data Monitor. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Subaru Select Monitor .

      • General scan tool

        For detailed operation procedures, refer to the general scan tool operation manual.

    Is the value of [Oxygen sensor #12] 0.490 V or more?

    • Yes: Go to  14.
    • No: Go to  15.
  14. 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 [Oxygen sensor #12].
      NOTE:
      • Depress the clutch pedal (MT model)
      • Subaru Select Monitor

        For detailed procedures, refer to the Data Monitor. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Subaru Select Monitor .

      • General scan tool

        For detailed operation procedures, refer to the general scan tool operation manual.

    Is the value of [Oxygen sensor #12] 0.250 V or less?

    • Yes: Go to  16.
    • No: Go to  15.
  15. CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR. 

    Has water entered the connector?

    • Yes: Completely remove any water inside.
    • No: Go to  17.
  16. 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 [Oxygen sensor #12].
      NOTE:

    Is the value of [Oxygen sensor #12] kept at 0.250 V or less for 5 minutes or more?

  17. 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 connector and rear oxygen sensor connector.

      Connector & terminal 

      (E158) No. 57 - (E25) No. 3:

      (E158) No. 56 - (E25) No. 4:

    Is the resistance less than 1 Ω?

    • Yes: Go to  18.
    • No: Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
  18. 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. 3 (+) - Chassis ground (-):

    Is the voltage 0.2 - 0.5 V?

  19. CHECK OUTPUT SIGNAL OF ECM. 
    1. Turn the ignition switch to ON.
    2. Measure the voltage between ECM and chassis ground on faulty cylinders.

      Connector & terminal 

      DTC P219C; #1 (E158) No. 23 (+) - Chassis ground (-):

      DTC P219D; #2 (E158) No. 8 (+) - Chassis ground (-):

      DTC P219E; #3 (E158) No. 9 (+) - Chassis ground (-):

      DTC P219F; #4 (E158) No. 22 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    • Yes: Go to  24.
    • No: Go to  20.
  20. 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 

      DTC P219C; #1 (E5) No. 1 - Engine ground:

      DTC P219D; #2 (E16) No. 1 - Engine ground:

      DTC P219E; #3 (E6) No. 1 - Engine ground:

      DTC P219F; #4 (E17) No. 1 - Engine ground:

    Is the resistance 1 MΩ or more?

    • Yes: Go to  21.
    • No: Repair the short circuit to ground in harness between ECM connector and fuel injector connector.
  21. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR CONNECTOR. 

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

    Connector & terminal 

    DTC P219C; #1 (E158) No. 23 - (E5) No. 1:

    DTC P219D; #2 (E158) No. 8 - (E16) No. 1:

    DTC P219E; #3 (E158) No. 9 - (E6) No. 1:

    DTC P219F; #4 (E158) No. 22 - (E17) No. 1:

    Is the resistance less than 1 Ω?

    • Yes: Go to  22.
    • No: Open circuit in harness between ECM connector and fuel injector connector
  22. CHECK FUEL INJECTOR. 

    Measure the resistance between fuel injector terminals on faulty cylinder.

    Terminals 

    No. 1 -No. 2:

    Is the resistance 5 - 20 Ω?

  23. CHECK POWER SUPPLY LINE. 
    1. Turn the ignition switch to ON.
    2. Measure the voltage between fuel injector connector of faulty cylinders and engine ground.

      Connector & terminal 

      DTC P219C; #1 (E5) No. 2 (+) - Engine ground (-):

      DTC P219D; #2 (E16) No. 2 (+) - Engine ground (-):

      DTC P219E; #3 (E6) No. 2 (+) - Engine ground (-):

      DTC P219F; #4 (E17) No. 2 (+) - Engine ground (-):

    Is the voltage 10 V or more?

    • Yes: Repair the poor contact of all connectors in fuel injector circuit.
    • No: repair the harness and connector.
      NOTE: In this case, repair the following item:
      • Open circuit in harness between the main relay and fuel injector connector on faulty cylinders
      • Poor contact of coupling connector
      • Poor contact of main relay connector
  24. 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. Turn the ignition switch to ON.
    4. Measure the voltage between ECM and chassis ground on faulty cylinders.

      Connector & terminal 

      DTC P219C; #1 (E158) No. 23 (+) - Chassis ground (-):

      DTC P219D; #2 (E158) No. 8 (+) - Chassis ground (-):

      DTC P219E; #3 (E158) No. 9 (+) - Chassis ground (-):

      DTC P219F; #4 (E158) No. 22 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    • Yes: Repair the short circuit to power in harness between ECM connector and fuel injector connectors.
    • No: Go to  25.
  25. CHECK FUEL INJECTOR. 
    1. Turn the ignition switch to OFF.
    2. Measure the resistance between fuel injector terminals on faulty cylinder.

      Terminals 

      No. 1 -No. 2:

    Is the resistance 5 - 20 Ω?

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

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

  27. CHECK CRANKSHAFT POSITION SENSOR PLATE. 

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

  28. 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?

  29. CHECK FUEL LEVEL. 

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

    • Yes: Go to  30.
    • No: Refill the fuel so that the fuel meter indication is higher than the "Lower" level, and proceed to the next step. Go to  30.
  30. CHECK STATUS OF MALFUNCTION INDICATOR LIGHT. 
    1. Clear the memory using the Subaru Select Monitor or general scan tool. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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  32.
    • No: Go to  31.
  31. 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
  32. 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  33.
  33. CHECK MISFIRE SYMPTOM. 
    1. Turn the ignition switch to ON.
    2. Check for DTC. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Read Diagnostic Trouble Code (DTC) .

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

    • Yes: Go to  36.
    • No: Go to  34.
  34. CHECK DTC. 

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

    • Yes: Go to  37.
    • No: Go to  35.
  35. CHECK DTC. 

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

    • Yes: Go to  38.
    • No: Go to  39.
  36. ONLY ONE CYLINDER. 

    Is there any fault in the cylinder?

  37. GROUP OF #1 AND #3 CYLINDERS. 

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

  38. GROUP OF #2 AND #4 CYLINDERS. 

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

  39. CYLINDER AT RANDOM. 

    Is the engine idle rough?

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