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DTC P219C: Cylinder 1 Air-Fuel Ratio Imbalance: Notes

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

1. - 

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

G13608026Courtesy of SUBARU OF AMERICA, INC.
G13608038Courtesy of SUBARU OF AMERICA, INC.
G13614578Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
  1. CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR  .

    Check the 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 (OPEN)  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Disconnect the connector from the front oxygen (A/F) sensor.
    4. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector.

      Connector and terminal 

      (E158) No. 3 - (B379) No. 3:

      (E158) No. 4 - (B379) No. 4:

      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 connector and front oxygen (A/F) sensor connector
      • Poor contact of coupling connector
  3. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR (SHORT TO GROUND)  .

    Measure the resistance between ECM connector and chassis ground.

    Connector and terminal 

    (E158) No. 3 - Chassis ground:

    (E158) No. 4 - 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 and terminal 

      (B379) 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 and terminal 

    (B379) 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 and terminal 

    (B379) No. 3 (+) - Chassis ground (-):

    (B379) No. 4 (+) - Chassis ground (-):

    Is the voltage 8 V or more?

    Yes:  Repair the short circuit to power in the harness between ECM connector and front oxygen (A/F) sensor connector. After repair, replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>ENGINE CONTROL MODULE (ECM) .

    No:  Repair the poor contact of ECM connector.

  7. CHECK EXHAUST SYSTEM  .

    Check exhaust system parts.

    Are there holes or loose bolts on exhaust system?

    Yes:  Repair the exhaust system.

    No:  Go to  8.

  8. CHECK AIR INTAKE SYSTEM  .

    Check the installing condition of the 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.
    • Before attaching/detaching a fuel pressure gauge, release the fuel pressure.
    1. Connect the front oxygen (A/F) sensor connector.
    2. Measure the fuel pressure. Ref. to MECHANICAL (H4DO (EXCEPT FOR HEV))>FUEL PRESSURE .

      Is the measured value 350 - 450 kPa (3.5 - 4.6 kg/cm2, 50 - 66 psi)?

      Yes:  Go to  10.

      No:  Check the fuel pump and fuel delivery line. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FUEL PUMP . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FUEL DELIVERY AND EVAPORATION LINES .

  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 [Engine Coolant Temperature].
      NOTE:
      • Subaru Select Monitor

        For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

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

      Yes:  Go to  11.

      No:  Replace the engine coolant temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>ENGINE COOLANT TEMPERATURE SENSOR .

  11. CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR  .
    1. Start the engine and warm up until the engine coolant temperature exceeds 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:
      • Subaru Select Monitor

        For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

      Is the value of [Mass Air Flow] 2 - 5 g/s (0.26 - 0.66 lb/min)?

      Yes:  Go to  12.

      No:  Replace the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .

  12. CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR  .
    1. Start the engine and warm up until the engine coolant temperature exceeds 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:
      • Subaru Select Monitor

        For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

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

      Yes:  Go to  13.

      No:  Check the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR .

  13. CHECK REAR OXYGEN SENSOR DATA  .
    1. Warm up the engine until the engine coolant temperature exceeds 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 operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

      Is the value of [Oxygen sensor #12] 0.49 V or more?

      Yes:  Go to  14.

      No:  Go to  15.

  14. CHECK REAR OXYGEN SENSOR DATA  .
    1. Warm up the engine until the engine coolant temperature exceeds 75°C (167°F), and decrease the engine speed rapidly 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 operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

      Is the value of [Oxygen sensor #12] 0.25 V or less?

      Yes:  Go to  16.

      No:  Go to  15.

  15. CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR  .

    Check the 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 the engine coolant temperature exceeds 75°C (167°F) and leave it at 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:
      • Subaru Select Monitor

        For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON (DIAG)>DATA MONITOR .

      • General scan tool

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

      Is the value of [Oxygen sensor #12] kept at 0.25 V or less for 5 minutes or more?

      Yes:  Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FRONT OXYGEN (A/F) SENSOR .

      No:  Go to  17.

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

      Connector and terminal 

      (B134) No. 33 - (B19) No. 3:

      (B134) No. 44 - (B19) 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  .
    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 and terminal 

      (B19) No. 3 (+) - Chassis ground (-):

      Is the voltage 0.2 - 0.5 V?

      Yes:  Replace the rear oxygen sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>REAR OXYGEN SENSOR .

      No:  Go to  19.

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

      Connector and 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  20.

      No:  Repair the short circuit to ground in harness between ECM and fuel injector connector.

  20. CHECK HARNESS BETWEEN ECM AND FUEL INJECTOR  .

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

    Connector and terminal 

    #1 (E158) No. 96 - (E5) No. 1:

    #1 (E158) No. 87 - (E5) No. 2:

    #2 (E158) No. 95 - (E16) No. 1:

    #2 (E158) No. 86 - (E16) No. 2:

    #3 (E158) No. 93 - (E6) No. 1:

    #3 (E158) No. 84 - (E6) No. 2:

    #4 (E158) No. 94 - (E17) No. 1:

    #4 (E158) No. 85 - (E17) No. 2:

    Is the resistance less than 1 Ω?

    Yes:  Go to  21.

    No:  Repair the harness and connector.

    NOTE: In this case, repair the following item:
    • Open circuit in harness between ECM and fuel injector connector
    • Poor contact of coupling connector
  21. CHECK FUEL INJECTOR  .

    Check the fuel injector on faulty cylinder. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FUEL INJECTOR .

    Is the check result OK?

    Yes:  Go to  22.

    No:  Replace the faulty fuel injector. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FUEL INJECTOR .

  22. CHECK INSTALLATION CONDITION OF CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR  .

    Check the installation condition of the camshaft position sensor and crankshaft position sensor.

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

    Yes:  Tighten the camshaft position sensor or crankshaft position sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>CAMSHAFT POSITION SENSOR . Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>CRANKSHAFT POSITION SENSOR .

    No:  Go to  23.

  23. CHECK CRANKSHAFT POSITION SENSOR PLATE  .

    Check the crankshaft position sensor plate.

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

    Yes:  Replace the crankshaft position sensor plate. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>CRANKSHAFT POSITION SENSOR PLATE .

    No:  Go to  24.

  24. 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?

    Yes:  Correct the installation condition of timing chain. Ref. to MECHANICAL (H4DO (EXCEPT FOR HEV))>TIMING CHAIN ASSEMBLY .

    No:  Go to  25.

  25. CHECK FUEL LEVEL  .

    Check the fuel gauge display.

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

    Yes:  Go to  26.

    No:  Refill the fuel so that the fuel meter indication is higher than the "Lower" level, and proceed to the next step. Go to  26.

  26. CHECK STATUS OF MALFUNCTION INDICATOR LIGHT  .
    1. Using the Subaru Select Monitor or a general scan tool, perform the clear memory of [Engine]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
    2. Start the engine, and drive the vehicle at 60 km/h (37.3 MPH) or more for 10 minutes or more.

      Does the malfunction indicator light illuminate or blink?

      Yes:  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

      No:  Go to  27.

  27. CHECK AIR INTAKE SYSTEM  .

    Check the installing condition of the 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  28.

  28. CHECK MISFIRE SYMPTOM  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is there only one DTC displayed? (Current malfunction)

      Yes:  Go to  31.

      No:  Go to  29.

  29. CHECK DTC  .

    Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Are DTC P0301 and P0303 displayed? (Current malfunction)

    Yes:  Go to  32.

    No:  Go to  30.

  30. CHECK DTC  .

    Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

    Are DTC P0302 and P0304 displayed? (Current malfunction)

    Yes:  Go to  33.

    No:  Go to  34.

  31. ONLY ONE CYLINDER  .

    Check the following items for only one cylinder.

    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure

    Is there any fault in the cylinder?

    Yes:  Repair or replace faulty parts.

    NOTE: Check the following items.
    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure

    No:  Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171: SYSTEM TOO LEAN BANK 1 .

  32. GROUP OF #1 AND #3 CYLINDERS  .

    Check the following items for the bank RH (cylinder #1, #3).

    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure
    • Skipping timing chain teeth

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

    Yes:  Repair or replace faulty parts.

    NOTE: Check the following items.
    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure
    • Skipping timing chain teeth

    No:  Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171: SYSTEM TOO LEAN BANK 1 .

  33. GROUP OF #2 AND #4 CYLINDERS  .

    Check the following items for the bank LH (cylinder #2, #4).

    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure
    • Skipping timing chain teeth

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

    Yes:  Repair or replace faulty parts.

    NOTE: Check the following items.
    • Spark plug
    • Ignition coil
    • Fuel injector
    • Compression pressure
    • Skipping timing chain teeth

    No:  Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171: SYSTEM TOO LEAN BANK 1 .

  34. CYLINDER AT RANDOM  .
    1. Start the engine.
    2. Check the idling condition.

      Is the engine idle rough?

      Yes:  Go to DTC P0171. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)>DTC P0171: SYSTEM TOO LEAN BANK 1 .

      No:  Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

      NOTE: In this case, temporary open or short circuit of harness or temporary poor contact of connector may be the cause.
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