LEMON Manuals: Even more car manuals for everyone
Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Control System (Diagnostics) (P0700 To P2097) (H4DOTC) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P2096 Post Catalyst Fuel Trim System Too Lean Bank 1 >> Notes

DTC P2096 Post Catalyst Fuel Trim System Too Lean Bank 1: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

CAUTION:

Wiring diagram: 

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

Fig 1: Post Catalyst Fuel Trim System Too Lean Bank 1 - Wiring Diagram (1 Of 2)
G11270520Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Post Catalyst Fuel Trim System Too Lean Bank 1 - Wiring Diagram (2 Of 2)
G11270524Courtesy of SUBARU OF AMERICA, INC.
  1. CHECK FOR ANY OTHER DTC ON DISPLAY. 

    Is any other DTC displayed?

  2. CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR. 

    Has water entered the connector?

    • Yes  : Completely remove any water inside.
    • No  : Go to 3. 
  3. 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 4. 
      • 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
  4. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 

    Measure the resistance between ECM and chassis ground.

    Connector & terminal 

    (B158) No. 15 - Chassis ground:

    (B158) No. 27 - Chassis ground:

    (B158) No. 39 - Chassis ground:

    Is the resistance 1 MΩ or more?

    • Yes  : Go to 5. 
    • No  : Repair the ground short circuit of harness between ECM and front oxygen (A/F) sensor connector.
  5. 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 6. 
  6. CHECK EXHAUST SYSTEM. 

    Are there holes or loose bolts on exhaust system?

    • Yes  : Repair the exhaust system.
    • No  : Go to 7. 
  7. 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 8. 
  8. 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)?

  9. 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:
      • Subaru Select Monitor

        For detailed procedures, refer to "Data Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Subaru Select Monitor .

      • General scan tool

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

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

  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. 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/s)?

  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. 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)?

  12. 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 13. 
    • No  : Go to  14.
  13. 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 more?

    • Yes  : Go to  15.
    • No  : Go to 14. 
  14. CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR. 

    Has water entered the connector?

    • Yes  : Completely remove any water inside.
    • No  : Go to  16.
  15. 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?

  16. 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 17. 
    • 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
  17. 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?

    • Yes  : Replace the rear oxygen sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Rear Oxygen Sensor .
    • 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 ECM connector
      • Poor contact of coupling connector
scientia non olet · About LEMON Manuals