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DTC P2097: Post Catalyst Fuel Trim System Too Rich Bank 1: 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.

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM (IMPREZA MODEL)>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

G13608025Courtesy of SUBARU OF AMERICA, INC.
G13608037Courtesy of SUBARU OF AMERICA, INC.
G13941289Courtesy of SUBARU OF AMERICA, INC.
G13608038Courtesy 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 DTC  .

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

    Is DTC other than P2097 displayed? (Current malfunction)

    Yes:  Check the appropriate DTC using the "Diagnostic Trouble Code (DTC)". Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC TROUBLE CODE (DTC) .

    No:  Go to  2.

  2. 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  3.

  3. 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  4.

    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
  4. 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  5.

    No:  Repair the short circuit to ground in harness between ECM connector and front oxygen (A/F) sensor connector.

  5. 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  7.

    No:  Go to  6.

  6. 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  7.

    No:  Go to  8.

  7. 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.

  8. CHECK EXHAUST SYSTEM  .

    Check exhaust system parts.

    Are there holes or loose bolts on exhaust system?

    Yes:  Repair the exhaust system.

    No:  Go to  9.

  9. 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  10.

  10. 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>INSPECTION .

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

    Yes:  Go to  11.

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

  11. 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  12.

    No:  Replace the engine coolant temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>ENGINE COOLANT 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. 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  13.

    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 .

  13. 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  14.

    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 .

  14. 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  15.

    No:  Go to  16.

  15. 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  17.

    No:  Go to  16.

  16. 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  18.

  17. 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 voltage of [Oxygen sensor #12] kept at 0.8 V or more 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  18.

  18. 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  19.

    No:  Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.

  19. 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:  Repair the harness and connector.

    NOTE: In this case, repair the following item:
    • Open circuit in harness between ECM connector and rear oxygen sensor connector
    • Poor contact of ECM connector
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