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Home >> Subaru >> 2017 >> WRX Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System (Diagnostics) (P0700 To P2097) (2.0L) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P2097 Post Catalyst Fuel Trim System Too Rich Bank 1 >> Notes

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

DTC DETECTING CONDITION: 

Detected when two consecutive driving cycles with fault occur.

CAUTION:
  • After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to OPERATION , Clear Memory Mode.>, and Inspection Mode <Ref. to PROCEDURE , Inspection Mode.>.
  • Use the check board when measuring the ECM terminal voltage and resistance.

WIRING DIAGRAM: 

Engine Electrical System <Ref. to WIRING DIAGRAM , Engine Electrical System.>

Fig 1: Engine Stall History - Wiring Diagram (2 Of 7)
G11577046Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Post Catalyst Fuel Trim System Too Lean Bank 1 - Wiring Diagram (2 Of 2)
G11577050Courtesy of SUBARU OF AMERICA, INC.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY.  Is any other DTC displayed? Check DTC using "List of Diagnostic Trouble Code (DTC)". <Ref. to List of Diagnostic Trouble Code (DTC) .> Go to step 2  .
2 CHECK FRONT OXYGEN (A/F) SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 3  .
3 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM.
  3. Disconnect the connectors from front oxygen (A/F) sensor.
  4. Measure the resistance of harness between ECM connector 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? Go to step 4  . 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 CONNECTOR. 
Measure the resistance between ECM connector 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? Go to step 5  . Repair the short circuit to ground in harness between ECM connector 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? Repair the short circuit to power in the harness between ECM connector and front oxygen (A/F) sensor connector. Go to step 6  .
6 CHECK EXHAUST SYSTEM.  Are there holes or loose bolts on exhaust system? Repair the exhaust system. Go to step 7  .
7 CHECK AIR INTAKE SYSTEM.  Are there holes, loose bolts or disconnection of hose on air intake system? Repair the air intake system. Go to step 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 INSPECTION , Fuel Pressure.>
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)? Go to step 9  . Check the fuel pump and fuel delivery line. <Ref. to INSPECTION , Fuel Pump.> <Ref. to INSPECTION , Fuel Delivery and Evaporation Lines.>
9 CHECK ENGINE COOLANT TEMPERATURE SENSOR. 
  1. Start the engine and warm up completely.
  2. Read the value of «Coolant Temp.» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to 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? Go to step 10  . Replace the engine coolant temperature sensor. <Ref. to Engine Coolant Temperature Sensor .>
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. 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. Read the value of «Mass Air Flow» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to Subaru Select Monitor .>

  • General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.
 Is the value in «Mass Air Flow» 2.0 - 5.0 g/s (0.26 - 0.66 lb/s)? Go to step 11  . Replace the mass air flow and intake air temperature sensor. <Ref. to Mass Air Flow and Intake Air Temperature Sensor .>
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. Open the front hood.
  6. Measure the ambient temperature.
  7. Read the value of «IAT Sensor #11» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to Subaru Select Monitor .>

  • General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.
 Subtract ambient temperature value from the value of «IAT Sensor #11». Is the obtained value -10 - 50°C (-18 - 90°F)? Go to step 12  . Check the mass air flow and intake air temperature sensor. <Ref. to Mass Air Flow and Intake Air Temperature Sensor .>
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. Read the value of «O2 Sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to 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? Go to step 13  . Go to step 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. Read the value of «O2 Sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to 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? Go to step 15  . Go to step 14  .
14 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 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. Read the value of «O2 Sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Read Current Data For Engine". <Ref. to 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» kept at 0.8 V or more for 5 minutes or more? Replace the front oxygen (A/F) sensor. <Ref. to Front Oxygen (A/F) Sensor .> Go to step 16  .
16 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM.
  3. Disconnect the connector from rear oxygen sensor.
  4. Measure the resistance of harness between ECM connector 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? Go to step 17  . 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 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? Replace the rear oxygen sensor. <Ref. to Rear Oxygen Sensor .> 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
  • Poor contact of coupling connector
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