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.>.

WIRING DIAGRAM:

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

Fig 1: Post Catalyst Fuel Trim System Too Rich Bank 1 Wiring Diagram (1 Of 2)

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Post Catalyst Fuel Trim System Too Rich Bank 1 Wiring Diagram (2 Of 2)

Courtesy 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. Turn the ignition switch to OFF. Disconnect the connector from ECM. Disconnect the connectors from front oxygen (A/F) sensor. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector. Connector & terminal (B136) No. 18 - (B379) No. 3: (B136) No. 19 - (B379) No. 4:	Is the resistance less than 1 Ω?	Go to step 4 .	Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
4 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. Measure the resistance between ECM connector and chassis ground. Connector & terminal (B136) No. 18 - Chassis ground: (B136) No. 19 - 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 OUTPUT SIGNAL FOR ECM. Connect the connector to ECM. Turn the ignition switch to ON. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground. Connector & terminal (B379) No. 4 (+) - Chassis ground (-):	Is the voltage 4.5 V or more?	Go to step 7 .	Go to step 6 .
6 CHECK OUTPUT SIGNAL FOR ECM. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground. Connector & terminal (B379) No. 3 (+) - Chassis ground (-):	Is the voltage 4.95 V or more?	Go to step 7 .	Go to step 8 .
7 CHECK OUTPUT SIGNAL FOR ECM. Measure the voltage between front oxygen (A/F) sensor connector and chassis ground. Connector & terminal (B379) No. 3 (+) - Chassis ground (-): (B379) No. 4 (+) - 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. After repair, replace the ECM. <Ref. to Engine Control Module (ECM) .>	Repair the poor contact of ECM connector.
8 CHECK EXHAUST SYSTEM.	Are there holes or loose bolts on exhaust system?	Repair the exhaust system.	Go to step 9 .
9 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 10 .
10 CHECK FUEL PRESSURE. WARNING: Place "NO OPEN FLAMES" signs near the working area. CAUTION: Be careful not to spill fuel. Connect the front oxygen (A/F) sensor connector. Measure the fuel pressure while disconnecting pressure regulator vacuum hose from intake manifold. <Ref. to INSPECTION , Fuel Pressure.> CAUTION: Release fuel pressure before removing the fuel pressure gauge. NOTE: If fuel pressure does not increase, squeeze the fuel return hose 2 to 3 times, then measure fuel pressure again.	Is the measured value 284 - 314 kPa (2.9 - 3.2 kgf/cm² , 41 - 46 psi)?	Go to step 11 .	Check the fuel pump and fuel delivery line. <Ref. to INSPECTION , Fuel Pump.> <Ref. to INSPECTION , Fuel Delivery, Return and Evaporation Lines.>
11 CHECK FUEL PRESSURE. After connecting the pressure regulator vacuum hose, measure fuel pressure. <Ref. to INSPECTION , Fuel Pressure.> CAUTION: Release fuel pressure before removing the fuel pressure gauge. NOTE: If fuel pressure does not increase, squeeze fuel return hose 2 to 3 times, then measure fuel pressure again. If the measured value at this step is out of specification, check or replace pressure regulator and pressure regulator vacuum hose.	Is the measured value 230 - 260 kPa (2.4 - 2.7 kgf/cm² , 33 - 38 psi)?	Go to step 12 .	Check the fuel pump and fuel delivery line. <Ref. to INSPECTION , Fuel Pump.> <Ref. to INSPECTION , Fuel Delivery, Return and Evaporation Lines.>
12 CHECK ENGINE COOLANT TEMPERATURE SENSOR. Start the engine and warm up completely. 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 13 .	Replace the engine coolant temperature sensor. <Ref. to Engine Coolant Temperature Sensor .>
13 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F). Place the shift lever in neutral position. Turn the A/C switch to OFF. Turn all the accessory switches to OFF. 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 of «Mass Air Flow» 2.0 - 5.0 g/s (0.26 - 0.66 lb/m)?	Go to step 14 .	Replace the mass air flow and intake air temperature sensor. <Ref. to Mass Air Flow and Intake Air Temperature Sensor .>
14 CHECK MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR. Start the engine and warm up engine until coolant temperature is higher than 75°C (167°F). Place the shift lever in neutral position. Turn the A/C switch to OFF. Turn all the accessory switches to OFF. Open the front hood. Measure the ambient temperature. Read the value of «Intake Air 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.	Subtract ambient temperature from «Intake Air Temp.». Is the obtained value -10 - 50°C (-18 - 90°F)?	Go to step 15 .	Check the mass air flow and intake air temperature sensor. <Ref. to Mass Air Flow and Intake Air Temperature Sensor .>
15 CHECK REAR OXYGEN SENSOR DATA. 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) Read the value of «Rear O2 Sensor Voltage» using the Subaru Select Monitor or a general scan tool. NOTE: Depress the clutch pedal. 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 «Rear O2 Sensor Voltage» 0.490 V or more?	Go to step 16 .	Go to step 17 .
16 CHECK REAR OXYGEN SENSOR DATA. 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. Read the value of «Rear O2 Sensor Voltage» using the Subaru Select Monitor or a general scan tool. NOTE: Depress the clutch pedal. 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 «Rear O2 Sensor Voltage» 0.250 V or less?	Go to step 18 .	Go to step 17 .
17 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.	Has water entered the connector?	Completely remove any water inside.	Go to step 19 .
18 CHECK FRONT OXYGEN (A/F) SENSOR USING REAR OXYGEN SENSOR SIGNAL. 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. Read the value of «Rear O2 Sensor Voltage» 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 «Rear O2 Sensor Voltage» 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 19 .
19 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Disconnect the connector from rear oxygen sensor. Measure the resistance of harness between ECM connector and rear oxygen sensor connector. Connector & terminal (B136) No. 20 - (T6) No. 3: (B135) No. 30 - (T6) No. 4:	Is the resistance less than 1 Ω?	Go to step 20 .	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
20 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. Connect the connector to ECM. Turn the ignition switch to ON. Measure the voltage between rear oxygen sensor connector and chassis ground. Connector & terminal (T6) No. 3 (+) - 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