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Home >> Subaru >> 2017 >> Legacy 3.6R Limited >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 16 (Engine Control System (Diagnostics) (P0700 To P2097) (H4DO)) >> 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

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

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: Front Oxygen Sensor Wiring Diagram
G11583295Courtesy of SUBARU OF AMERICA, INC.
Fig 2: Rear Oxygen Sensor Wiring Diagram
G11583301Courtesy 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. 46 - (E24) No. 3: 
(E158) No. 33 - (E24) 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 
(E158) No. 46 - Chassis ground: 
(E158) No. 33 - 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. 
  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. 3 (+) - 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 
(E24) No. 4 (+) - 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 
(E24) No. 3 (+) - Chassis ground (-): 
(E24) 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.
  1. Connect the front oxygen (A/F) sensor connector.
  2. Measure the fuel pressure. Ref. to INSPECTION , Fuel Pressure.
CAUTION: Before attaching/detaching a fuel pressure gauge, release the fuel pressure.
 Is the measured value 340 - 400 kPa (3.5 - 4.1 kg/cm2 , 49 - 58 psi)? Go to step 11  Check the fuel pump and fuel delivery line. Ref. to INSPECTION , Fuel Pump. Ref. to INSPECTION , Fuel Delivery and Evaporation Lines.
11 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 "Current Data Display 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 12  Replace the engine coolant temperature sensor. Ref. to ENGINE COOLANT TEMPERATURE SENSOR
12 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 "Current Data Display 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 13  Replace the mass air flow and intake air temperature sensor. Ref. to 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 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 «Intake Air Temp.» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display 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 14  Check the mass air flow and intake air temperature sensor. Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR
14 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 «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Depress the clutch pedal. (MT model)
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display 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 15  Go to step 16 
15 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 «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Depress the clutch pedal. (MT model)
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display 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 17  Go to step 16 
16 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 18 
17 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 «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedures, refer to "Current Data Display 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 for 5 minutes or more? Replace the front oxygen (A/F) sensor. Ref. to FRONT OXYGEN (A/F) SENSOR Go to step 18 
18 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. 57 - (E25) No. 3: 
(E158) No. 56 - (E25) No. 4: 		 Is the resistance less than 1 Ω? Go to step 19  Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
19 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. 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
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