DTC P2270: O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 2: Notes

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DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Wiring diagram:

Engine Electrical system. Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Refer to ENGINE (DIAGNOSTICS) (H4DO)>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. Refer to ENGINE (DIAGNOSTICS) (H4DO)>Basic Diagnostic Procedure>PROCEDURE .

CHECK REAR OXYGEN SENSOR CONNECTOR .
1. Turn the ignition switch to OFF.
2. Check the rear oxygen sensor connector.
  Has water entered the connector?
  
  Yes : Completely remove any water inside.
  
  No : Go to 2.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR (OPEN) .
1. Disconnect the connector from ECM.
2. Disconnect the connector from the rear oxygen sensor.
3. Measure the resistance of harness between ECM connector and rear oxygen sensor connector.
  Connector & terminal
  
  (B62) No. 33 - (B95) No. 3:
  
  (B62) No. 44 - (B95) No. 4:
  
  Is the resistance less than 1 Ω?
  
  Yes : Go to 3.
  
  No : Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR (SHORT TO POWER SUPPLY) .
1. Connect the connector to ECM.
2. Turn the ignition switch to ON.
3. Measure the voltage between rear oxygen sensor connector and engine ground.
  Connector & terminal
  
  (B95) No. 3 (+) - Engine ground (-):
  
  Is the voltage 0.15 V or more?
  
  Yes : Repair the short circuit to power supply in harness between ECM connector and rear oxygen sensor connector.
  
  No : Go to 4.
CHECK EXHAUST SYSTEM .
Check exhaust system parts.
NOTE:
Check the following items.
- Looseness and improper fitting of exhaust system parts
- Damage (crack, hole etc.) of parts
- Damage (crack, hole etc.) between front oxygen (A/F) sensor and rear oxygen sensor
Is there any fault in exhaust system?

Yes : Repair or replace faulty parts.

No : Replace the rear oxygen sensor. Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>REAR OXYGEN SENSOR .