DTC P2271: O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Failure detection pattern: 

• "Primary" (high-priority diagnosis)

Warning light/indicator light: 

• Malfunction indicator light

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM>2.0 L MODEL .

Courtesy of SUBARU OF AMERICA, INC.

1. BASIC INSPECTION  .

   Before performing the diagnosis, perform basic inspection. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>GENERAL DESCRIPTION>INSPECTION .

   NOTE:

   • Check the battery and its installation condition.
   • Check the related fuse.
   • Visually check that the related connectors are properly connected.

     Also, check the related ground terminal for looseness and corrosion.

   Is the check result OK?

   Yes  : GO TO  2.

   No  : Repair the defective part.

   After the repair, GO TO  6.

2. CHECK REAR OXYGEN SENSOR CONNECTOR  .

   Check the rear oxygen sensor connector.

   Has water entered the connector?

   Yes  : Completely remove any water inside.

   After operation, GO TO  6.

   No  : GO TO  3.

3. CHECK HARNESS (OPEN CIRCUIT IN REAR OXYGEN SENSOR SIGNAL LINE)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
      CAUTION: When disconnecting the connector, check for poor contact due to damage, looseness, adherence of foreign matter on the connector and terminal.
   3. Disconnect the connector from the rear oxygen sensor.
      CAUTION: When disconnecting the connector, check for poor contact due to damage, looseness, adherence of foreign matter on the connector and terminal.
   4. Measure the resistance between the following terminals.

      Connector & terminal: Standard 

      (B62) No. 44 - (B95) No. 4: Less than 1 Ω

      (B62) No. 33 - (B95) No. 3: Less than 1 Ω

   Is the check result OK?

   Yes  : GO TO  4.

   No  : Repair the defective part.

   After the repair, GO TO  6.

4. CHECK HARNESS (SHORT TO GROUND IN REAR OXYGEN SENSOR SIGNAL LINE)  .

   Measure the resistance between the following terminals.

   Connector & terminal: Standard 

   (B62) No. 33 - Chassis ground: 10 KΩ or more

   Is the check result OK?

   Yes  : GO TO  5.

   No  : Repair the defective part.

   After the repair, GO TO  6.

5. 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.) of front oxygen (A/F) sensor and rear oxygen sensor

   Is there any fault in exhaust system?

   Yes  : Repair or replace faulty parts.

   After operation, GO TO  6.

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

   After replacement, GO TO  6.

6. CHECK REPAIR  .
   1. Perform the inspection mode corresponding to DTC. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>INSPECTION MODE>PROCEDURE .
   2. Confirm that DTC or cancel code is not stored and the malfunction is eliminated.

   Is the check result OK?

   Yes  : Finish the diagnosis.

   No  : Perform the diagnosis according to the basic diagnostic procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .