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HOMESERVICE MANUALSSUBARU2016LEGACY 2.5IREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS (H4DO) (DIAGNOSTICS) (4 OF 4)DTC P2270 O2 SENSOR SIGNAL BIASED/STUCK LEAN BANK 1 SENSOR 2WIRING DIAGRAM
2016 Subaru Legacy 2.5i

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

2016 Subaru Legacy 2.5iSECTION Wiring Diagram
  • Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
  • Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
    Fig 1: O2 Sensor Signal Biased/Stuck - Wiring Diagram (Lean Bank 1 Sensor 2)
    G10263268Courtesy of SUBARU OF AMERICA, INC.
DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK REAR OXYGEN SENSOR CONNECTOR.  Has water entered the connector? Completely remove any water inside. Go to step 2  .
2 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from ECM and rear oxygen sensor.
  3. Measure the resistance of harness between ECM connector and rear oxygen sensor connector.

    Connector & terminal 

    (E158) No. 56 - (E25) No. 4: 

    (E158) No. 57 - (E25) No. 3: 

 Is the resistance less than 1 Ω? Go to step 3  . Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
3 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 engine ground.

    Connector & terminal 

    (E25) No. 3 (+) - Engine ground (-): 

 Is the voltage 0.15 V or more? Repair the short circuit to power in the harness between ECM connector and rear oxygen sensor connector. Go to step 4  .
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? Repair or replace faulty parts. Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.