Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSUBARU2005OUTBACK I, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - ENGINE (DIAGNOSTICS) (H4SO)DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)DTC P0139 O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2)
2005 Subaru Outback i, Standard
DTC P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
2005 Subaru Outback i, StandardSECTION DTC P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
DTC DETECTING CONDITION:
- Two consecutive driving cycles with fault
- GENERAL DESCRIPTION < Ref. to DTC P0139 02 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2) , Diagnostic Trouble Code (DTC) Detecting Criteria. >
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode < Ref. to
, OPERATION , Clear Memory Mode.> and Inspection Mode < Ref. to
, PROCEDURE , Inspection Mode.>.
WIRING DIAGRAM:
DTC P0139 O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2) DIAGNOSIS
| 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) . >
NOTE:
In this case, it is not necessary to inspect DTC P0139.
|
Go to step 2. |
2. CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
|
Is the resistance less than 1 Ω? | Go to step 3. | Repair open circuit in harness between ECM and rear oxygen sensor connector. |
| 3. CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR. Measure the resistance between rear oxygen sensor harness connector and chassis ground. Connector & terminal (B19) No. 3 - Chassis ground: |
Is the resistance more than 1 MΩ? | Go to step 4. | Repair short circuit to ground in harness. |
| 4. CHECK REAR OXYGEN SENSOR DATA. Measure the resistance between connector terminals of rear oxygen sensor. Terminals No. 3 - No. 4: |
Is the resistance less than 1 Ω? | Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . > | A temporary poor compact occurs. Check poor contact in connector. |
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.