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HOMESERVICE MANUALSSUBARU2005OUTBACK I, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - ENGINE (DIAGNOSTICS) (H4SO)DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1)
2005 Subaru Outback i, Standard

DTC P0030 Ho2S Heater Control Circuit (Bank 1 Sensor 1)

2005 Subaru Outback i, StandardSECTION DTC P0030 Ho2S Heater Control Circuit (Bank 1 Sensor 1)

DTC DETECTING CONDITION: 

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: 

Fig 1: DTC P0030 HO2S Heater Control Circuit (Bank 1 Sensor 1)
G03828442Courtesy of SUBARU OF AMERICA, INC.
DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1) DIAGNOSIS

Step Check Yes No
1. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
  1. Start the engine and warm-up engine.
  2. Turn the ignition switch to OFF.
  3. Disconnect the connectors from ECM and front oxygen (A/F) sensor.
  4. Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.

    Connector & terminal 

    (B134) No. 2 - (B395) No. 4: 

    (B134) No. 3 - (B395) No. 4: 

 Is the resistance less than 1 Ω? Go to step 2.  Repair the open circuit in harness between ECM and front oxygen (A/F) sensor connector.
2. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.
Connector & terminal 
(B134) No. 33 - (B395) No. 1: 
(B134) No. 26 - (B395) No. 3: 		 Is the resistance less than 1 Ω? Go to step 3.  Repair the open circuit in harness between main relay and front oxygen (A/F) sensor connector.
3. CHECK HARNESS BETWEEN A/F AND OXYGEN SENSOR RELAY AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 
Measure the resistance of harness between oxygen sensor relay and front oxygen (A/F) sensor connector.
Connector & terminal 
(B327) No. 4 - (B395) No. 6: 		 Is the resistance less than 1 Ω? Go to step 4.  Repair the open circuit in harness between oxygen sensor relay and front oxygen (A/F) sensor connector.
4. CHECK FRONT OXYGEN (A/F) SENSOR. 
Measure the resistance between front oxygen (A/F) sensor connector terminals.
Terminals 
No. 4 - No. 6: 		 Is the resistance less than 5 Ω? Go to step 5.  Replace the front oxygen (A/F) sensor. < Ref. to FRONT OXYGEN (A/F) SENSOR . >
5. CHECK POOR CONTACT. 
Check the poor contact in ECM and front oxygen (A/F) sensor connector.		 Is there poor contact in ECM or front oxygen (A/F) sensor connector? Repair the poor contact in ECM or front oxygen (A/F) sensor connector. Replace the front oxygen (A/F) sensor. < Ref. to FRONT OXYGEN (A/F) 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.