DTC P0030: A/F/O2 Heater Control Circuit Bank 1 Sensor 1: Notes

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>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. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

G13202378

Courtesy of SUBARU OF AMERICA, INC.

CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR (OPEN).
1. Start and warm up the engine.
2. Turn the ignition switch to OFF.
3. Disconnect the connector from ECM.
4. Disconnect the connector from the front oxygen (A/F) sensor.
5. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector.
  Connector and terminal.
  
  (E158) No. 43 - (E24) No. 1:
  
  (E158) No. 65 - (E24) No. 2:
  
  (E158) No. 56 - (E24) No. 4:
  
  (E158) No. 44 - (E24) No. 5:
Is the resistance less than 1 Ω?

Yes : Go to 2.

No : Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
CHECK FRONT OXYGEN (A/F) SENSOR.
Check the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FRONT OXYGEN (A/F) SENSOR>INSPECTION .

Is the check result OK?

Yes : Go to 3.

No : Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FRONT OXYGEN (A/F) SENSOR .
CHECK FOR POOR CONTACT.
Check for poor contact of ECM and front oxygen (A/F) sensor connector.

Is there poor contact of ECM or front oxygen (A/F) sensor connector?

Yes : Repair the poor contact of ECM or front oxygen (A/F) sensor connector.

No : Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FRONT OXYGEN (A/F) SENSOR .