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

WARNING: This page is about a different variant/trim than selected.

Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) Ref. to the appropriate SYSTEM WIRING diagram article. ENGINE TYPE EJ (WITHOUT PUSH BUTTON START).
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) Ref. to the appropriate SYSTEM WIRING diagram article. ENGINE TYPE EJ (WITH PUSH BUTTON START).

Fig 1: Engine Electrical System - Wiring Diagram (Engine Type EJ)
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. Start and warm up the engine. Turn the ignition switch to OFF. Disconnect the connectors from ECM and front oxygen (A/F) sensor. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector. Connector & terminal (B136) No. 5 - (B379) No. 2: (B136) No. 6 - (B379) No. 2: (B136) No. 18 - (B379) No. 3: (B136) No. 19 - (B379) No. 4:	Is the resistance less than 1 Ω?	Go to step 2.	Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
2 CHECK FRONT OXYGEN (A/F) SENSOR. Measure the resistance between front oxygen (A/F) sensor terminals. Terminals No. 1 - No. 2:	Is the resistance less than 2 - 3Ω?	Go to step 3.	Replace the front oxygen (A/F) sensor. < Ref. to FRONT OXYGEN (A/F) SENSOR . >
3 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?	Repair the poor contact of ECM or front oxygen (A/F) sensor connector.	Replace the front oxygen (A/F) sensor. < Ref. to FRONT OXYGEN (A/F) SENSOR . >