DTC P0030 Ho2S Heater Control Circuit (Bank 1 Sensor 1): Wiring Diagram

Engine electrical system, 2.5 L model (without push button start). See appropriate SYSTEM WIRING DIAGRAM article.
Engine electrical system, 2.5 L model (with push button start). See appropriate SYSTEM WIRING DIAGRAM article.

Fig 1: Heater Control - Circuit Diagram (Bank 1 Sensor 1)
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 and front oxygen (A/F) sensor connector. Connector & terminal (B136) No. 5 - (E24) No. 1: (B136) No. 19 - (E24) No. 3: (B136) No. 18 - (E24) No. 4:	Is the resistance less than 1 Ω?	Go to step 2 .	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit in harness between ECM and front oxygen (A/F) sensor connector Poor contact of coupling 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 2 - 3 Ω?	Go to step 3 .	Replace the front oxygen (A/F) sensor. Refer 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. Refer to FRONT OXYGEN (A/F) SENSOR .