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

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: HO2S Heater Control - Wiring Diagram (Bank 1 Sensor 1)

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSIS 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-(E23) No. 1: (B136) No. 6 - (E23) No. 1: (B136) No. 19 - (E23) No. 3: (B136) No. 18-(E23) 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 . >