DTC P0418 Secondary Air Injection System Control "A" Circuit: 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: Secondary Air Injection System Control "A" - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSIS PROCEDURE

Step	Check	Yes	No
1 CHECK HARNESS BETWEEN ECM AND SECONDARY AIR PUMP RELAY CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Remove the secondary air pump relay. Measure the resistance of harness between ECM and secondary air pump relay connector. Connector & terminal (B135) No. 27 - (F9) No. 13:	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 secondary air pump relay connector Poor contact of coupling connector
2 CHECK HARNESS BETWEEN ECM AND SECONDARY AIR PUMP RELAY CONNECTOR. Measure the resistance between ECM and chassis ground. Connector & terminal (B135) No. 27 - Chassis ground:	Is the resistance 1 MΩ or more?	Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again. NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.	Repair the short circuit to ground in harness between ECM and secondary air pump relay connector.