Possible causes

– Faulty Vacuum hoses damaged
– Faulty Air Pump inoperative
– Air bypass solenoid harness is open or shorted
– Air bypass solenoid circuit poor electrical connection
– Air bypass solenoid leaking/blocked or stuck open/closed
– Air diverter valve leaking/blocked or stuck open/closed

When is the code detected?

The secondary air injection system does not detect the presence of air in the exhaust when introduced by the secondary air injection system.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Engine hesitation

P0411 SUBARU Description

An air pump is used on the vehicle to lower tail pipe emissions on start-up. The Powertrain Control Module (PCM) grounds the Air pump relay control circuit which energizes the Air pump. The PCM also grounds the Air combination valve vacuum control solenoid circuit, which energizes the Air vacuum control solenoid. Vacuum is then applied to both Air combination valve diaphragms which opens the shut off valves. The PCM enables both circuits simultaneously when Air system operations id desired. When the AIR system is active, then Air pump forces fresh air into the exhaust stream in order to accelerate catalyst operation. The AIR combination valves replace the conventional check valves. When the AIR system is inactive the shut off valves prevent air flow in either direction.