DTC P0418: Secondary Air Injection System Relay Circuit: Description

AIR system is used to accelerate the heating process of the catalytic converters by introducing outside air into the exhaust system. Air pump operates on cold engine starts. PCM controls the air pump by controlling the ground for the air pump relay coil. PCM monitors relay coil circuit for low and high voltage faults. DTC will set when air pump relay is commanded off and feedback voltage at PCM is low.