The secondary air injection (AIR) system is used on the 7.4L to reduce carbon monoxide (CO) and hydrocarbons (HC).

The AIR system adds air (oxygen) to the exhaust manifold to continue oxidation after the exhaust gasses have left the combustion chamber. The heat from this reaction brings the catalytic converter up to operating temperature faster when the engine is cold.

This system consists of an AIR pump, VCM controlled electronic clutch, check valves, and necessary plumbing.

A belt driven AIR pump supplies filtered air from the air intake system to the AIR injection pipes.

The check valves, on the AIR injection pipes, prevent backflow of exhaust gasses in the AIR pump.

When the engine is started with a coolant temperature above approximately 15°C (45°F) or if the fuel system is in the Decel Mode, the VCM energizes the AIR relay. The AIR relay then energizes the AIR clutch, which directs air into the exhaust manifold ports.

The control module may turn the AIR pump OFF when any of the following conditions occur: