Air Pump Check Valve

Air Pump Check Valve Operation:

A one-way valve that lets air flow from the air pump to the exhaust system. It's usually located in-line between the diverter valve and the air injection reactor (AIR) pipes in the cylinder head/exhaust manifold ports. It keeps exhaust gases from entering the air injection system.

Automotive Glossary
Check out one of the largest dictionaries of automotive terms
on the internet.