Air Injection: Description and Operation

OBD II The Secondary Air Injection System:

PURPOSE
The Secondary Air Injection (AIR) system controls HC and CO emissions during the first 20 to 120 seconds of engine operation. The AIR system forces air downstream into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start-up.

OPERATION
When the engine is started, the Powertrain Control Module (PCM) signals the solid state relay and the Secondary Air Bypass (AIRB) solenoid, after a few seconds delay, to begin system operation. The solid state relay provides the start-up signal and switches the high current required to operate the Electric Air Pump (EAP). The EAP provides air until the catalyst is lit-off and can oxidize and reduce emissions. The air injection solenoid applies a vacuum to the AIRD valve(s) causing it to open allowing air to flow into the exhaust manifold through the inlet. Once the catalyst is lit-off, the PCM signals the solid state relay to stop pump operation and the air injection solenoid to stop the vacuum supply to the AIRD valve(s).

CONSTRUCTION
The AIR system consists of an Electric Air Pump (EAP), a combination check and Air Diverter (AIRD) valve(s), an Air Injection Bypass (AIRB) solenoid, a solid state relay, Powertrain Control Module (PCM) and connecting wires and vacuum hoses. The inlet contains a splash cap that prevents dirt and water from entering the EAP.