Air Injection: Description and Operation

The Secondary Air Injection (AIR) system is designed to help in the reduction of HC and CO emissions, by supplying additional oxygen into the exhaust system. This allows the hot exhaust gases to continue the combustion process of remaining unburned air/fuel charge, or to begin oxidizing HC and CO emissions.

Managed Thermactor Air System Operation:

The system supplies additional air from an air pump to a bypass valve, which either directs the air to a diverter valve or to the atmosphere, via a "dumping" action. Air supplied to the diverter valve is either directed upstream to the exhaust manifold or downstream to the catalytic converter.
Valve operation is controlled by internal diaphragms, and dependent upon manifold vacuum, which is supplied and regulated by computer controlled solenoid valves.

During cold engine warm-up, secondary air is routed to the exhaust manifold. The secondary air is needed to help continue the combustion process of a rich air/fuel mixture. Also, this action helps the catalytic converter to reach its operating temperature quicker.

After the engine and catalytic converter warm-up, the Powertrain Control Module (PCM) deenergizes the Secondary Air Injection Diverter (AIRD) solenoid (Secondary Air Injection Bypass (AIRB) remains energized) to direct secondary air to the catalytic converter. This allows the converter to operate at peak efficiency in its oxidation process.

Upon vehicle deceleration, the PCM deenergizes the AIRB Solenoid and secondary air is dumped to the atmosphere. This prevents engine backfires within the exhaust system.