Air Injection: Description and Operation

DESCRIPTION
The Secondary Air Injection System (AIR) aids in the reduction of first and second cycle hydrocarbon emissions. During open-loop fuel control, air is injected into the exhaust stream for a specified amount 9f time. Heat generated from post-combustion oxidation helps the catalytic converter reach operating temperature sooner (referred to as converter light off). The following conditions determine pump operation and run time:

^ Start up ECT and IAT must be between 15°C - 110°C (59°F - 230°F).
^ If ECT sensor signal indicates an engine temperature greater than 70°C, total pump ON time is 40 seconds.
^ If ECT sensor signal indicates an engine temperature less than 70°C, total pump ON time is 100 seconds.

OPERATION
The Secondary Air Injection Reaction (AIR) system is controlled by the PCM. During open loop fuel control, the PCM energizes the AIR system relay. Battery voltage is supplied to the AIR pump, internal shut-off valve, and bleed-off valve for maximum of 100 seconds on a cold start and 40 seconds on a hot restart. Air from a remotely mounted filter is drawn into the pump by centrifugal action, pressurized, and pumped through check valves into the exhaust stream. Without the bleed-off valve, a vacuum would build in the AIR hoses due to the venturi effect created as the exhaust gases flow past the injection piping. The vacuum is strong enough to hold the internal shut-off valve closed. To prevent this situation, the bleed-off valve vents the vacuum to atmosphere. An inline check valve prevents air from escaping through the bleed-off valve during injection. Check valves in the AIR piping to each cylinder bank prevent exhaust backflow when AIR is commanded OFF or an exhaust backfire occurs.

RESULTS OF INCORRECT AIR SYSTEM OPERATION
If, during open loop fuel control, air injection isn't present in the exhaust stream, high first and second hydrocarbon emissions result.
Continuous air injection to the exhaust stream will result in the following condition(s):

^ DTC P0131 and/or P0410 will set.
^ Open loop fuel control will be in effect.
^ Backfiring in the exhaust/catalyst system may occur.
^ Catalyst damage may occur.

No air injection to the exhaust stream will result in the following condition(s):

^ DTC P0410 will set.
^ High Hydrocarbon and Carbon monoxide emissions will occur during open loop fuel control.