Air Injection: Description and Operation

A.I.R. System Operation:

A.I.R. System:

PURPOSE
The Air Injection Reaction (AIR) system supplies fresh air to the exhaust manifolds during start-up at certain temperatures, to help oxidize unburned hydrocarbons as they exit the engine. This also helps to bring the catalytic converters and oxygen sensors up to operating temperature more quickly.

Electric Air Pump:

A.I.R. Bypass Valve:

OPERATION
Air is supplied by the electric air pump located in front of the left front wheel housing. The ECM controls operation of the electric air pump relay which turns the air pump "ON" and "OFF". The AIR Bypass Solenoid solenoid controls the AIR Bypass (divert) valve, which directs air from the air pump to the exhaust ports or diverts air to the atmosphere when the system is turned "OFF". This is so air to the exhaust ports is shut off while the air pump is spinning down. One-way check valves allow air into the exhaust system while preventing exhaust gas from escaping through the AIR system.

The electric air pump relay and AIR Bypass valve solenoid get battery power when the ignition is turned "ON", and become energized when the ECM completes the circuits to ground. When energized, the relay turns the air pump "ON" and the AIR Bypass valve directs pump air to the exhaust ports. The ECM will energize the solenoid and the air pump relay together during start up when the coolant temperature is between 15°C/59°F and 65°C/149°F. The ECM operates the solenoid and air pump relay for a maximum of 150 seconds, or until the ECM switches to closed loop operation. If the engine temperature is above 65°C/149°F at start-up, the ECM will operate the AIR Bypass valve solenoid and air pump for a maximum of 25 seconds.