The Secondary Air Injection (AIR) System reduces exhaust emissions following initial engine start
up. This occurs when the engine Start-up coolant temperature is between 3-50°C (37-122°F) and
the intake air temperature (IAT) is more than 1°C (32°F). The AIR pump will operate until Closed
Loop operation is achieved.

The powertrain control module (PCM) activates the AIR system by suppling a ground to the AIR
pump relay and AIR solenoid relay simultaneously. This action closes the internal contacts of the
AIR pump relay, energizing the AIR pump and also closes the internal contacts of the AIR solenoid
relay, energizing the AIR solenoid, opening the shut-off valve. The AIR pump forces pressurized
fresh air into the pipes/hoses and past the check valve into the exhaust manifold, accelerating
catalyst operation. When the AIR system is inactive, the AIR shut-off valve prevents airflow in either

The AIR diverter valve has an electronic solenoid mounted on the valve. The resistance of the
solenoid is 4-7 ohms and the current draw is 2-3.5 amps. The solenoid opens the shut-off valve
when battery voltage is applied to the valve. Once opened, pressurized air from the AIR pump flows
past the check valve and is directed into the exhaust manifold through an outlet pipe. The shut-off
valve prevents fresh air from being drawn into the exhaust manifold by providing a positive seal
when the AIR system is inactive. The solenoid, valve, and outlet pipe are serviced as an assembly.
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Engine Operation
2.2L  3100 / 3400 
3.5L  3800 
4200  4.3L Vortec

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Secondary Air Injection and Valve Operation