Secondary Air Injection (AIR) System Description

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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 direction.

The AIR system includes the following components:

The AIR pump
The AIR pump supplies pressurized, filtered air to the exhaust stream. The AIR pump is a turbine type pump which is permanently lubricated ad requires no periodic maintenance. The AIR pump for the 4.2 liter engine will draw a steady 35-40 amps under normal operation. The AIR pump has an internal circuit breaker to protect the pump from overheating. The circuit breaker is an integral part of the AIR pump.
The AIR shut-off valve
The AIR shut-off 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 bank 1 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.

IMPORTANT: An audible exhaust noise may be heard at the inlet of the shut-off valve, when the shut-off valve is opened and the AIR pump outlet hose is removed from the shut-off valve.
The AIR pump relay
The AIR pump relay supplies high current and battery voltage to the AIR pump. The resistance of the AIR pump relay coil is 55- 68 ohms.
The AIR solenoid relay
The AIR solenoid relay supplies high current and battery voltage to the AIR solenoid that is an integral part of the shut-off valve. The PCM commands the AIR solenoid relay ON by suppling a ground on the control circuit of the relay. The resistance of the AIR pump relay coil is 80-90 ohms.
The pipes and hoses
The pipes/hoses carry the air from the AIR pump past the AIR shut-off valve, and into the exhaust manifold. A pipe connects the shut-off valve to the exhaust manifold. The AIR System also utilizes a hose to carry the filtered air to the inlet of the AIR pump.
The inlet filter
The filter utilizes the air filter for the engine. This system draws filtered air directly from the air cleaner assembly.