Secondary Air Injection (AIR) System Description: Notes
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 5-80°C (41-176°F), and the intake air temperature (IAT) is more than 5°C (41°F). The AIR pump will operate until Closed Loop operation is achieved.
The powertrain control module (PCM) activates the AIR system by simultaneously suppling a ground to the AIR pump relay and the AIR solenoid relay. 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 shut-off valve into the bank 1 exhaust manifold, accelerating the 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 and requires no periodic maintenance. The AIR pump for the 4.6L engine will draw a steady 45-50 amps under normal operation.
- The AIR Shut-Off Valve-The AIR shut-off valve has an electronic solenoid mounted on the valve. The resistance of the solenoid is 4-6 ohms and the current draw is 2-3 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 shut-off valve and is directed into the bank 1 exhaust manifold through an outlet pipe. The shut-off valve contains an internal check valve that 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.
- 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 65-75 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 solenoid relay coil is 75-85 ohms.
- Pipes and Hoses-The pipes/hoses carry the air from the AIR pump past the AIR check valve and into the exhaust manifold. A pipe connects the check 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-There are 2 types of inlet filters. The first type utilizes the air filter for the engine. This system draws filtered air directly from the air cleaner assembly. The second type uses a separate filter that provides filtered air exclusively for the AIR system.