Secondary Air Injection System Description: Notes

The secondary air injection (AIR) system aids in the reduction of hydrocarbon exhaust emissions during a cold start-up. This occurs when the start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F), and the intake air temperature (IAT) is between 5-60°C (41-140°F). The AIR pump operates 5-60 seconds after start-up.

The engine control module (ECM) activates the AIR system by simultaneously supplying grounds to the AIR pump and the AIR valve relays. This action closes the relays' internal contacts. The AIR pump and the AIR control solenoid valve/pressure sensor assembly are in turn energized, the pump runs and the control/shut-off valve opens.

The AIR pump sends pressurized fresh air into the pipes/hoses through the open control/shut-off valve, and into the exhaust manifold. The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The AIR pump remains ON for a short period of time after the control/shut-off valve is commanded OFF. When the AIR pump is commanded OFF it will not run or be activated until the next vehicle start. When the AIR system is inactive, the closed AIR control/shut-off valve prevents air/exhaust flow in either direction.

The AIR system pressure sensor is used to monitor pressure at the AIR control solenoid valve/pressure sensor assembly inlet during the commanded ON/OFF states.

The AIR system includes the following components:

• The AIR pump-The electric AIR pump supplies pressurized, filtered air to the AIR control/shut-off valve. The AIR pump is a turbine type pump that is permanently lubricated and requires no periodic maintenance.
IMPORTANT: The AIR solenoid, control/shut-off valve, and the pressure sensor are serviced as an assembly.
• The AIR solenoid-The AIR solenoids opens the AIR control/shut-off valve when the solenoid is energized by the AIR solenoid relay.
IMPORTANT: An audible exhaust or fluttering noise may be heard at the control solenoid valve/pressure sensor assembly inlet when the valve is open and the AIR hose is removed from the control solenoid valve/pressure sensor assembly.
• The AIR control solenoid valve/pressure sensor assembly-The AIR control solenoid valve/pressure sensor assembly has a solenoid mounted valve. When the valve is open by the solenoid, pressurized air from the AIR pump flows through the control solenoid valve/pressure sensor assembly and is directed into the exhaust manifold through an outlet pipe.
• The AIR pressure sensor-The AIR pressure sensor is a part of the AIR control solenoid valve/pressure sensor assembly. The sensor is a 3-wire sensor that measures the AIR system pressure at the AIR control solenoid valve/pressure sensor assembly inlet.
• The AIR pump relay-The AIR pump relay supplies high current and battery voltage to the AIR pump. The ECM commands the relay ON by supplying a ground to the relay control circuit.
• The AIR valve relay-The AIR valve relay supplies high current and battery voltage to the AIR solenoid. the ECM commands the relay ON by supplying a ground to the relay control circuit.
• The pipes and hoses-The AIR system hose carries filtered air from the engine air cleaner to the AIR pump inlet. The pipe/hoses carry the air from the AIR pump to the AIR control solenoid valve/pressure sensor assembly and on to the exhaust manifold.
• The inlet filter-The AIR system does not have a separate inlet air filter. Filtered air is drawn from the engine air cleaner assembly.