Air Injection: Description and Operation

PURPOSE
Emissions Control
The secondary Air Injection Reaction (AIR) management system is used on some engines to reduce Carbon Monoxide (CO) and Hydrocarbon (HC).

Promotes Combustion
The secondary AIR system, under certain conditions, adds air (oxygen) to the exhaust manifold to continue oxidation after the exhaust gases have left the combustion chamber. The heat from this reaction brings the three way catalytic converter up to operating temperature faster when the engine is cold.

AIR System (Type 1 -Belt Drive Air Pump- With V08 Option):

BELT DRIVEN PUMP
System Components
This system consists of an air pump, secondary air injection bypass valve with solenoid, check valve, and necessary plumbing.

Air Pump
A belt driven air pump supplies air through a centrifugal filter fan to the bypass valve. The shape of the centrifugal filter fan blades and the direction of fan rotation prevents foreign material from entering the pump with the incoming air.

Check Valve
The check valve on the air injection pipe, prevents back flow of exhaust gases into the air pump.

Bypass Valve
The bypass valve directs the air to either the engine exhaust manifold ports or to atmosphere. The bypass valve provides an air divert function to atmosphere for converter protection. When the Engine Control Module (ECM) decides a divert is desirable, it de-energizes the solenoid preventing manifold vacuum from entering the vacuum chamber.

^ At Wide Open Throttle (WOT), there is not enough intake manifold vacuum to compress the spring, so air is diverted.
^ At higher engine speeds, excess air is exhausted through the pressure relief valve or the divertor relief tube.

Air from the AIR pump is always shut "OFF" to the exhaust ports unless the ECM provides the ground for the bypass valve circuit (solenoid energized) which allows air flow to the exhaust ports.

AIR System (Type 2 - Electric Air Pump - Without V08 Option):

ELECTRIC AIR PUMP
System Components
This system consists of an electric AIR pump, internal switching valve, check valve and necessary plumbing.

Air Pump Control
The electric air pump operation is controlled by the ECM. The ECM will turn "ON" the electric air pump by providing the ground to complete the circuit which energizes the electric air pump relay.

Open Loop Operation
When air to the exhaust ports is desired, the ECM turns "ON" the air pump. The ECM enables the electric air pump after start-up any time engine cooling temperature is above 20°C (68°F). The pump will operate for a maximum of 240 seconds or until system enters "Closed Loop" operation.

Air Pump Idle Time
The air pump will be disabled when:

^ When the ECM recognizes a problem and sets a Diagnostic Trouble Code (DTC).
^ When the fuel system is operating in "Closed Loop."
^ Coolant temperature is between 20°C and 60°C (68°F and 140°F) and the electric air pump has been "ON" for 240 seconds.
^ Coolant temperature is above 60°C (140°F) and the electric air pump has been on for 30 seconds.
^ Engine speed greater than 1900 rpm.