Air Injection: Description and Operation

AIR Management System Operation:

SYSTEM OPERATION
An Air Injection Reaction (AIR) system is used to provide additional oxygen to the exhaust stream outside of the combustion chamber. The additional oxygen allows the combustion process to continue to help reduce exhaust emissions. The AIR system uses an engine driven pump to inject air into either the exhaust manifold, the catalytic converter, or the air cleaner. The AIR system includes an Air Pump, two Check Valves, a Control Valve Assembly, and all necessary plumbing.

AIR PUMP
The AIR pump is driven by the serpentine belt on the front of the engine and supplies fresh air to the system. It is a positive displacement vane type which is permanently lubricated and requires no periodic maintenance. Filtered intake air is supplied to the pump by a hose attached to the air cleaner assembly. Air flows from the pump through two ECM controlled valves to either the exhaust manifold, catalytic converter, or the air cleaner.

CHECK VALVES
Check valves are one way valves which protect the air pump from damage by preventing a back flow of exhaust gas from the exhaust manifold or the catalytic converter.

CONTROL VALVE ASSEMBLY
The control valve assembly combines both the divert function and the air switching function in one housing. The air control valve provides air divert to the air cleaner for converter protection or directs air to the switching valve. The air switching valve directs the air to the exhaust manifold during cold engine operation. It directs air to the converter bed when the system is in closed loop. When divert is needed, the ECM turns off the divert solenoid in the air control valve assembly, forcing air to be diverted to the air cleaner.

NOTE:
Export vehicles only possess the switching portion of the valve. The valve directs air to the exhaust manifold during cold engine operation. Otherwise, the air is sent to the air cleaner.

AIR Management Hose Routing:

Air is diverted to the air cleaner under the following conditions:

1. Rich operation.

2. Under those conditions when the ECM recognizes a problem and sets the "SERVICE ENGINE SOON" or "SERVICE VEHICLE SOON" messages and the code is one which disables air management.

3. During deceleration to avoid backfiring in the catalytic converter.

4. During high RPM operation when air pressure is greater than the setting for the internal relief valve.

5. Under extremely cold weather starting conditions.

Air is diverted to the exhaust manifold when both the air switch and the air divert solenoids are energized.
Air is sent to the exhaust manifold when:

1. Coolant is below a warm operation limit.

2. Coolant is warm, but a timer after restarting the engine hasn't expired.

Air is diverted to the catalytic converter when the AIR switch solenoid is deenergized and the AIR divert solenoid is energized. Air will be sent to the converter if:

1. Not diverting or switched to manifold.

2. Coolant is greater than a minimum specified standard.