Secondary Air Injection Systems

The Secondary Air Injection (AIR) system controls emissions during the first 20 to 120 seconds of engine operation by forcing air downstream into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.

Dual Or Single AIRD Valve Electric Secondary Air Injection (AIR):

ELECTRIC SECONDARY AIR INJECTION SYSTEM
The Electric Secondary Air Injection (AIR) system consists of an electric AIR pump, single or dual combination check air injection diverter (AIR diverter) valve(s), an AIR bypass solenoid, a solid state relay, Powertrain Control Module (PCM) and connecting wires and vacuum hoses.

1. The PCM requires ECT, IAT and CKP inputs to initiate Secondary Air Injection function.
2. When the engine is started, the strategy will determine when to enable the EAP. The PCM signals the solid state relay and the AIR bypass solenoid, after a [5 to 10] second delay, to begin system operation. Once the catalyst is lit-off, the PCM then signals the solid state relay to stop AIR pump operation and the AIR bypass solenoid to stop the vacuum supply to the AIR diverter valve(s).
3. The solid state relay provides the start-up signal and will switch the high current required to operate the AIR pump.
4. The AIR bypass solenoid applies a vacuum to the AIR diverter valve(s) causing it to open and to allow air to flow into the exhaust manifolds.
5. The function of the splash cap if equipped is to provide the AIR pump with a source of dry air.
6. The electric AIR pump delivers the required amount of air to control emissions during engine operation. Air is forced into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.

HARDWARE

Electric Air Pump:

Electric AIR Pump
The electric AIR pump provides pressurized air to the Secondary Air Injection system. The electric AIR pump functions independently of rpm and is controlled by the PCM. The electric AIR pump is only used for short periods of time. Delivery of air is dependent on the amount of system backpressure and system voltage. The inlet system of the AIR pump incorporates a non-serviceable filter and splash cap which helps to guard against dirt and water.





AIR Bypass Solenoid
The secondary air injection bypass (AIR bypass) solenoid is used by the PCM to control vacuum to the secondary Air Injection Diverter (AIR diverter) valve. The AIR bypass solenoid is a normally closed solenoid. The AIR bypass solenoid also has a filtered vent feature to permit vacuum release.





AIR Diverter Valve
The secondary Air Injection Diverter (AIR diverter) valve is used with the electric AIR pump to provide ON/OFF control of air to the exhaust manifold and catalytic converter. When the electric AIR pump is ON and vacuum is supplied to the AIR diverter valve, air passes the integral check valve disk. When the electric AIR pump is OFF, and vacuum is removed from the AIR diverter valve, the integral check valve disk is held on the seat and stops air from being drawn into the exhaust system and prevents the back flow of the exhaust into the Secondary Air Injection System.





Solid State Relay
The solid state relay 4 pin or 5 pin design switches the high current required for operation of the electric AIR pump. Input control to the solid state relay comes from the Powertrain Control Module (PCM).





BELT-DRIVEN SECONDARY AIR INJECTION SYSTEM
The Belt-Driven Secondary Air Injection system consists of a belt-driven AIR pump, single or dual AIR diverter valve(s), an AIR bypass valve, and AIR bypass solenoids, AIR silencer/filter, powertrain control module and connecting wires and vacuum hoses. The Belt-Driven Secondary Air Injection system provides either upstream/bypass air or upstream/downstream/bypass air. The number of these system configurations vary significantly with AIR bypass and AIR diverter valve combinations.

1. The PCM requires ECT, IAT and CKP inputs to initiate secondary air injection operation.
2. The PCM provides one or more signals that enable one or more AIR bypass solenoids.
3. The AIR bypass solenoids control one or more AIR bypass valves and/or AIR bypass diverter valves in order to route secondary air depending upon the specific configuration.
4. The belt-driven AIR pump is operational any time the engine is running.





AIR Pump
The AIR pump is a belt-driven, positive displacement. vane-type pump that provides air for the Secondary Air Injection system. It is available in 19 and 22 cubic inch sizes, either of which may be driven with different pulley ratios for different applications. AIR pumps receive air from a remote silencer filter, the clean air side of the engine air cleaner attached to the pump's air inlet nipple, or an impeller type centrifugal filter fan.





AIR Silencer
The AIR silencer is a combination silencer and filter for AIR pumps. The AIR silencer is mounted in the engine compartment and is connected to the AIR pump inlet by a flexible hose.





AIR Check Valve
The AIR check valve is a one-way valve that allows secondary air to pass into the exhaust system while preventing exhaust gases from passing in the opposite direction.

Normally Closed AIR Bypass Valves
The AIR bypass valves are normally closed valves which supply air to the exhaust system with medium and high applied vacuum signals during normal (engine at normal operating temperature) modes. With low or no vacuum applied, the pumped air is dumped through the silencer ports of the valve or through the dump port.





Normally Open AIR Diverter Valves
The AIR diverter valve is used as a valve, directing air to the catalyst/exhaust system or to a remote air dump location depending on engine control strategy.





Normally Closed AIR Bypass Solenoid
The normally closed secondary AIR injection bypass solenoid assembly consists of two vacuum ports with an atmospheric vent. The solenoid assembly can be with or without control bleed. The outlet port of the solenoid is opened to atmospheric vent and closed to the inlet port when de-energized. When energized, the outlet port is opened to the inlet port and closed to atmospheric vent. The control bleed is provided to prevent contamination from entering the solenoid assembly from the intake manifold.

Dual AIR Bypass and AIR Diverter Solenoids

NOTE: The solenoids can be expected to have a very small leakage rate when energized or deenergized. This leakage is not measurable in the field and is not detrimental to solenoid function.





The dual secondary AIR control solenoid assembly contains two normally closed vacuum solenoids. One solenoid controls the AIR bypass valve and the other solenoid controls the AIR diverter valve. Both solenoids vent when de-energized and are supplied by the intake manifold vacuum and controlled by the Powertrain Control Module (PCM).





Vacuum Check Valves
A vacuum check valve blocks air flow in one direction. It allows free air flow in the other direction. The check side of this valve will hold the highest vacuum registered on the vacuum side.





Vacuum Reservoirs
The vacuum reservoir stores vacuum and provides "muscle" vacuum. It prevents rapid fluctuations or sudden drops in a vacuum signal such as during an acceleration period.