Air Injection: Description and Operation

AIR System Schematic:

AIR System Components:

PURPOSE
The Air Injection Reaction (AIR) system helps reduce Hydrocarbons (HC), Carbon Monoxide (CO) and Oxides of Nitrogen (NOx) exhaust emissions.

The AIR system also helps to heat the catalytic converter quickly on engine start up so conversion of exhaust gases can occur sooner. When exhaust exits the engine, the excess hydrocarbons are burned with the fresh air supplied by the AIR system, which helps to heat the catalytic converter on cold start-up.

AIR System Electric Air Pump And Relay Circuit Diagram:

ELECTRIC AIR PUMP - DESCRIPTION
The electric air pump draws fresh filtered air from the air cleaner assembly and pumps it to the exhaust system through the air pipe and check valve assembly. The pump is PCM controlled through use of the air pump relay. During cold starts when the temperature is greater than 15°C (595°F), the PCM energizes the relay, turning the air pump and integral stop valve "ON". When the pump is operating, the integral stop valve is open to the exhaust system, and air is pumped into the exhaust manifolds to help oxidize excess hydrocarbons exiting the engine

ELECTRIC AIR PUMP - OPERATION
The air pump relay gets ignition voltage when the key is turned "ON" and becomes energized when the PCM completes the driver circuit to ground. When the relay is energized, a switch in the relay connects battery power to the air pump and stop valve solenoid in the pump, turning the pump and stop valve "ON". When the fuel system goes into "CLOSED LOOP" operation, or when the air pump has been running for a maximum of 240 seconds, the relay is de-energized and the AIR system is turned "OFF". When the pump is "OFF", the stop valve is also turned "OFF" and residual air pressure is diverted to the atmosphere while the pump spins down.


EXHAUST CHECK VALVES
The exhaust check valves prevent back flow of exhaust gases into the AIR system when the system is not operating.