Air Injection System: Operation: Notes

The firing of the engine creates a pulsing flow of exhaust gases. Negative exhaust pressure (vacuum) causes one of the check valves to open, either upstream or downstream depending on operating conditions. In the exhaust system, this increase in the oxygen content reduces exhaust emissions.

Air supplied to the check valves is controlled by vacuum operated air control valves. The vacuum supply to the control valves is controlled by air switching solenoids. These solenoids, in turn, are controlled by the Electronic Control Unit (ECU).