Air Injection: Description and Operation

Secondary Air Injection System:

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

The AIR system heats the catalytic converter quickly on engine start up so conversion of exhaust gases can occur sooner.

A single bed three-way catalyst monolith converter is used to reduce all three emissions.

Secondary Air Injection (AIR) System:

OPERATION

Electric Air Pump
The Air Pump with integral stop valve is controlled by the PCM. The PCM will turn "ON" the air pump by providing the ground to complete the circuit which energizes the air pump relay.

The electric air pump supplies air to the AIR system. Intake air passes through an inlet silencer at the front of the pump. The air is then pressured and pumped to the control valve. The air pump is controlled by the PCM and is protected by a 20 amp fuse.

When air to the exhaust ports is desired, the PCM turns "ON" the air pump and the stop valve. This takes place at any time the engine coolant temperature is above -8.5°C (17°F). The air pump will operate for a maximum of 240 seconds, or until the system enters closed loop.

The air system will be disabled under the following conditions:

^ When PCM recognizes a diagnostic trouble code has been set
^ When fuel system is operating in "closed loop"
^ The air pump has been "ON" for 240 seconds
^ RPM is greater than 2825
^ MAP is greater than 96kPa with VSS over 60 mph
^ MAP is less than 20kPa
^ ECT is less than -8.5°C (17°F)
^ Catalytic overheat condition exists
^ Short or long term fuel trim are not in normal ranges
^ Power enrichment is detected


Check Valves
The check valves prevent back flow of exhaust gases into the pump in the event of an exhaust backfire.