Air Injection: Description and Operation
Typical AIR System:
LEGEND
(1) AIR Pump
(2) AIR Check Valve
(3) Exhaust Manifold
(4) Exhaust Manifold
(5) Check Valve
(6) AIR Injection Pipe
(7) Intake Manifold
(8) AIR Injection Pipe
(9) AIR Bleed Valve Solenoid Valve
(10) Air to Exhaust Ports
(11) Fresh Air Intake Pipe
DESCRIPTION
The Secondary Air Injection (AIR) system helps reduce Hydrocarbon (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx) exhaust emissions. It also heats up the warm up 3way catalytic converters quickly on engine start-up so conversion of exhaust gases can occur sooner.
COMPONENTS
The system includes the following:
^ AIR pump - The AIR pump is mounted to the lower left front of the engine Compartment and supplies the air to the AIR system. The electric air pump pressurizes air from the engine and pumps it to the check valves near the exhaust manifolds. The AIR pump is controlled by the PCM. Battery voltage to the AIR pump is controlled by the AIR pump relay. An integral stop valve prevents air flow through the pump during OFF periods. When the PCM provides a ground circuit for the secondary AIR pump relay, battery voltage is allowed to power up the AIR pump and integral stop valve.
^ Vacuum Bleed Valve - This valve helps prevent vacuum buildup within the AIR system, which could prevent the integral stop valve from opening. The bleed valve is controlled by the air pump relay and will be energized when the AIR pump is commanded ON. If the vacuum relief system is not functioning, the vacuum will cause the AIR pump integral valve not to open. This may result in no AIR flow to the exhaust manifolds or delay the delivery of air which may not allow the diagnostic to pass.
^ Check valves - The check valves prevent back flow of exhaust gases into the AIR pump in the event of an exhaust backfire.
^ Necessary plumbing.
- Hoses
- Pipes
- Clamps
OPERATION
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. When air to the exhaust ports is desired, the PCM turns ON both the integral stop valve and AIR pump.
The PCM turns ON the AIR pump during startup any time engine coolant temperature is above 15°C (59°F). The AIR pump will operate for a maximum of 240 seconds, or until the system enters Closed Loop operation. At the same time the PCM turns the AIR pump OFF, it also deenergizes the integral stop valve solenoid so no air is directed to the exhaust ports.
The air system will be disabled under the following conditions:
^ When the PCM recognizes a problem and sets a diagnostic trouble code.
^ When the fuel system is operating in Closed Loop.
^ The AIR pump has been ON for 240 seconds.
^ Engine Speed is greater than 2825 RPM.
^ MAP is greater than 96 kPa with VSS over 60 mph.
^ MAP is less than 20 kPa.
^ ECT less than -8.5°C (17°F).
^ Warm up 3-way catalytic converters over temperature detected.
^ Short and long term fuel trim are not in their normal ranges.
^ Power enrichment is detected.
RESULTS OF INCORRECT OPERATION
If no air (oxygen) flow enters the exhaust stream at the exhaust ports, HC and CO emission levels will be too high.
Air flowing to the exhaust ports at all times could increase temperature of the warm up away catalytic converter.
Diagnostic Trouble Codes P0410, P0412, P1415, and P1416 will set if there is a malfunction in the following components:
^ The AIR pump.
^ The AIR pump relay.
^ Hoses or pipes that are leaking.
^ The Check valves that are leaking.
^ Circuits going to the AIR pump and the AIR pump relay.
The vacuum bleed valve.