Air Injection: Description and Operation

A.I.R. System Operation:

SYSTEM DESCRIPTION

This system is used to reduce Carbon Monoxide (CO), Hydrocarbon (HC), and Nitrous Oxide (NOx) emissions. It also assists in the heating of the catalytic converter on engine start-up. This allows the conversion of exhaust gases to begin much sooner.

A single bed, three-way catalyst, monolith type converter is used for each cylinder bank. It consists of a three-way catalyst to control all three emissions. Air can be directed to the exhaust ports or to the atmosphere.

A.I.R. System:

Electric Air Pump:

The A.I.R. system includes:

1. An Electric Air Pump:
The electric air pump is located in the left front corner of the underhood compartment. Inlet air passes through an inlet silencer at the front of the pump. The electric pump pressurizes the air and sends it to the control valve.

CAUTION: Mask off the inlet air silencer whenever pressure washing or steam cleaning the engine compartment to prevent damage to the air pump.

2. Control Valve (EDV):
The control valve directs the flow of air from the electric air pump to the exhaust ports or to the atmosphere.
3. Control (EDV) Solenoid:
The Electric Divert Valve Solenoid is normally closed and controls vacuum to an internal valve which performs a switching operation by direction air flow from the electric air pump to the exhaust ports (solenoid energized) or to the atmosphere (solenoid de-energized). The ECM provides the ground to complete the circuit and energize the EDV solenoid. The electric air pump relay and Electric Divert Valve solenoid are energized simultaneously by the ECM.
4. Check Valves:
The check valves prevent back flow of exhaust into the pump in the event of an exhaust backfire.
5. Necessary plumbing.

A.I.R. Bypass Valve:

ELECTRIC DIVERT VALVE DESCRIPTION

The electric air pump operation and EDV solenoid are controlled by the ECM. The ECM will turn on the electric air pump by providing the ground to energize the air pump relay. The EDV solenoid is also energized when the ECM provides the ground.
When air to the exhaust ports is desired, the ECM turns on both the electric air pump and the EDV solenoid. The ECM turns on the electric air pump after start-up any time coolant temperature is between 15~C and 65~C (57~F and 149~F), the electric air pump will operate for a maximum of 80 seconds, or until the system enters "Closed Loop" operation. If the coolant temperature is above 65~C(149~F), the electric air pump will operate for a maximum of 25 seconds, or until the system enters "Closed-Loop" operation. At the same time the ECM turns the electric air pump off, it also de-energizes the EDV solenoid and switches the EDV to the divert mode.

The air is diverted to the atmosphere under the following conditions:

^When the ECM recognizes a problem and sets a diagnostic code.
^When the fuel system is operating in closed loop.
^When the coolant temperature is between 15~C and 65~C (57~F and 149~F) and the electric air pump has been on for 80 seconds.
^When the coolant temperature is above 65~C (149~F) and the electric air pump has been on for 25 seconds.