Secondary Air Injection System Description: Notes

The secondary air injection (AIR) pump system is designed to lower exhaust emission levels on engine start-up.

The powertrain control module (PCM) commands the AIR pump relay ON, by supplying a ground on the air pump relay control circuit. This action energizes the AIR pump forcing fresh air, oxygen, into the exhaust stream. The PCM also commands the secondary air injection (AIR) solenoid ON, by supplying a ground on the air solenoid control circuit. With the AIR solenoid activated engine vacuum is applied to the AIR shut-off valve. Fresh air from the AIR pump then enters into the exhaust stream, accelerating catalyst operation, reducing exhaust emission levels. When the AIR system is inactive, the AIR shut-off valve and the exhaust check valves prevent airflow in either direction.

The secondary air injection (AIR) system includes the following components:

• The AIR pump relay- The AIR pump relay supplies high current to the AIR pump. The PCM commands the AIR pump relay ON by suppling a ground on the control circuit of the relay. This action closes the internal contacts of the AIR pump relay, energizing the AIR pump.
• The AIR pump-The AIR pump supplies fresh air to the exhaust stream. The inlet hose and filter is the only serviceable part of the pump.
• The AIR injection solenoid-The AIR injection solenoid controls the AIR shut-off valve. When the AIR system is enabled, the PCM supplies a ground on the control circuit of the air solenoid. This enables the air solenoid, allowing engine vacuum to be applied to the AIR shut-off valve.
• The AIR shut-off valve-The AIR shut-off valve is vacuum operated. When the AIR system is enabled, engine vacuum is applied to the valve. The vacuum opens the shut-off valve allowing fresh air from the AIR pump to flow to the exhaust check valves. When inactive the shut-off valve prevents airflow in either direction.
• The exhaust check valves-The exhaust check valves prevent back flow of exhaust gases into the AIR system. A shut-off valve that has become inoperative, showing indications of exhaust gases in the outlet port, or heat damaged hoses may indicate an exhaust check valve failure.
• The pipes/hoses-The pipes/hoses carry the air from the AIR pump to the exhaust stream. The pipes/hoses can be tested for leaks using a soapy water solution, with the AIR pump running, bubbles will form if a leak exists.