Air Injection: Description and Operation

SECONDARY AIR INJECTION (AIR) SYSTEM DESCRIPTION







The Secondary Air Injection (AIR) system is designed to lower exhaust emissions. The system forces filtered air into the exhaust stream to accelerate catalyst operation. The air (oxygen) that is introduced into the catalyst helps decrease the time for the converter to begin the burning process of unburned hydrocarbons on cold or warm starts.

The system includes the following:
- AIR pump -The AIR pump supplies filtered air through the secondary air injection system into the exhaust stream. The Powertrain Control Module (PCM) supplies a ground to the AIR pump relay, battery voltage is then applied to the AIR pump.
- AIR vacuum control solenoid-The AIR vacuum control solenoid controls the AIR shut-off valve. When the AIR system is commanded ON by the PCM voltage is supplied to the solenoid by the AIR pump relay. When the AIR vacuum solenoid is commanded ON engine vacuum applied to the AIR shut-off valve.
- AIR shut-off valve -The AIR shut-off valve is vacuum operated. When the AIR system is enabled, vacuum is applied to the valve. The vacuum opens the valve and allows air from the AIR pump to flow through the check valve and into the exhaust stream.
- Check valve -The check valve prevents flow of exhaust gases into the AIR system. An AIR shut-off valve that has become inoperative and shows indications of having exhaust gases in the outlet port indicates a check valve failure and heat damage to the AIR crossover hose would be evident.
- Hoses/Pipes -The hoses/pipes carry the air from the AIR pump to the exhaust stream. The hoses/pipes can be tested for leaks using a soapy water solution. With the AIR pump running, bubbles with form if a leak exists.

Results Of Incorrect Operation
If airflow does not enter the exhaust stream, the start up emission levels will rise. The PCM can detect a system flow problem using the pre catalyst heated oxygen sensor (O2S). If an insufficient airflow problem is present the O2S voltage will not indicate an expected lean condition, and DTC P0410 sets.

If incorrect voltage is present on the vacuum control solenoid or the AIR pump relay control circuits the devices will not operate. This will be detected by the PCM as a no flow condition at the O2 sensor and DTC P0410 sets.