Secondary Air Injection System Description
The secondary air injection (AIR) system helps reduce exhaust emissions. The system forces fresh filtered air into the exhaust stream in order to accelerate catalyst operation.
The system includes the following:
| • | AIR pump --The AIR pump supplies filtered air through the secondary air injection system into the exhaust stream. The control module provides ground for the pump relay, battery voltage is then applied to the pump. |
| • | AIR vacuum control solenoid --The AIR vacuum control solenoid controls the AIR shut-off valve. When the AIR system is enabled, the control module provides a ground to the solenoid. Enabling the solenoid allows engine vacuum to be 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 to the check valve. |
| • | Check valve --The check valve prevents back flow of exhaust gases into the AIR system. An AIR pump that had become inoperative and had shown indications of having exhaust gases in the outlet port would indicate check valve failure. |
| • | Plumbing --The plumbing carries the air from the pump to the exhaust stream. The plumbing includes the hoses, pipes and clamps. The plumbing 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 no airflow enters the exhaust stream, the start up emission levels will rise. The control module can detect a system flow problem using the pre catalyst heated oxygen sensor (HO2S) and Short term FT. If a system flow problem is present the HO2S voltage will not indicate an expected lean condition, Short Term FT will not increase and a diagnostic trouble code (DTC) will set.
If incorrect voltage is present on the vacuum control solenoid or the pump relay control circuits the device will not operate. This will be detected by the control module and a DTC will set.
The following DTC will scan if a AIR fault is detected: DTC P0410 -- A system flow problem has been detected.
