Air Injection: Description and Operation

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 components:
^ The 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. The filter is the only serviceable part of the pump.
^ The AIR vacuum control solenoid-The AIR vacuum control solenoid controls the AIR shut-off valve. When the secondary air injection 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.
^ The AIR shut-off valve-The AIR shut-off valve is vacuum operated. When the secondary air injection 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 valves.
^ The check valves-The check valves prevent back flow of exhaust gases into the secondary air injection 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.
^ The 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 air (oxygen) flow enters the exhaust stream, the start-up emission levels will rise. The control module can detect a system flow problem using the pre-catalyst HO2S and short-term Fuel Trim (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 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 DTCs can set if a secondary air injection fault is detected:
^ P0410- A system flow problem has been detected.
^ P0412-A vacuum control solenoid control circuit problem has been detected.
^ P0418- A pump relay control circuit problem has been detected.
^ P1415-A Bank 1 flow problem has been detected.
^ P1416-A Bank 2 flow problem has been detected.