S15/T15 Sonoma P/U 2WD L4-2.2L VIN 5 Flex Fuel (2001)
Air Injection Check Valve: Description and Operation
Secondary Air Injection (AIR) 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-oft 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.
AIR shut-off valve-The AIR shut-off valves are 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.
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.
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 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.
