Secondary Air Injection System Description. Pontiac Vibe

The secondary air injection (AIR) system helps reduce exhaust emissions. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. The powertrain control module (PCM) commands the AIR pump ON when the engine is first start after a cold soak. On an engine that has sat overnight, the AIR pump can run for a maximum of 30 seconds.


(1)	Powertrain Control Module (PCM)
(2)	Secondary Air Injection (AIR) Shut-Off Valve
(3)	AIR Pressure Sensor
(4)	AIR Pump Relay
(5)	AIR Pump Assembly
(6)	AIR Pump Filter
(7)	AIR Pump
(8)	Exhaust Manifold Passage
(9)	Intake Manifold Passage
(10)	Vacuum Check Valve
(11)	AIR Solenoid Valve

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, then the battery voltage is applied to the pump. The filter is the only serviceable part of the pump.

•	The AIR solenoid valve--The AIR solenoid valve controls the vacuum supply to 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 the 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 exhaust manifold.

•	The AIR pressure sensor--The pressure sensor monitors the flow from the AIR pump. By comparing the measured pressure against the expected pressure the pressure sensor can detect faults in the AIR pump, AIR shut-off valve, and the AIR solenoid valve.

•	The vacuum check valve--The check valve prevents the loss of vacuum pressure to the shut off valve during times of reduced intake manifold pressure.

•	The plumbing--The plumbing carries the air from the pump to the exhaust stream. The plumbing includes the hoses, the pipes, and the clamps. You can test the plumbing for leaks using a soapy water solution. With the AIR pump running, the bubbles with form if a leak exists.

Results of Incorrect Operation

If no air flow enters the exhaust stream, the start-up emission levels will rise. The control module can detect a system flow problem using the pressure sensor, and a DTC will set.