Circuit Description

WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) activates the secondary air injection (AIR) system by grounding the AIR relay. This energizes the pump and the vacuum control solenoid. As vacuum is applied to the shut-off valve, fresh air is allowed to pass through the pump and vacuum control solenoid. The AIR pump forces fresh air past the shut-off valve and into the exhaust stream in order to accelerate catalyst operation. The PCM will run up to 3 diagnostic tests using the O2S 1 voltage and short term FT to verify system operation. The system can be diagnosed during normal AIR operation or the scan tool can activate the system specifically for diagnostic purposes. If an airflow problem is detected this, DTC will set. When inactive, the shut-off valve prevents air flow in either direction.