Circuit Description

WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The secondary air injection (AIR) valve relay controls high current to the AIR control solenoid valve/pressure sensor assembly. The AIR valve relay armature is held in the open position by spring tension. Ignition voltage is supplied to the AIR valve relay coil and armature when the key is in the ON position. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). One of the ODM output circuits is configured to operate as a low side driver for the AIR valve relay. The low side driver also incorporates a fault detection circuit, which is continuously monitored by the PCM. If the PCM detects a low side circuit fault, the driver will be turned OFF for the rest of the trip. The voltage on the control circuit should be battery voltage when the key is ON, and the AIR valve relay is at rest. If the fault detection circuit measures a low voltage under this condition, then an open or a short to ground on the control circuit or the ignition 1 voltage circuit, or an AIR valve relay coil fault may be present. If the PCM detects a low voltage on the control circuit when the AIR valve relay is commanded OFF, DTC P0412 will set.