Circuit Description

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The secondary air injection (AIR) pump relay controls high current to the AIR pump. The AIR pump relay armature is held in the open position by spring tension. Ignition voltage is supplied to the AIR pump relay coil when the ignition is ON. Battery positive voltage is supplied to the armature contacts at all times. 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 pump relay. The low side driver also incorporates a fault detection circuit that is continuously monitored by the PCM. If the PCM detects a low side driver 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 ignition is ON and the AIR pump relay is at rest. If the fault detection circuit measures a low voltage under this condition, then an open, a short to ground on the control or the ignition 1 circuits or an open AIR pump relay coil fault may be present. If the PCM detects low voltage on the AIR pump relay control circuit when the AIR pump relay is commanded OFF, DTC P0418 will set.