Circuit Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The secondary air injection (AIR) pump relay controls the high current flow to the AIR pump. 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) controls the relay by supplying a ground path to the relay coil control circuit by an internal integrated circuit called an output driver module (ODM). The low side driver also incorporates a fault detection circuit that is continuously monitored by the PCM. 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 it is an indication of an open or short to ground on the control or ignition 1 circuits. An open AIR pump relay coil fault may also be present. If the PCM detects low voltage on the AIR pump relay control circuit when the AIR pump relay is commanded OFF or a high voltage when the AIR pump relay is commanded ON, DTC P0418 sets.