Circuit Description
WARNING: This page is about a different car, the 2003 Isuzu Axiom. However, it is still accessible from the selected car via links, so may be relevant.
The input/output devices in the PCM include analog-to-digital converters, signal buffers, counters, and special drivers. The PCM controls most components with electronic switches which complete a ground circuit when turned ON. These switches are arranged in groups of 4 and 7, called either a surface-mounted Quad Driver Module (QDM), which can independently control up to 4 output terminals, or QDMs which can independently control up to 7 outputs.