Circuit Description

Input and output devices in the ECM include analog-to-digital converters, signal buffers, counters and special drivers. ECM controls most components with electronic switches which complete a ground circuit when switched On. Switches are arranged in groups of 4 and 7 called surface-mounted Quad Driver Modules (QDM), which independently control 4 or 7 outputs.

When DTC sets, ECM will not illuminate MIL. ECM will store conditions present when DTC was set as FAILURE RECORDS data only.

ECM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to ECM.