Truck & Transport Mechanic Certification and Maintenance Practice Test

The main idea is that the ECM coordinates engine and aftertreatment operations to keep exhaust emissions within legal limits. It uses sensor data from oxygen sensors, exhaust temperatures, flow and pressure sensors, and, in some systems, NOx sensors to adjust fuel delivery, ignition timing, EGR flow, and aftertreatment dosing. This keeps pollutants like NOx, CO, hydrocarbons, and particulates below the required specifications and helps the catalysts operate at their effective temperatures. While better fuel economy can come from efficient calibration, the primary objective is regulatory compliance. Cabin comfort and increasing exhaust noise aren’t the focus of emission control.