On-board diagnostic (OBD) systems monitor the performance of engine and aftertreatment components, including those responsible for controlling emissions.
1 The OBD system is designed to help ensure proper operation of the emission control equipment, alerting the driver in case of malfunctions, so that vehicles meet emissions limits during everyday use. OBD systems are a valuable tool for vehicle owners and technicians, as they supply important feedback about engine maintenance needs and point toward
potentially urgent repairs.