OBD II, “CHECK-ENGINE” LIGHTS, and READINESS MONITORS..WHAT ARE THEY?
OBD II is a system that has been installed in most 1996 and later cars and light trucks, intended to inform the driver of problems in the components that control the engine and transmission. The primary reason OBD II was invented is to reduce smog emissions caused by malfunctions, but it is also valuable as an alert to the driver that something is wrong…something that can affect gas mileage and drivability, or actually cause further damage to the vehicle.