Diesel engines can create noises that may seem concerning. The nature of a diesel engine is compression ignition where compressed air and fuel are mixed and ignited. Weather, barometric pressure, altitude, and temperature will affect how fuel is ignited in the engine. Engines will sound different from day to day or previous model years. Clicking, ticking, or light knocking is normal and will change from day to day, as the engine breaks in, and can vary with changes in ambient temperature. Clicking sound from under the hood shortly after vehicle shutdown is normal as actuators such as the EGR valve are cycled. Fuel pump noise may increase during low speed/light load conditions when ambient temperature is above 100°F (38°C), and when fuel tank level is below 10% which is a normal condition of the fuel system and controls strategy. Diesel equipped vehicles also have an exhaust after-treatment system to reduce emissions utilizing a Diesel Particulate Filter (DPF) and a Selective Reduction Catalyst (SCR). The SCR reduces Nitrogen Oxides (NOx) using the Diesel Exhaust Fluid (DEF) system. DEF is injected directly into the SCR through a dosing module. This process will create a clicking sound and at times, will make noise even with the vehicle shut off. This is normal as the DEF dosing module is purging DEF. If at any time the Check Engine Light is on, please visit an authorized dealer.