Definitions of Aftertreatment System (ATS) Terms

The exhaust system must be free of leaks, binding, grounding, and excessive vibrations. In addition to inspecting the exhaust system at the scheduled maintenance interval, inspect the exhaust system if the noise level of the vehicle has increased. Replace parts that show leakage, wear, or damage, with genuine Freightliner parts.

These conditions are usually caused by loose, broken, or misaligned clamps, brackets, or pipes. If any of these conditions exist, check the exhaust system components and alignment. Align or replace as necessary. For alignment or adjustment instructions, see  of the Shuttle Bus Chassis Workshop Manual, or take the vehicle to an authorized Freightliner dealer.

Refer to the following list of definitions of ATS terms and components.

• Aftertreatment System (ATS)—the entire exhaust system from the turbocharger to the tail pipe, including the Selective Catalytic Reduction (SCR) components.

• Aftertreatment Device (ATD)—a device that removes pollutants from exhaust gas after the gas leaves the combustion chamber.

• BlueTec®—Daimler's proprietary SCR technology.

• Diesel Oxidation Catalyst (DOC)—a flow-through device that enhances the oxidation of hydrocarbons in the ATD.

• Diesel Particulate Filter (DPF)—a component in the ATD that traps particulate matter from the exhaust gas.

• Diesel Exhaust Fluid (DEF)—the chemical agent that reacts with the exhaust gases in the SCR to reduce NOx.

• DEF Pump—filters and supplies DEF to the DEF metering unit.

• DEF Tank—holds DEF and regulates its temperature.

• DEF Metering Unit—mixes DEF with compressed air, and meters this mixture into the exhaust flow via an injection nozzle.

• SCR Catalyst—the housing containing a treated ceramic flow-through block where the DEF and exhaust gases undergo selective catalytic reduction.

• Selective Catalytic Reduction (SCR)—a process used to reduce NOx emissions.