Exam 18: Exhaust Aftertreatment Systems

What NOX aftertreatment does not require onboard storage of liquid DEF, instead, produces ammonia inside a unique catalyst substrate through a multistep chemical process that uses hydrogen from fuel molecules and nitrogen from stored NOx?

Trapped soot and other trapped particles collected on the walls of the DPF (diesel particulate filter) will eventually plug the filter and produce:

How many distinct stages of exhaust aftertreatment systems are used based on the progressively more restrictive Environmental Protection Agency (EPA) emission standards?

Two technicians are describing DEF (diesel exhaust fluid) operation. Technician A says that the amount of DEF used is in proportion to the amount of exhaust NOx. Technician B says that some DEF systems base the dosage on a probability of NOx in the exhaust system by using algorithms stored in the ECM. Who is right?

The fleet average benchmark for NOx in 2010 was no more than:

Technician A says that DEF is always evacuated from lines and valves after the vehicle has shut down to prevent DEF from crystalizing and plugging the SCR system. Technician B says that DEF is removed to prevent it from freezing and causing damage. Who is correct?

Which of the following procedures is used to control DEF (diesel exhaust fluid) dosing, formed between the NOx sensors, ammonia (NH3) sensors, an ECM, and the dosing valve in the latest systems?

The SCR reservoir of a 2010 pickup truck has been completely depleted for more than 10 hours of driving time and the engine power has derated. Technician A says the correct service recommendation is to fill the DEF reservoir and clear associated fault codes to return the vehicle to service and full power. Technician B says the correct procedure is to fill the DEF reservoir and prime the DEF lines to remove the derate condition. Who is correct?

The liquid that contains the urea is called DEF and is rich in:

After two technicians examine a broken and disintegrated DPF filter, Technician A says the filter damage was caused by water contamination. Technician B says the filter was damaged by back-to-back regenerations that occurred too frequently. Who is correct?

Which of the following is NOT a common exhaust catalyst element in the exhaust aftertreatment systems being used on contemporary diesel engines?

Dosing the exhaust system of a 2007 diesel engine with fuel is necessary to do which of the following?

Technician A says that once the DEF (diesel exhaust fluid) level becomes critical, vehicle speed will be limited. Technician B says that low DEF level display may be accompanied by a chime or voice message. Who is right?

Dosing the exhaust system of a 2007 diesel engine with fuel is necessary to do which of the following?

After two technicians examine a broken and disintegrated DPF filter, Technician A says the filter damage was caused by water contamination. Technician B says the filter was damaged by back-to-back regenerations that occurred too frequently. Who is correct?

Technician A says diesel exhaust oxidation catalysts used by diesel engines are like those used in automobiles for the last two decades. Technician B says diesel exhaust oxidation catalysts will store noxious emissions in the substrate when the exhaust temperatures are low. Who is correct?

Which of the following strategies is typically used to actively regenerate a catalyzed DPF?

When comparing types of catalytic technology used by diesel engines and spark-ignition engines, which of the following catalyst technologies reduces just NOx (oxides of nitrogen)?

The use of SCR and DPFs requires which type of fuel?

To extend DPF (diesel particulate filter) life caused by compacted ash and cracking, some fleets make it part of routine maintenance to remove and clean DPFs on a regular basis, more frequently than what is required by the: