Question 1

Which is the more popular method commonly used to remove NOx from diesel exhaust gases?

Accepted Answer

A) Selective catalyst reduction with urea (SCR-U)" 
B) NAC (nitrogen adsorbing catalysts)" 
C) Selective catalyst reduction with Hydrogen (SCR-H) 
D) LNT (lean NOxtTrap)" 
A) Selective catalyst reduction with urea (SCR-U)" 
B) NAC (nitrogen adsorbing catalysts)" 
C) Selective catalyst reduction with Hydrogen (SCR-H) 
D) LNT (lean NOxtTrap)"

Question 2

Technician A says the problem with using automobile catalysts in the exhaust system of diesel engines is the system's excess air and cool temperatures. Technician B says diesel exhaust catalysts need to be designed to withstand the higher exhaust temperatures of a diesel engine and its exhaust's lower oxygen content. Who is correct?

Accepted Answer

A) Technician A" 
B) Technician B" 
C) Both A and B 
D) Neither A nor B" 
A) Technician A" 
B) Technician B" 
C) Both A and B 
D) Neither A nor B"

Question 3

A DEF warning and power derate takes place if the DEF (diesel exhaust fluid) level is:

Accepted Answer

A) filled" 
B) changed" 
C) leaking 
D) depleted" 
A) filled" 
B) changed" 
C) leaking 
D) depleted"

Question 4

Which of the following is the function of an intake throttle valve on a diesel engine equipped with a DPF?

Accepted Answer

A) To increase exhaust backpressure. 
B) To increase exhaust temperature. 
C) To decrease cylinder EGR content. 
D) To increase engine retarding force when decelerating with compression release brakes. 
A) To increase exhaust backpressure. 
B) To increase exhaust temperature. 
C) To decrease cylinder EGR content. 
D) To increase engine retarding force when decelerating with compression release brakes.

Question 5

Which strategy will most likely be used to passively regenerate a catalyzed DPF?

Accepted Answer

A) A stationary vehicle with raised idle and a partially closed intake throttle. 
B) Using OEM software or a scanner to perform regeneration (light-duty vehicles only). 
C) Driving at speeds above 45 mph (72 kph) for a minimum of 20 minutes. 
D) Logging a fault code for a DPF with 80% or more soot loading. 
A) A stationary vehicle with raised idle and a partially closed intake throttle. 
B) Using OEM software or a scanner to perform regeneration (light-duty vehicles only). 
C) Driving at speeds above 45 mph (72 kph) for a minimum of 20 minutes. 
D) Logging a fault code for a DPF with 80% or more soot loading.

Question 6

Technician A says nitric oxide (NO) is used by the DPF to convert soot to harmless emissions. Technician B says that the SCR catalysts cause NO to be converted into harmless emissions. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 7

Which of the following is an in-cylinder method used by manufacturers to prevent emission formation?

Accepted Answer

A) DPF (diesel particulate filter)" 
B) SCR (selective catalyst reduction)" 
C) Oxidation catalyst 
D) EGR (exhaust gas recirculation)" 
A) DPF (diesel particulate filter)" 
B) SCR (selective catalyst reduction)" 
C) Oxidation catalyst 
D) EGR (exhaust gas recirculation)"

Question 8

Which of these DEF (diesel exhaust fluid) states of operation comes after the engine starts and circulates DEF throughout the system, but in which no dosing takes place?

Accepted Answer

A) Heating state" 
B) Priming state" 
C) Dosing state 
D) Purging state" 
A) Heating state" 
B) Priming state" 
C) Dosing state 
D) Purging state"

Question 9

Consider a 2018 school bus that has the DPF warning lamp illuminated. The amber light is on steadily. What is the most correct service recommendation?

Accepted Answer

A) Drive the vehicle under load at a moderate speed for 20-40 minutes. 
B) Use a dash switch to initiate a stationary regeneration. 
C) Use OEM software to initiate an active regeneration. 
D) Tow the vehicle to a service location and replace the
DPF) 
A) Drive the vehicle under load at a moderate speed for 20-40 minutes. 
B) Use a dash switch to initiate a stationary regeneration. 
C) Use OEM software to initiate an active regeneration. 
D) Tow the vehicle to a service location and replace the
DPF)

Question 10

Which of the following DEF (diesel exhaust fluid) system component is NOT incorporated into a single module?

Accepted Answer

A) DEF controller (ECM)" 
B) DEF-quality and DEF-level sensor" 
C) DEF pump and reverting valve 
D) DEF dosing valve" 
A) DEF controller (ECM)" 
B) DEF-quality and DEF-level sensor" 
C) DEF pump and reverting valve 
D) DEF dosing valve"

Question 11

Technician A recommends that customers have the DPF removed and cleaned once a year. Technician B says the DPF needs to be actively regenerated at every oil change. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 12

OEM rebuilders have observed a relationship between increased ash loading in DPF (diesel particulate filter) and the likelihood for a DPF to:

Accepted Answer

A) crack" 
B) plug" 
C) open up 
D) explode" 
A) crack" 
B) plug" 
C) open up 
D) explode"

Question 13

What are chemical reactions called where oxygen is removed from NOx?

Accepted Answer

A) Induction" 
B) Calcification" 
C) Reduction 
D) Oxidation" 
A) Induction" 
B) Calcification" 
C) Reduction 
D) Oxidation"

Question 14

Using SCR delivers which of the following?

Accepted Answer

A) Improved fuel economy and fewer DPF regenerations because injection timing is advanced. 
B) Improved fuel economy and fewer DPF regenerations because injection timing is retarded. 
C) Improved fuel economy and fewer DPF regenerations because DEF increases combustion efficiency. 
D) Only lower NOx emissions. 
A) Improved fuel economy and fewer DPF regenerations because injection timing is advanced. 
B) Improved fuel economy and fewer DPF regenerations because injection timing is retarded. 
C) Improved fuel economy and fewer DPF regenerations because DEF increases combustion efficiency. 
D) Only lower NOx emissions.

Question 15

Which process is used to clean ash from a DPF?

Accepted Answer

A) Active regeneration." 
B) Passive regeneration." 
C) Filter replacement. 
D) Removal and back-flushing with compressed air." 
A) Active regeneration." 
B) Passive regeneration." 
C) Filter replacement. 
D) Removal and back-flushing with compressed air."

Question 16

The DPF warning light and the red shutdown warning lamp are flashing. Technician A says the DPF filter needs to be removed and replaced. Technician B says the DPF needs an active regeneration. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 17

Technician A says that without the pressure differential sensor (delta P sensor), the exhaust DPF would not regenerate, because the amount of soot loading would not be able to be properly calculated. Technician B says that the amount of soot loading is only estimated, and not accurately measured, using the delta P sensor. Who is correct?

Accepted Answer

A) Technician A" 
B) Technician B" 
C) Both A and B 
D) Neither A nor B" 
A) Technician A" 
B) Technician B" 
C) Both A and B 
D) Neither A nor B"

Question 18

Which of the following causes oxygen to chemically combine with HC (hydrocarbons) and CO (carbon monoxide) at lower temperatures with the result of HC and CO being converted to carbon dioxide and water?

Accepted Answer

A) Oxidation catalytic converter" 
B) Reduction catalytic converter" 
C) DPF (diesel particulate filter) 
D) Selective catalytic reduction using liquid (SCR-L)" 
A) Oxidation catalytic converter" 
B) Reduction catalytic converter" 
C) DPF (diesel particulate filter) 
D) Selective catalytic reduction using liquid (SCR-L)"

Question 19

Two technicians are explaining SCR (selective catalyst reduction) operation. Technician A says that after the urea decomposes into ammonia in the mixing chamber, the ammonia-exhaust gas composition passes over an SCR catalyst containing either copper or iron to break apart NOx molecules. Technician B says that blades or screens in the mixing device are used to create exhaust gas turbulence ahead of the mixing chamber. Who is right?

Accepted Answer

A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B" 
A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B"

Question 20

Technician A says the problem with using automobile catalysts in the exhaust system of diesel engines is the system's excess air and cool temperatures. Technician B says diesel exhaust catalysts need to be designed to withstand the higher exhaust temperatures of a diesel engine and its exhaust's lower oxygen content. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Which is the more popular method commonly used to remove NOx from diesel exhaust gases?

A DEF warning and power derate takes place if the DEF (diesel exhaust fluid) level is:

Which of the following is the function of an intake throttle valve on a diesel engine equipped with a DPF?

Which strategy will most likely be used to passively regenerate a catalyzed DPF?

Technician A says nitric oxide (NO) is used by the DPF to convert soot to harmless emissions. Technician B says that the SCR catalysts cause NO to be converted into harmless emissions. Who is correct?

Which of the following is an in-cylinder method used by manufacturers to prevent emission formation?

Which of these DEF (diesel exhaust fluid) states of operation comes after the engine starts and circulates DEF throughout the system, but in which no dosing takes place?

Consider a 2018 school bus that has the DPF warning lamp illuminated. The amber light is on steadily. What is the most correct service recommendation?

Which of the following DEF (diesel exhaust fluid) system component is NOT incorporated into a single module?

Technician A recommends that customers have the DPF removed and cleaned once a year. Technician B says the DPF needs to be actively regenerated at every oil change. Who is correct?

OEM rebuilders have observed a relationship between increased ash loading in DPF (diesel particulate filter) and the likelihood for a DPF to:

What are chemical reactions called where oxygen is removed from NOx?

Using SCR delivers which of the following?

Which process is used to clean ash from a DPF?

The DPF warning light and the red shutdown warning lamp are flashing. Technician A says the DPF filter needs to be removed and replaced. Technician B says the DPF needs an active regeneration. Who is correct?

Which of the following causes oxygen to chemically combine with HC (hydrocarbons) and CO (carbon monoxide) at lower temperatures with the result of HC and CO being converted to carbon dioxide and water?

Introduction to Diesel Engines

Diesel Engine Emissions

Cylinder Blocks and Crankshafts

Cylinder Components

Cylinder Heads and Valve Train Mechanisms

Diesel Engine Cooling and Lubrication Systems

Diesel Fuel and Low Pressure Fuel Systems

Functions of High Pressure Fuel Systems

Governors and Electronic Control Systems

Hydraulic Nozzles

Heui Injection Systems

Common Rail Fuel Systems

Air Induction and Crankcase Ventilation Systems

Fixed Geometry and Wastegated Turbochargers

Variable Geometry and Series Turbochargers

Exhaust Gas Recirculation

On Board Diagnostics

Filters

Exam 18: Exhaust Aftertreatment Systems

Which is the more popular method commonly used to remove NOx from diesel exhaust gases?

A DEF warning and power derate takes place if the DEF (diesel exhaust fluid) level is:

Which of the following is the function of an intake throttle valve on a diesel engine equipped with a DPF?

Which strategy will most likely be used to passively regenerate a catalyzed DPF?

Technician A says nitric oxide (NO) is used by the DPF to convert soot to harmless emissions. Technician B says that the SCR catalysts cause NO to be converted into harmless emissions. Who is correct?

Which of the following is an in-cylinder method used by manufacturers to prevent emission formation?

Which of these DEF (diesel exhaust fluid) states of operation comes after the engine starts and circulates DEF throughout the system, but in which no dosing takes place?

Consider a 2018 school bus that has the DPF warning lamp illuminated. The amber light is on steadily. What is the most correct service recommendation?

Which of the following DEF (diesel exhaust fluid) system component is NOT incorporated into a single module?

Technician A recommends that customers have the DPF removed and cleaned once a year. Technician B says the DPF needs to be actively regenerated at every oil change. Who is correct?

OEM rebuilders have observed a relationship between increased ash loading in DPF (diesel particulate filter) and the likelihood for a DPF to:

What are chemical reactions called where oxygen is removed from NOx?

Using SCR delivers which of the following?

Which process is used to clean ash from a DPF?

The DPF warning light and the red shutdown warning lamp are flashing. Technician A says the DPF filter needs to be removed and replaced. Technician B says the DPF needs an active regeneration. Who is correct?

Which of the following causes oxygen to chemically combine with HC (hydrocarbons) and CO (carbon monoxide) at lower temperatures with the result of HC and CO being converted to carbon dioxide and water?

Introduction to Diesel Engines

Diesel Engine Emissions

Cylinder Blocks and Crankshafts

Cylinder Components

Cylinder Heads and Valve Train Mechanisms

Diesel Engine Cooling and Lubrication Systems

Diesel Fuel and Low Pressure Fuel Systems

Functions of High Pressure Fuel Systems

Governors and Electronic Control Systems

Hydraulic Nozzles

Heui Injection Systems

Common Rail Fuel Systems

Air Induction and Crankcase Ventilation Systems

Fixed Geometry and Wastegated Turbochargers

Variable Geometry and Series Turbochargers

Exhaust Gas Recirculation

On Board Diagnostics

Filters