Exhaust & Aftertreatment Systems and Diesel Service Procedures
Two technicians are discussing wide-band oxygen sensors on a newer diesel engine. Technician A says they are used to adjust the air-fuel ratio. Technician B says they are used to verify the operation of the EGR system. Which technician is correct?
Both technician A & B
Diesel exhaust fluid (DEF) is being discussed. Technician A says it includes distilled water. Technician B says it contains 32.5% urea. Which technician is correct?
Only technician B
What is the purpose of the restriction gauge on the air intake system?
to measure pressures that is less than atmospheric pressure; it will sense a restriction when the air filter needs to be replaced
How does a temperature sensor verify the operation of a diesel oxidation catalyst?
it monitors the function of various components
Why is it important to check the coolant nitrate level when checking the freeze protection and the acidity of the mixture?
nitrate levels protect iron and steel components
What type of information can be obtained by the service technician during the maintenance pre-check?
oil change intervals, DTCs, accident damage, and aftermarket items
Two technicians are discussing the maintenance pre-check that is performed prior to beginning routine service. Technician A says it is important to check for the presence of active and stored DTCs prior to beginning the service. Technician B says the information found in the maintenance pre-check must be recorded for future reference. Which technician is correct?
Both technicians A & B
Two technicians are discussing the nitrate level in the engine coolant. Technician A says the nitrate level can be checked with test strips. Technician B says that low nitrate levels may cause cylinder damage. Which technician is correct?
Both technicians A & B
Two technicians are discussing the service of the intake air filter. Technician A says the filter must be checked at ever engine service. Technician B says the filter must be replaced when the intake air restriction gauge indicates it is restricting air flow through the engine. Which technician is correct?
Both technicians A & B
The operation of a NOx adsorber catalyst is being discussed. Technician A says that the catalyst will not function properly unless the proper quality and quantity of diesel exhaust fluid is maintained. Technician B says the catalyst oxidizes the NOx emission during lean operating conditions. Which technician is correct?
Only technician B
The operation of a particulate filter is being discussed. Technician A says that it is designed to reduce NOx emissions. Technician B says that the filter is designed to trap particulate matter (PM). Which technician is correct?
Only technician B
Two technicians are discussing cooling system service. Technician A says the type of coolant in the engine can be identified by its color. Technician B says only deionized water may be used when diluting concentrated coolant. Which technician is correct?
Only technician B
The implementation of Tier II diesel emissions requirements in 2007 required the reduction of which two tailpipe emissions?
PM and NOx
The NOx sensor downstream of the selective catalyst induction (SCR) system fails to a minimum change in NOx in the exhaust stream. What could be the cause?
The SCR has failed; the DEF is of poor quality
The service technician is replacing the fuel filters on a light-duty diesel vehicle and the vehicle fails to restart after the task is completed. What is the most likely cause?
The filters were installed incorrectly, blocking the flow of fuel to the engine
During an active regeneration event:
The temperature of the DPF will be higher than during a passive regeneration event; will only occur if a passive regeneration event is ineffective; Additional fuel will be added to the DPF
During the service of a modern light-duty vehicle, the service technician finds the low DEF indicator illuminated. After refilling the system, the service technician notices the light is still illuminated. What is most likely cause of this condition?
This is normal operation
Diesel oxidation catalysts (DOC) are being discussed. Technician A says they are used to reduce the level of hydrocarbons (HC) in the exhaust stream. Technician B says they are used to reduce the level of carbon monoxide (CO) in the exhaust stream. Which technician is correct?
Both technician A & B
Two technicians are discussing the cooling system service. Technician A says it is important to check the secondary cooling system, as well as the primary cooling system. Technician B says to check the service information because some newer coolant may be backwards compatible. Which technician is correct?
Both technicians A & B
What is the difference between a passive and an active regeneration event?
a passive event normally occurs; an active event happens if a passive event cannot reduce the level of particulate in the filter
What is likely to occur if the driver fails to refill the diesel exhaust fluid reservoir?
a service engine soon light may illuminate and a fault code will be stored
How does the PCM use the pressure differential sensor to determine if the diesel particulate filter has a restriction?
compares pressure at the inlet and outlet of the DPF
During maintenance pre-check, the service technician finds the oil level in the engine to be overfull. What could cause this condition?
diesel fuel contamination; a leaking coolant system; overfill during a previous service
Temperature sensors are used to monitor the operation of the ____.
diesel particulate filter and DOC; NOx adsorber catalyst
Why must a "CJ-4" rated oil be used on a 2007 or newer vehicle equipped with a diesel engine?
low-ash oil
What happens if the customer fails to maintain the diesel exhaust fluid (DEF) at a minimum level?
the engine will not start
What is the role of an O2 sensor (if equipped) in the exhaust aftertreatment system?
to monitor the oxygen level in the exhaust stream
A wide-band oxygen sensor differs from a conventional oxygen sensor because ____.
It is able to a monitor a broader air-fuel ratio; it operates at a hotter temperature; it becomes operational faster on a cold start
Which of the following is the engine oil used in a 2007-2016 model year light-duty diesel vehicle?
CJ-4
During the service of a light-duty diesel vehicle, the service technician finds the water-in-fuel (WIF) indicator illuminated. How should this condition be resolved?
Drain the water separator
