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Diesel Mechanic Practice Test

Check what you know about the diesel mechanic job with 15 free questions and instant explanations.

Updated By the Career Education Institute Curriculum Team
About this practice test

15 multiple-choice questions on diesel mechanic knowledge, safety and vocabulary. Submit to see your score and explanations, or open any question’s answer as you go. Nothing is saved or shared.

Question 1 of 15What does a DPF do?
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Answer: Traps soot from exhaust. Diesel particulate filters capture soot.

Question 2 of 15DEF is used by which emissions system?
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Answer: SCR. SCR systems use DEF to reduce NOx.

Question 3 of 15How do diesel engines ignite fuel?
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Answer: Heat from compressed air. Diesels use compression ignition.

Question 4 of 15Before working under a truck you should:
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Answer: Chock wheels and use jack stands. Proper support prevents crushing injuries.

Question 5 of 15Excessive pushrod stroke indicates:
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Answer: Brakes out of adjustment. Over-stroke means brakes are out of adjustment.

Question 6 of 15Which term matches this definition: “Uses exhaust energy to compress intake air.”
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Answer: Turbocharger. Turbocharger: Uses exhaust energy to compress intake air.

Question 7 of 15What does “SPN / FMI” mean?
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Answer: Suspect parameter number and failure mode identifier: parts of heavy-duty fault codes.. SPN / FMI: Suspect parameter number and failure mode identifier: parts of heavy-duty fault codes.

Question 8 of 15Which term matches this definition: “Selective catalytic reduction: reduces nitrogen oxide emissions.”
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Answer: SCR. SCR: Selective catalytic reduction: reduces nitrogen oxide emissions.

Question 9 of 15What does “PM” mean?
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Answer: Preventive maintenance: scheduled service to prevent breakdowns.. PM: Preventive maintenance: scheduled service to prevent breakdowns.

Question 10 of 15Which term matches this definition: “Exhaust gas recirculation: returns some exhaust to the intake to lower emissions.”
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Answer: EGR. EGR: Exhaust gas recirculation: returns some exhaust to the intake to lower emissions.

Question 11 of 15What does “Compression ignition” mean?
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Answer: Diesel combustion where fuel ignites from the heat of compressed air.. Compression ignition: Diesel combustion where fuel ignites from the heat of compressed air.

Question 12 of 15Which term matches this definition: “Burning off soot collected in the DPF.”
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Answer: Regeneration (regen). Regeneration (regen): Burning off soot collected in the DPF.

Question 13 of 15What does “Air dryer” mean?
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Answer: Removes moisture from compressed air in brake systems.. Air dryer: Removes moisture from compressed air in brake systems.

Question 14 of 15Which term matches this definition: “The communication protocol used on heavy-duty vehicle networks.”
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Answer: J1939. J1939: The communication protocol used on heavy-duty vehicle networks.

Question 15 of 15What does “Pushrod stroke” mean?
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Answer: How far the brake chamber pushrod travels: used to check brake adjustment.. Pushrod stroke: How far the brake chamber pushrod travels: used to check brake adjustment.

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