Certificate Of Qualification Truck And Coach
Technician (310T) Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a diesel particulate filter (DPF)?
A. Increase exhaust noise
B. Reduce nitrogen oxides
C. Trap and burn soot particles
D. Cool exhaust gases
Answer: C
The DPF captures soot and periodically regenerates to burn it off.
2. What condition most commonly triggers active DPF regeneration?
A. High coolant temperature
B. Excessive soot load
C. Low oil pressure
D. High turbo boost
Answer: B
Active regeneration begins when soot accumulation reaches a
calibrated level.
3. Which sensor is used to monitor DPF restriction?
A. MAP sensor
B. EGT sensor
C. Differential pressure sensor
D. Oxygen sensor
, Answer: C
Differential pressure across the DPF indicates soot loading.
4. What is the function of an SCR system?
A. Reduce particulate matter
B. Reduce hydrocarbons
C. Reduce NOx emissions
D. Increase exhaust temperature
Answer: C
Selective Catalytic Reduction lowers nitrogen oxides using DEF.
5. Diesel Exhaust Fluid (DEF) is primarily composed of:
A. Methanol and water
B. Urea and deionized water
C. Ethanol and additives
D. Ammonia and coolant
Answer: B
DEF is 32.5% urea and 67.5% deionized water.
6. A failed NOx sensor will most likely cause:
A. Engine overspeed
B. Reduced engine power
C. Transmission slipping
D. Loss of coolant
Answer: B
Emission faults commonly trigger derate or limp mode.
7. What does excessive black smoke indicate?
A. Lean air-fuel mixture
B. Excess fuel or lack of air
C. Cool combustion
, D. High exhaust restriction only
Answer: B
Black smoke results from incomplete combustion due to rich
mixture.
8. Blue exhaust smoke usually indicates:
A. Coolant burning
B. Excess fuel
C. Oil consumption
D. DPF regeneration
Answer: C
Blue smoke is caused by engine oil entering the combustion
chamber.
9. White smoke on cold start is often caused by:
A. Oil burning
B. Excess air
C. Unburned fuel
D. High exhaust temperature
Answer: C
Cold cylinders can cause incomplete combustion.
10. What component supplies high-pressure fuel to common rail
injectors?
A. Lift pump
B. Injection pump
C. High-pressure pump
D. Fuel return valve
Answer: C
The high-pressure pump generates rail pressure.
Technician (310T) Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. What is the primary purpose of a diesel particulate filter (DPF)?
A. Increase exhaust noise
B. Reduce nitrogen oxides
C. Trap and burn soot particles
D. Cool exhaust gases
Answer: C
The DPF captures soot and periodically regenerates to burn it off.
2. What condition most commonly triggers active DPF regeneration?
A. High coolant temperature
B. Excessive soot load
C. Low oil pressure
D. High turbo boost
Answer: B
Active regeneration begins when soot accumulation reaches a
calibrated level.
3. Which sensor is used to monitor DPF restriction?
A. MAP sensor
B. EGT sensor
C. Differential pressure sensor
D. Oxygen sensor
, Answer: C
Differential pressure across the DPF indicates soot loading.
4. What is the function of an SCR system?
A. Reduce particulate matter
B. Reduce hydrocarbons
C. Reduce NOx emissions
D. Increase exhaust temperature
Answer: C
Selective Catalytic Reduction lowers nitrogen oxides using DEF.
5. Diesel Exhaust Fluid (DEF) is primarily composed of:
A. Methanol and water
B. Urea and deionized water
C. Ethanol and additives
D. Ammonia and coolant
Answer: B
DEF is 32.5% urea and 67.5% deionized water.
6. A failed NOx sensor will most likely cause:
A. Engine overspeed
B. Reduced engine power
C. Transmission slipping
D. Loss of coolant
Answer: B
Emission faults commonly trigger derate or limp mode.
7. What does excessive black smoke indicate?
A. Lean air-fuel mixture
B. Excess fuel or lack of air
C. Cool combustion
, D. High exhaust restriction only
Answer: B
Black smoke results from incomplete combustion due to rich
mixture.
8. Blue exhaust smoke usually indicates:
A. Coolant burning
B. Excess fuel
C. Oil consumption
D. DPF regeneration
Answer: C
Blue smoke is caused by engine oil entering the combustion
chamber.
9. White smoke on cold start is often caused by:
A. Oil burning
B. Excess air
C. Unburned fuel
D. High exhaust temperature
Answer: C
Cold cylinders can cause incomplete combustion.
10. What component supplies high-pressure fuel to common rail
injectors?
A. Lift pump
B. Injection pump
C. High-pressure pump
D. Fuel return valve
Answer: C
The high-pressure pump generates rail pressure.
