Connecticut Heavy-Duty Vehicle Technician
Exam Practice Questions And Correct
Answers (Verified Answers) Plus Rationale |
Instant Download Pdf.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
150 exam-style multiple-choice questions. Each question includes the correct answer and a complete
rationale for focused revision.
COVERAGE
This exam assesses the knowledge and skills required for heavy-duty vehicle technicians in Connecticut,
covering diesel engine systems, electrical/electronic diagnostics, brake systems, suspension, HVAC, and
regulatory compliance. It emphasizes practical application, safety, and current industry standards.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 80%.
HIGHP - Page 1 of 49
,1. A heavy-duty truck equipped with an EPA 2010-compliant diesel engine exhibits
excessive black smoke and reduced power. A technician observes that the diesel
particulate filter (DPF) differential pressure sensor reads 0 psi at all times. Which of the
following is the most likely cause?
[ ] A. Failed DPF differential pressure sensor
[ ] B. Clogged DPF
[ ] C. Faulty exhaust gas recirculation (EGR) valve
[ ] D. Turbocharger overboost
CORRECT: A. Failed DPF differential pressure sensor
A constant 0 psi reading from the DPF differential pressure sensor indicates a sensor or circuit fault, not an
actual pressure condition. A clogged DPF would typically show elevated differential pressure. EGR and
turbocharger issues would not directly cause a zero DPF pressure reading.
2. When testing a heavy-duty vehicle's air brake system, a technician notes that the
low-pressure warning buzzer sounds at 60 psi. According to FMVSS 121, at what pressure
should the warning activate?
[ ] A. Below 60 psi
[ ] B. Between 60 and 80 psi
[ ] C. At or above 60 psi
[ ] D. Below 55 psi
CORRECT: C. At or above 60 psi
FMVSS 121 requires the low-pressure warning to activate at or above 60 psi. This ensures the driver is
alerted before pressure drops to a critical level. Options A, B, and D are inconsistent with the regulation.
3. A technician is diagnosing a no-start condition on a heavy-duty truck with a diesel
engine. The engine cranks but does not start. Which of the following diagnostic steps
should be performed FIRST?
[ ] A. Check for fault codes using a scan tool
[ ] B. Test fuel pressure at the secondary fuel filter
[ ] C. Inspect the fuel injector harness for damage
[ ] D. Perform a compression test
CORRECT: A. Check for fault codes using a scan tool
Retrieving fault codes is the most efficient first step as it can quickly identify electronic issues. Fuel pressure,
injector harness, and compression tests are more invasive and should follow if no codes are present. This
aligns with systematic diagnostic procedures.
HIGHP - Page 2 of 49
,4. In a heavy-duty vehicle with a 12-volt electrical system, a technician measures 10.5 volts
at the battery terminals while the engine is running at 1500 RPM. Which of the following is
the most likely cause?
[ ] A. Faulty alternator
[ ] B. Loose battery terminals
[ ] C. Shorted starter motor
[ ] D. Defective voltage regulator
CORRECT: A. Faulty alternator
A reading of 10.5 volts while running indicates the alternator is not charging properly. Loose terminals would
typically cause voltage drops under load, but a consistent low reading points to alternator failure. A shorted
starter would affect cranking, not running voltage.
5. A heavy-duty vehicle's suspension system uses air springs. The vehicle sits lower on
the left rear side. Which of the following is the most likely cause?
[ ] A. Leaking air spring
[ ] B. Faulty height control valve
[ ] C. Worn shock absorber
[ ] D. Broken leaf spring
CORRECT: A. Leaking air spring
A leaking air spring would cause that corner to sag. A faulty height control valve could affect both sides or the
entire axle. Worn shock absorbers do not affect ride height, and a broken leaf spring would not apply to an air
suspension system.
6. When servicing a heavy-duty vehicle's HVAC system, a technician finds that the air
conditioning compressor clutch does not engage. Which of the following is the most likely
cause?
[ ] A. Low refrigerant charge
[ ] B. Blown fuse for the compressor clutch
[ ] C. Faulty blower motor
[ ] D. Clogged cabin air filter
CORRECT: B. Blown fuse for the compressor clutch
A blown fuse would prevent power from reaching the compressor clutch, causing it not to engage. Low
refrigerant would typically be detected by pressure switches but would not directly prevent clutch
engagement if the system is designed to protect against low pressure. Blower motor and cabin filter issues
affect airflow, not clutch operation.
HIGHP - Page 3 of 49
, 7. A technician is performing a preventive maintenance inspection on a heavy-duty truck.
Which of the following components should be checked for proper operation of the engine
brake?
[ ] A. Exhaust gas recirculation valve
[ ] B. Turbocharger wastegate
[ ] C. Jake brake solenoid
[ ] D. Diesel particulate filter
CORRECT: C. Jake brake solenoid
The Jake brake (engine brake) uses solenoids to control oil flow to the engine brake mechanisms. Checking
the solenoid is essential for proper operation. EGR, turbo wastegate, and DPF are unrelated to engine brake
function.
8. A heavy-duty vehicle's automatic transmission is slipping in all forward gears. Which of
the following is the most likely cause?
[ ] A. Low transmission fluid level
[ ] B. Faulty torque converter clutch
[ ] C. Worn transmission mounts
[ ] D. Defective shift solenoid
CORRECT: A. Low transmission fluid level
Low fluid level can cause slipping in all gears due to insufficient hydraulic pressure. A faulty torque converter
clutch would typically affect lockup, not all gears. Worn mounts cause vibration, and a shift solenoid would
affect specific shifts.
9. When aligning a heavy-duty truck's front end, a technician measures the toe setting.
The specification is 1/16 inch toe-in. The measured value is 1/8 inch toe-out. Which of the
following adjustments is required?
[ ] A. Adjust tie rod ends to increase toe-in
[ ] B. Adjust tie rod ends to decrease toe-in
[ ] C. Adjust caster angle
[ ] D. Adjust camber angle
CORRECT: A. Adjust tie rod ends to increase toe-in
The measured toe is out of specification (toe-out instead of toe-in). To correct, the tie rod ends must be
adjusted to increase toe-in. Caster and camber adjustments affect different alignment angles.
10. A heavy-duty vehicle equipped with a selective catalytic reduction (SCR) system has a
fault code for DEF quality. Which of the following is the most appropriate action?
[ ] A. Replace the DEF filter
HIGHP - Page 4 of 49
Exam Practice Questions And Correct
Answers (Verified Answers) Plus Rationale |
Instant Download Pdf.
Practice Question Bank & Answer Rationale
THIS PACK CONTAINS
150 exam-style multiple-choice questions. Each question includes the correct answer and a complete
rationale for focused revision.
COVERAGE
This exam assesses the knowledge and skills required for heavy-duty vehicle technicians in Connecticut,
covering diesel engine systems, electrical/electronic diagnostics, brake systems, suspension, HVAC, and
regulatory compliance. It emphasizes practical application, safety, and current industry standards.
STUDY GUIDE
Recommended duration: 2 hours. Passing target: 80%.
HIGHP - Page 1 of 49
,1. A heavy-duty truck equipped with an EPA 2010-compliant diesel engine exhibits
excessive black smoke and reduced power. A technician observes that the diesel
particulate filter (DPF) differential pressure sensor reads 0 psi at all times. Which of the
following is the most likely cause?
[ ] A. Failed DPF differential pressure sensor
[ ] B. Clogged DPF
[ ] C. Faulty exhaust gas recirculation (EGR) valve
[ ] D. Turbocharger overboost
CORRECT: A. Failed DPF differential pressure sensor
A constant 0 psi reading from the DPF differential pressure sensor indicates a sensor or circuit fault, not an
actual pressure condition. A clogged DPF would typically show elevated differential pressure. EGR and
turbocharger issues would not directly cause a zero DPF pressure reading.
2. When testing a heavy-duty vehicle's air brake system, a technician notes that the
low-pressure warning buzzer sounds at 60 psi. According to FMVSS 121, at what pressure
should the warning activate?
[ ] A. Below 60 psi
[ ] B. Between 60 and 80 psi
[ ] C. At or above 60 psi
[ ] D. Below 55 psi
CORRECT: C. At or above 60 psi
FMVSS 121 requires the low-pressure warning to activate at or above 60 psi. This ensures the driver is
alerted before pressure drops to a critical level. Options A, B, and D are inconsistent with the regulation.
3. A technician is diagnosing a no-start condition on a heavy-duty truck with a diesel
engine. The engine cranks but does not start. Which of the following diagnostic steps
should be performed FIRST?
[ ] A. Check for fault codes using a scan tool
[ ] B. Test fuel pressure at the secondary fuel filter
[ ] C. Inspect the fuel injector harness for damage
[ ] D. Perform a compression test
CORRECT: A. Check for fault codes using a scan tool
Retrieving fault codes is the most efficient first step as it can quickly identify electronic issues. Fuel pressure,
injector harness, and compression tests are more invasive and should follow if no codes are present. This
aligns with systematic diagnostic procedures.
HIGHP - Page 2 of 49
,4. In a heavy-duty vehicle with a 12-volt electrical system, a technician measures 10.5 volts
at the battery terminals while the engine is running at 1500 RPM. Which of the following is
the most likely cause?
[ ] A. Faulty alternator
[ ] B. Loose battery terminals
[ ] C. Shorted starter motor
[ ] D. Defective voltage regulator
CORRECT: A. Faulty alternator
A reading of 10.5 volts while running indicates the alternator is not charging properly. Loose terminals would
typically cause voltage drops under load, but a consistent low reading points to alternator failure. A shorted
starter would affect cranking, not running voltage.
5. A heavy-duty vehicle's suspension system uses air springs. The vehicle sits lower on
the left rear side. Which of the following is the most likely cause?
[ ] A. Leaking air spring
[ ] B. Faulty height control valve
[ ] C. Worn shock absorber
[ ] D. Broken leaf spring
CORRECT: A. Leaking air spring
A leaking air spring would cause that corner to sag. A faulty height control valve could affect both sides or the
entire axle. Worn shock absorbers do not affect ride height, and a broken leaf spring would not apply to an air
suspension system.
6. When servicing a heavy-duty vehicle's HVAC system, a technician finds that the air
conditioning compressor clutch does not engage. Which of the following is the most likely
cause?
[ ] A. Low refrigerant charge
[ ] B. Blown fuse for the compressor clutch
[ ] C. Faulty blower motor
[ ] D. Clogged cabin air filter
CORRECT: B. Blown fuse for the compressor clutch
A blown fuse would prevent power from reaching the compressor clutch, causing it not to engage. Low
refrigerant would typically be detected by pressure switches but would not directly prevent clutch
engagement if the system is designed to protect against low pressure. Blower motor and cabin filter issues
affect airflow, not clutch operation.
HIGHP - Page 3 of 49
, 7. A technician is performing a preventive maintenance inspection on a heavy-duty truck.
Which of the following components should be checked for proper operation of the engine
brake?
[ ] A. Exhaust gas recirculation valve
[ ] B. Turbocharger wastegate
[ ] C. Jake brake solenoid
[ ] D. Diesel particulate filter
CORRECT: C. Jake brake solenoid
The Jake brake (engine brake) uses solenoids to control oil flow to the engine brake mechanisms. Checking
the solenoid is essential for proper operation. EGR, turbo wastegate, and DPF are unrelated to engine brake
function.
8. A heavy-duty vehicle's automatic transmission is slipping in all forward gears. Which of
the following is the most likely cause?
[ ] A. Low transmission fluid level
[ ] B. Faulty torque converter clutch
[ ] C. Worn transmission mounts
[ ] D. Defective shift solenoid
CORRECT: A. Low transmission fluid level
Low fluid level can cause slipping in all gears due to insufficient hydraulic pressure. A faulty torque converter
clutch would typically affect lockup, not all gears. Worn mounts cause vibration, and a shift solenoid would
affect specific shifts.
9. When aligning a heavy-duty truck's front end, a technician measures the toe setting.
The specification is 1/16 inch toe-in. The measured value is 1/8 inch toe-out. Which of the
following adjustments is required?
[ ] A. Adjust tie rod ends to increase toe-in
[ ] B. Adjust tie rod ends to decrease toe-in
[ ] C. Adjust caster angle
[ ] D. Adjust camber angle
CORRECT: A. Adjust tie rod ends to increase toe-in
The measured toe is out of specification (toe-out instead of toe-in). To correct, the tie rod ends must be
adjusted to increase toe-in. Caster and camber adjustments affect different alignment angles.
10. A heavy-duty vehicle equipped with a selective catalytic reduction (SCR) system has a
fault code for DEF quality. Which of the following is the most appropriate action?
[ ] A. Replace the DEF filter
HIGHP - Page 4 of 49
