Oklahoma Medium/Heavy Truck
Technician Assessment Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which procedure is most appropriate when diagnosing a no-crank
condition on a medium/heavy-duty truck equipped with a
conventional electric starter system?
A. Replace the starter motor before testing any circuit
B. Test fuel pressure at the injection system
C. Verify battery state of charge, cable integrity, and voltage available at
the starter circuit
D. Remove the fuel injectors and inspect the spray pattern
Rationale: A no-crank diagnosis should begin with the electrical supply
and starting circuit. Battery condition, cable resistance, connections,
starter control circuits, and available voltage should be verified before
replacing components.
, 2. During a voltage-drop test across a battery cable while the starter is
cranking, an excessive reading most directly indicates what
condition?
A. Excessive alternator output
B. High resistance in the cable or its connections
C. Low engine coolant temperature
D. Excessive fuel pressure
Rationale: Voltage drop measures unwanted resistance under load. An
excessive voltage drop across a starter cable commonly indicates
corrosion, loose connections, damaged conductors, or inadequate cable
capacity.
3. What is the primary purpose of a diesel engine's glow plug or
intake-air heating system during cold starting?
A. Increase engine oil pressure
B. Increase turbocharger boost
C. Promote ignition of the injected fuel by increasing the temperature of
the air or combustion area
D. Reduce alternator loading
Rationale: Diesel combustion depends on compression-generated heat.
Glow plugs or intake heaters provide additional heat during cold
conditions to improve fuel ignition and starting performance.
, 4. A diesel engine cranks at normal speed but does not start. Which
condition should be investigated before condemning the electronic
engine control module?
A. Cab interior lighting
B. Windshield washer pressure
C. Crankshaft position signal and fuel delivery or injection authorization
D. Trailer brake adjustment
Rationale: Engine position information and fuel delivery are
fundamental requirements for diesel operation. A missing crankshaft
signal or lack of injection authorization can prevent starting even when
cranking speed is normal.
5. What is the principal function of the engine oil pump in a
medium/heavy-duty diesel engine?
A. Remove carbon from the exhaust
B. Circulate pressurized lubricating oil to bearings, moving components,
and other lubrication points
C. Regulate fuel injector timing mechanically
D. Increase intake manifold temperature
Rationale: The oil pump supplies lubricating oil throughout the engine.
Adequate oil pressure and flow are essential for protecting bearings,
camshaft components, pistons, and other moving parts.
, 6. Why is maintaining the manufacturer's specified engine oil viscosity
particularly important in a heavy-duty diesel engine?
A. It determines the vehicle's tire pressure
B. It controls the transmission gear ratio
C. It affects lubrication flow, cold-start performance, and protection at
operating temperature
D. It determines the electrical system voltage
Rationale: Oil viscosity affects how readily oil flows during startup and
how well an adequate lubricating film is maintained at operating
temperature. Using an unsuitable viscosity can compromise engine
protection.
7. What is the most likely consequence of operating a diesel engine
with chronically low engine oil pressure?
A. Increased windshield-wiper speed
B. Improved fuel atomization
C. Accelerated wear or catastrophic damage to lubricated engine
components
D. Increased coolant concentration
Rationale: Low oil pressure can prevent critical components from
receiving adequate lubrication. Continued operation can result in
bearing, camshaft, turbocharger, or other severe engine damage.
Technician Assessment Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which procedure is most appropriate when diagnosing a no-crank
condition on a medium/heavy-duty truck equipped with a
conventional electric starter system?
A. Replace the starter motor before testing any circuit
B. Test fuel pressure at the injection system
C. Verify battery state of charge, cable integrity, and voltage available at
the starter circuit
D. Remove the fuel injectors and inspect the spray pattern
Rationale: A no-crank diagnosis should begin with the electrical supply
and starting circuit. Battery condition, cable resistance, connections,
starter control circuits, and available voltage should be verified before
replacing components.
, 2. During a voltage-drop test across a battery cable while the starter is
cranking, an excessive reading most directly indicates what
condition?
A. Excessive alternator output
B. High resistance in the cable or its connections
C. Low engine coolant temperature
D. Excessive fuel pressure
Rationale: Voltage drop measures unwanted resistance under load. An
excessive voltage drop across a starter cable commonly indicates
corrosion, loose connections, damaged conductors, or inadequate cable
capacity.
3. What is the primary purpose of a diesel engine's glow plug or
intake-air heating system during cold starting?
A. Increase engine oil pressure
B. Increase turbocharger boost
C. Promote ignition of the injected fuel by increasing the temperature of
the air or combustion area
D. Reduce alternator loading
Rationale: Diesel combustion depends on compression-generated heat.
Glow plugs or intake heaters provide additional heat during cold
conditions to improve fuel ignition and starting performance.
, 4. A diesel engine cranks at normal speed but does not start. Which
condition should be investigated before condemning the electronic
engine control module?
A. Cab interior lighting
B. Windshield washer pressure
C. Crankshaft position signal and fuel delivery or injection authorization
D. Trailer brake adjustment
Rationale: Engine position information and fuel delivery are
fundamental requirements for diesel operation. A missing crankshaft
signal or lack of injection authorization can prevent starting even when
cranking speed is normal.
5. What is the principal function of the engine oil pump in a
medium/heavy-duty diesel engine?
A. Remove carbon from the exhaust
B. Circulate pressurized lubricating oil to bearings, moving components,
and other lubrication points
C. Regulate fuel injector timing mechanically
D. Increase intake manifold temperature
Rationale: The oil pump supplies lubricating oil throughout the engine.
Adequate oil pressure and flow are essential for protecting bearings,
camshaft components, pistons, and other moving parts.
, 6. Why is maintaining the manufacturer's specified engine oil viscosity
particularly important in a heavy-duty diesel engine?
A. It determines the vehicle's tire pressure
B. It controls the transmission gear ratio
C. It affects lubrication flow, cold-start performance, and protection at
operating temperature
D. It determines the electrical system voltage
Rationale: Oil viscosity affects how readily oil flows during startup and
how well an adequate lubricating film is maintained at operating
temperature. Using an unsuitable viscosity can compromise engine
protection.
7. What is the most likely consequence of operating a diesel engine
with chronically low engine oil pressure?
A. Increased windshield-wiper speed
B. Improved fuel atomization
C. Accelerated wear or catastrophic damage to lubricated engine
components
D. Increased coolant concentration
Rationale: Low oil pressure can prevent critical components from
receiving adequate lubrication. Continued operation can result in
bearing, camshaft, turbocharger, or other severe engine damage.
