ENGINE DIAGNOSTICS AND
MAINTENANCE PROCEDURES 300+
LATEST QUESTIONS WITH
ANSWERS ALREADY VERIFIED BY
EXPERTS 2025 EXAM
What is the first step in engine repair? - CORRECT ANSWER>>>>Correct diagnosis is the first
step in engine repair.
Why is customer information important in diagnosing engine problems? - CORRECT
ANSWER>>>>The customer is often the first link in the diagnostic chain and can provide
valuable information about the complaint.
What should be done after establishing the complaint from the customer? - CORRECT
ANSWER>>>>Verify the information by conducting a thorough road test and comprehensive
diagnosis.
What role do maintenance records play in diagnosing engine issues? - CORRECT
ANSWER>>>>Reviewing maintenance records can reveal if lack of required maintenance is a
cause of mechanical failure.
What is the number one cause of mechanical engine failure? - CORRECT ANSWER>>>>Lack
of required maintenance, such as oil changes.
What preliminary checks should be performed after identifying a complaint? - CORRECT
ANSWER>>>>Check for leaks, listen for abnormal noises, and observe excessive use of oil,
coolant, or fuel.
What tests can help determine the cause of engine issues? - CORRECT ANSWER>>>>Perform
cylinder leakage and balance tests.
What should be the focus during diagnosis and repair? - CORRECT ANSWER>>>>Diagnose
and repair the real problem, not just the symptoms.
What should be checked visually during the diagnosis process? - CORRECT
ANSWER>>>>Check electrical connections, vacuum lines, and wiring to and from the
Powertrain Control Module (ECM).
What is the purpose of Technical Service Bulletins (TSBs)? - CORRECT ANSWER>>>>TSBs
provide information about problems and fixes discovered in the field that may not be in the
manufacturer's service manual.
1
,What caution should be taken when disconnecting electrical connectors? - CORRECT
ANSWER>>>>Never disconnect electrical connectors with the ignition switch ON to avoid
high-voltage spikes.
How should static-sensitive parts be handled? - CORRECT ANSWER>>>>Use a wrist static
strap to drain static charge from your body.
What should be done before welding on a vehicle? - CORRECT ANSWER>>>>Disconnect any
computers to prevent damage from welding.
What can a hand-held scanner or scan tool do? - CORRECT ANSWER>>>>Read stored fault
codes, display electrical signals, override operating parameters, perform automated tests, and
provide bidirectional control of engine actuators.
What should be checked for leaks in the engine? - CORRECT ANSWER>>>>Visual inspection
for fuel, oil, coolant, or other leaks should be performed before, during, and after engine warm-
up.
What indicates a fuel leak in the fuel system? - CORRECT ANSWER>>>>Fuel leaks can come
from damaged lines, hoses, loose fittings, or damaged O-rings.
What are common causes of fuel leaks? - CORRECT ANSWER>>>>Damaged lines or hoses,
loose or damaged fittings, and internal system leaks from fuel injectors or pressure regulators.
What can cause oil leaks? - CORRECT ANSWER>>>>Hardened or worn seals and gaskets,
leaking oil pressure sending units, or an overfilled crankcase.
How can leaking fuel injectors be diagnosed? - CORRECT ANSWER>>>>By changes in fuel
trims displayed by the scan tool or through the use of an exhaust gas analyzer.
What does rapid drop in fuel pressure after turning the key off indicate? - CORRECT
ANSWER>>>>It can indicate an internal system leak.
What should be inspected to find fuel leaks? - CORRECT ANSWER>>>>Inspect hoses for
cracks, swelling, and the condition of hose clamps, as well as fuel lines for cracks and corrosion.
What is the significance of checking fuel tanks and their fittings? - CORRECT
ANSWER>>>>Fuel tanks and fittings are exposed to harsh conditions and can be damaged,
leading to leaks.
What can excessive crankcase pressure cause in an engine? - CORRECT ANSWER>>>>It can
cause engine oil leaks by pushing oil past seals and gaskets.
What are common symptoms of excessive oil consumption in an engine? - CORRECT
ANSWER>>>>Customer complaints of excessive oil consumption, low oil levels, and spark
plugs that are oil-fouled or show signs of oil deposits.
2
,What visual indicators suggest that an engine is burning oil? - CORRECT ANSWER>>>>Blue-
grey or gray-white smoke from the exhaust.
What is the role of the crankcase ventilation system? - CORRECT ANSWER>>>>It needs to
provide fresh air to the crankcase; all components must be unobstructed.
What should be felt at the PCV valve inlet when the engine is idling? - CORRECT
ANSWER>>>>A strong suction.
What happens if engine oil is not changed regularly? - CORRECT ANSWER>>>>The PCV
system can clog.
How can you check for oil leaks in a vehicle? - CORRECT ANSWER>>>>Start the engine, let it
reach normal operating temperature, park over cardboard, and check for dripping fluids.
What colors can engine oil be? - CORRECT ANSWER>>>>Brown, dark brown, or black.
What color and smell are associated with automatic transmission fluid? - CORRECT
ANSWER>>>>Red or dark brown with a distinct smell.
What colors can antifreeze be? - CORRECT ANSWER>>>>Green, orange, or red.
What color can power steering fluid be? - CORRECT ANSWER>>>>Red or clear.
What color can brake fluid be? - CORRECT ANSWER>>>>Clear or dark brown.
What should be checked for leaks in the cooling system? - CORRECT ANSWER>>>>Hoses,
water pump, radiator, intake manifold, sensor fittings, lines, water control valves, coolers, air
compressor, and heater core.
How can you test for leaks in the cooling system? - CORRECT ANSWER>>>>Attach a
pressure tester to the coolant filler neck and apply pressure equal to the radiator cap's rating.
What indicates an internal coolant leak when inspecting engine oil? - CORRECT
ANSWER>>>>Excessive oil level or milky color in the oil.
What are potential causes of a pressure drop in the cooling system without external leaks? -
CORRECT ANSWER>>>>Defective intake manifold or timing cover gasket, blown head
gasket, cracked cylinder head, or cracked engine block.
What symptoms may occur if coolant leaks into a cylinder? - CORRECT ANSWER>>>>White
exhaust smoke and a sweet coolant odor in the exhaust.
What can misfiring in an engine indicate when combined with coolant leaks? - CORRECT
ANSWER>>>>It may indicate an internal coolant leak, especially when the engine is cold.
3
, What is a method to locate hard-to-find oil leaks? - CORRECT ANSWER>>>>Add a
fluorescent dye to the engine oil and use a black light to check for leaks.
What should be done if the source of an oil leak is not obvious? - CORRECT
ANSWER>>>>Thoroughly clean the engine and surrounding components, then check for leaks
again.
What is the main job of brake fluid? - CORRECT ANSWER>>>>To exert pressure.
What should you do if the pressure drops during a cooling system test? - CORRECT
ANSWER>>>>Check for leaks at the previously discussed areas.
What is the significance of the color and texture of various fluids when diagnosing leaks? -
CORRECT ANSWER>>>>Familiarity with the color, texture, and smell helps identify the type
of fluid leaking.
What does a properly functioning PCV system prevent? - CORRECT ANSWER>>>>Excessive
crankcase pressure.
What can cause misfiring in an engine, especially when cold? - CORRECT
ANSWER>>>>Misfiring can occur due to small coolant leaks that are masked by catalytic
converters.
How can coolant leaks affect oxygen sensors? - CORRECT ANSWER>>>>Coolant can damage
sensitive oxygen sensors.
What indicates that combustion gases are escaping into the cooling system? - CORRECT
ANSWER>>>>Air bubbles appearing in the radiator coolant.
What happens to the recovery reservoir when combustion gases are present? - CORRECT
ANSWER>>>>The recovery reservoir can become pressurized when the engine is running.
What is one method for detecting combustion gases in the cooling system? - CORRECT
ANSWER>>>>Using a chemical sensitive to combustion gases placed over the radiator neck; a
color change indicates the presence of combustion gases.
How can an exhaust analyzer probe be used to detect combustion gases? - CORRECT
ANSWER>>>>By carefully holding the probe over the neck of the radiator; a reading on the
analyzer indicates combustion gases.
What can be done to identify a leaking cylinder? - CORRECT ANSWER>>>>Disabling each
cylinder can help find the leaking one, as bubbles in the radiator will diminish when the leaking
cylinder is disabled.
4
MAINTENANCE PROCEDURES 300+
LATEST QUESTIONS WITH
ANSWERS ALREADY VERIFIED BY
EXPERTS 2025 EXAM
What is the first step in engine repair? - CORRECT ANSWER>>>>Correct diagnosis is the first
step in engine repair.
Why is customer information important in diagnosing engine problems? - CORRECT
ANSWER>>>>The customer is often the first link in the diagnostic chain and can provide
valuable information about the complaint.
What should be done after establishing the complaint from the customer? - CORRECT
ANSWER>>>>Verify the information by conducting a thorough road test and comprehensive
diagnosis.
What role do maintenance records play in diagnosing engine issues? - CORRECT
ANSWER>>>>Reviewing maintenance records can reveal if lack of required maintenance is a
cause of mechanical failure.
What is the number one cause of mechanical engine failure? - CORRECT ANSWER>>>>Lack
of required maintenance, such as oil changes.
What preliminary checks should be performed after identifying a complaint? - CORRECT
ANSWER>>>>Check for leaks, listen for abnormal noises, and observe excessive use of oil,
coolant, or fuel.
What tests can help determine the cause of engine issues? - CORRECT ANSWER>>>>Perform
cylinder leakage and balance tests.
What should be the focus during diagnosis and repair? - CORRECT ANSWER>>>>Diagnose
and repair the real problem, not just the symptoms.
What should be checked visually during the diagnosis process? - CORRECT
ANSWER>>>>Check electrical connections, vacuum lines, and wiring to and from the
Powertrain Control Module (ECM).
What is the purpose of Technical Service Bulletins (TSBs)? - CORRECT ANSWER>>>>TSBs
provide information about problems and fixes discovered in the field that may not be in the
manufacturer's service manual.
1
,What caution should be taken when disconnecting electrical connectors? - CORRECT
ANSWER>>>>Never disconnect electrical connectors with the ignition switch ON to avoid
high-voltage spikes.
How should static-sensitive parts be handled? - CORRECT ANSWER>>>>Use a wrist static
strap to drain static charge from your body.
What should be done before welding on a vehicle? - CORRECT ANSWER>>>>Disconnect any
computers to prevent damage from welding.
What can a hand-held scanner or scan tool do? - CORRECT ANSWER>>>>Read stored fault
codes, display electrical signals, override operating parameters, perform automated tests, and
provide bidirectional control of engine actuators.
What should be checked for leaks in the engine? - CORRECT ANSWER>>>>Visual inspection
for fuel, oil, coolant, or other leaks should be performed before, during, and after engine warm-
up.
What indicates a fuel leak in the fuel system? - CORRECT ANSWER>>>>Fuel leaks can come
from damaged lines, hoses, loose fittings, or damaged O-rings.
What are common causes of fuel leaks? - CORRECT ANSWER>>>>Damaged lines or hoses,
loose or damaged fittings, and internal system leaks from fuel injectors or pressure regulators.
What can cause oil leaks? - CORRECT ANSWER>>>>Hardened or worn seals and gaskets,
leaking oil pressure sending units, or an overfilled crankcase.
How can leaking fuel injectors be diagnosed? - CORRECT ANSWER>>>>By changes in fuel
trims displayed by the scan tool or through the use of an exhaust gas analyzer.
What does rapid drop in fuel pressure after turning the key off indicate? - CORRECT
ANSWER>>>>It can indicate an internal system leak.
What should be inspected to find fuel leaks? - CORRECT ANSWER>>>>Inspect hoses for
cracks, swelling, and the condition of hose clamps, as well as fuel lines for cracks and corrosion.
What is the significance of checking fuel tanks and their fittings? - CORRECT
ANSWER>>>>Fuel tanks and fittings are exposed to harsh conditions and can be damaged,
leading to leaks.
What can excessive crankcase pressure cause in an engine? - CORRECT ANSWER>>>>It can
cause engine oil leaks by pushing oil past seals and gaskets.
What are common symptoms of excessive oil consumption in an engine? - CORRECT
ANSWER>>>>Customer complaints of excessive oil consumption, low oil levels, and spark
plugs that are oil-fouled or show signs of oil deposits.
2
,What visual indicators suggest that an engine is burning oil? - CORRECT ANSWER>>>>Blue-
grey or gray-white smoke from the exhaust.
What is the role of the crankcase ventilation system? - CORRECT ANSWER>>>>It needs to
provide fresh air to the crankcase; all components must be unobstructed.
What should be felt at the PCV valve inlet when the engine is idling? - CORRECT
ANSWER>>>>A strong suction.
What happens if engine oil is not changed regularly? - CORRECT ANSWER>>>>The PCV
system can clog.
How can you check for oil leaks in a vehicle? - CORRECT ANSWER>>>>Start the engine, let it
reach normal operating temperature, park over cardboard, and check for dripping fluids.
What colors can engine oil be? - CORRECT ANSWER>>>>Brown, dark brown, or black.
What color and smell are associated with automatic transmission fluid? - CORRECT
ANSWER>>>>Red or dark brown with a distinct smell.
What colors can antifreeze be? - CORRECT ANSWER>>>>Green, orange, or red.
What color can power steering fluid be? - CORRECT ANSWER>>>>Red or clear.
What color can brake fluid be? - CORRECT ANSWER>>>>Clear or dark brown.
What should be checked for leaks in the cooling system? - CORRECT ANSWER>>>>Hoses,
water pump, radiator, intake manifold, sensor fittings, lines, water control valves, coolers, air
compressor, and heater core.
How can you test for leaks in the cooling system? - CORRECT ANSWER>>>>Attach a
pressure tester to the coolant filler neck and apply pressure equal to the radiator cap's rating.
What indicates an internal coolant leak when inspecting engine oil? - CORRECT
ANSWER>>>>Excessive oil level or milky color in the oil.
What are potential causes of a pressure drop in the cooling system without external leaks? -
CORRECT ANSWER>>>>Defective intake manifold or timing cover gasket, blown head
gasket, cracked cylinder head, or cracked engine block.
What symptoms may occur if coolant leaks into a cylinder? - CORRECT ANSWER>>>>White
exhaust smoke and a sweet coolant odor in the exhaust.
What can misfiring in an engine indicate when combined with coolant leaks? - CORRECT
ANSWER>>>>It may indicate an internal coolant leak, especially when the engine is cold.
3
, What is a method to locate hard-to-find oil leaks? - CORRECT ANSWER>>>>Add a
fluorescent dye to the engine oil and use a black light to check for leaks.
What should be done if the source of an oil leak is not obvious? - CORRECT
ANSWER>>>>Thoroughly clean the engine and surrounding components, then check for leaks
again.
What is the main job of brake fluid? - CORRECT ANSWER>>>>To exert pressure.
What should you do if the pressure drops during a cooling system test? - CORRECT
ANSWER>>>>Check for leaks at the previously discussed areas.
What is the significance of the color and texture of various fluids when diagnosing leaks? -
CORRECT ANSWER>>>>Familiarity with the color, texture, and smell helps identify the type
of fluid leaking.
What does a properly functioning PCV system prevent? - CORRECT ANSWER>>>>Excessive
crankcase pressure.
What can cause misfiring in an engine, especially when cold? - CORRECT
ANSWER>>>>Misfiring can occur due to small coolant leaks that are masked by catalytic
converters.
How can coolant leaks affect oxygen sensors? - CORRECT ANSWER>>>>Coolant can damage
sensitive oxygen sensors.
What indicates that combustion gases are escaping into the cooling system? - CORRECT
ANSWER>>>>Air bubbles appearing in the radiator coolant.
What happens to the recovery reservoir when combustion gases are present? - CORRECT
ANSWER>>>>The recovery reservoir can become pressurized when the engine is running.
What is one method for detecting combustion gases in the cooling system? - CORRECT
ANSWER>>>>Using a chemical sensitive to combustion gases placed over the radiator neck; a
color change indicates the presence of combustion gases.
How can an exhaust analyzer probe be used to detect combustion gases? - CORRECT
ANSWER>>>>By carefully holding the probe over the neck of the radiator; a reading on the
analyzer indicates combustion gases.
What can be done to identify a leaking cylinder? - CORRECT ANSWER>>>>Disabling each
cylinder can help find the leaking one, as bubbles in the radiator will diminish when the leaking
cylinder is disabled.
4
