The A1 is all about the engine itself: diagnosing noises and leaks, testing compression, cylinder heads and valve train, the block and rotating assembly, plus lubrication and cooling.
A lot of A1 questions are about figuring out what a test result actually means. Read each one slowly and think about what the numbers are telling you before you pick.
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Question 1 of 15
Technician A says an oil of the correct viscosity meets the requirement even without the specified rating or approval. Technician B says oil life monitors count down by mileage, like a fixed service interval. Who is correct?
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Answer: D. Neither A nor B
Viscosity is only part of the specification; the rating or approval covers the additive package the engine needs. Technician A is wrong. Most oil life monitors estimate oil life from how the engine is used (revolutions, temperatures, short trips), not from distance alone. Technician B is wrong too.
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Question 2 of 15
A relative compression test shows every current peak the same height. Technician A says this confirms every cylinder has adequate compression. Technician B says the test only compares cylinders with each other, so a cranking compression test is still needed to measure the actual pressure. Who is correct?
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Answer: B. B only
A relative compression test compares the starter current peaks with each other, so it finds a cylinder that is weaker than the rest. If every cylinder is equally low, from engine-wide wear or late valve timing, the peaks still match. Even peaks don't prove adequate compression, so Technician A is wrong. A gauge test measures the actual pressure in each cylinder, so Technician B is right.
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Question 3 of 15
A fuel pump has been replaced for low fuel pressure. How should the repair be verified?
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Answer: A. Measure fuel pressure and volume against spec
A pump must deliver both pressure and volume. Measuring both against specification confirms the new pump, and that nothing else such as a filter, regulator or wiring is limiting it. A pump can make pressure with no flow and still starve the engine under load.
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Question 4 of 15
All of these can cause excessive oil consumption **EXCEPT**:
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Answer: A. A restricted fuel filter
Oil is consumed when it is burned in the combustion chamber or leaks out. Worn guides and rings let oil into the cylinders, and a restricted PCV system raises crankcase pressure, forcing oil past seals and gaskets. A restricted fuel filter affects fuel delivery only and has no path to consume oil.
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Question 5 of 15
A new rear main seal leaks within weeks. With it removed, the crankshaft's seal surface has a smooth groove worn where the old seal's lip rode. An approved repair sleeve is available for this crankshaft. What is the correct repair?
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Answer: B. Fit the repair sleeve, then a new seal
A lip seal can only seal against a smooth, round surface, and a new seal riding in an old groove leaks. Pressing the repair sleeve over the worn area restores a smooth sealing surface, and the new seal is installed square with the proper tool. Where service information allows, seating the seal at a depth that puts its lip on unworn metal is the alternative.
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Question 6 of 15
When installing positive-type valve stem seals, all of these are correct **EXCEPT**:
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Answer: B. Sliding the seal over the stem without covering the lock grooves
The sharp lock grooves can cut a seal's lip as it slides over them, so a protective sleeve goes over the stem tip first. Sliding a seal on without that protection is the incorrect step. Fitting the sleeve, seating the seal fully with the proper tool and lubricating it as directed are all correct.
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Question 7 of 15
Technician A says a small, steady drip from the weep hole is normal for a water pump in service. Technician B says a pump with a loose or eroded impeller can cause overheating without leaking. Who is correct?
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Answer: B. B only
A little seepage while a new seal beds in may be normal, but a steady drip from the weep hole means the seal is failing and the pump is replaced. Technician A is wrong. An impeller that has eroded or slipped on its shaft turns without moving enough coolant, causing overheating with no visible leak. Technician B is right.
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Question 8 of 15
A vacuum gauge shows a regular drop that points to a valve in one cylinder not sealing. Which test best identifies both the cylinder and whether the intake or exhaust valve is leaking?
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Answer: A. A cylinder leak-down test, listening at the intake and exhaust
A compression test can find the weak cylinder, but only a leak-down test shows which way the air escapes. Air heard at the throttle body means the intake valve is leaking, and air at the tailpipe means the exhaust valve.
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Question 9 of 15
Technician A says an over-oiled aftermarket air filter only adds airflow restriction and doesn't affect sensor readings. Technician B says a leak at one intake runner's gasket would lean out all cylinders equally. Who is correct?
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Answer: D. Neither A nor B
Excess oil from a re-oiled filter can be drawn onto the mass airflow sensor element, making it under-read airflow, so Technician A is wrong. A gasket leak at a single runner admits unmetered air mainly to that cylinder, leaning it until it misfires while the others run normally, so Technician B is wrong too.
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Question 10 of 15
Technician A says a DMM set to DC volts can measure voltage drop in the starter circuit while the engine is cranking. Technician B says a DMM's min/max recording function can catch a brief voltage dropout that the live display would miss, as long as the dropout isn't faster than the meter can respond. Who is correct?
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Answer: C. Both A and B
Voltage drop is measured across part of a circuit while current is flowing, so cranking is exactly when to measure starter circuit drop. Technician A is right. Min/max recording captures the lowest and highest readings over time, including dropouts too quick for the live display, within the meter's response speed, so Technician B is right too. Very fast events still need a scope.
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Question 11 of 15
After a rebuild, a four-cylinder engine has a strong vibration that rises with engine speed. All cylinders contribute equally on a power balance test, the mounts are good, and the vibration wasn't present before. The engine has a chain-driven balance shaft. What is the most likely cause?
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Answer: B. The balance shaft was installed out of time
A balance shaft cancels the engine's natural shaking force, but only when it's timed correctly to the crankshaft. Installed a tooth or more out, it adds vibration instead of canceling it, and the shaking rises with rpm. The shaft must be retimed to the marks.
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Question 12 of 15
An engine rattles at the front for two or three seconds after a cold start, then goes quiet once oil pressure builds. Cam-to-crank correlation is within specification. What is the most likely cause?
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Answer: B. A hydraulic tensioner bleeding down while parked
A hydraulic tensioner relies on oil pressure to hold the chain tight. If it bleeds down while the engine sits, the chain is slack at start-up and rattles until oil pressure refills the tensioner. The location at the front and the way the noise clears as pressure arrives both point to the tensioner, and correlation within spec makes significant chain stretch unlikely.
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Question 13 of 15
A rear main seal leaks mostly on highway trips. A card held at the oil filler at idle is pushed away, showing crankcase pressure. What should the technician check before replacing the seal?
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Answer: D. The PCV system for a restriction
The crankcase should be at a slight vacuum. Positive pressure, worst under highway load when blow-by is highest, forces oil past seals. A restricted PCV system is the usual cause, and a new seal will leak again unless it's fixed.
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Question 14 of 15
Which setup is correct for a cranking compression test?
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Answer: C. Warm engine, all plugs out, throttle wide open, fuel and spark off
A warm engine reads consistently. Removing all plugs lets the engine crank fast and evenly, and a wide-open throttle lets each cylinder fill fully. Fuel is disabled so no fuel is sprayed in, and ignition is disabled for safety and to protect the coils. Each cylinder is cranked through the same number of compression strokes.
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Question 15 of 15
A fuel line on a port fuel-injected engine must be disconnected to replace a fuel filter. What should be done first?
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Answer: D. Relieve fuel system pressure following the procedure
Fuel injection systems hold pressure after the engine stops. Pressure is relieved first, often by disabling the pump and running the engine until it stalls, or with a gauge bleed, so opening the line doesn't spray fuel. Eye protection and a fire extinguisher are kept nearby.
Want more? ASE Pro has 2,100+ practice questions with explanations.
Missed the diagnosis questions? Practice reading compression and leak-down results until you can tell a valve problem from a ring problem without thinking about it.
Measurement questions are easy points once you know your specs and tools. Don't skip them.
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ASE Pro has 2,100+ practice questions with explanations, timed practice exams, and weak-area drills.