General Engine Diagnosis
40%of exam
Customer concernVacuum testsCompression testsLeak-downPCVScan tool
Head + Valve Train
13%of exam
Head inspectionValve guidesValve lashCam driveVVT + VVL
Engine Block Repair
9%of exam
Cylinder wallsCrankshaftBearingsPistonsBalance shafts
Lubrication + Cooling
18%of exam
Oil pressureOil pumpsPressure testsThermostatsCooling fans
Related Systems
20%of exam
FuelAir inductionElectricalIgnitionExhaust
Quick Facts
- Exam
- ASE A1
- Focus
- Engine Repair
- Questions
- 55 total / 45 scored
- Time
- 75 minutes
- Domains
- Five content areas
- Largest domain
- General diagnosis: 40%
- Recertification
- A1R: 23 questions / 30 min
- Blueprint
- 2026 study guide
Verify Before Replacing
Verify, research, test, then repair
ConcernInformationTestsRepair
Compression vs Leak-Down
Compression
- Cranking or running test
- Checks cylinder pressure
Leak-down
- Sealing-loss test
- Air path locates loss
Use both for engine condition.
Starting Condition Path
- No crank→Decide mechanical or subsystem
- Cranks, no start→Separate mechanical or subsystem
- Hard start→Compare operating conditions
- Low compression→Compression, then leak-down
- Compression normal→Test related systems
- Concern unclear→Road-test; research history and TSBs
Diagnosis Starting Points
- Customer concern
- Verify or road-test first
- Service information
- History, TSBs, precautions
- No-crank
- Mechanical or subsystem?
- Crank/no-start
- Mechanical or subsystem?
- Fluid leaks
- Fuel, oil, coolant: locate
- Noise or vibration
- Isolate source before repair
- Consumption + exhaust
- Oil/coolant; color and odor
- Diagnostic tools
- Scope, DMM, scan tool
Compression Needs Company
Cranking, relative, running, leak-down
CrankingRelativeRunningLeak-down
Cranking vs Relative
Cranking compression
- Mechanical pressure test
- Cylinder-specific reading
Relative compression
- Compares cylinders
- Look for imbalance
Choose the needed comparison.
Engine Condition Tests
- Manifold vacuum
- Interpret vacuum or pressure
- Cylinder balance
- Compare power contribution
- Cranking compression
- Interpret cylinder pressure
- Relative compression
- Compare cylinders
- Running compression
- Interpret breathing condition
- Leak-down
- Air path locates seal loss
- PCV
- Test components; interpret results
No-Crank vs No-Start
No-crank
- Engine does not crank
- Separate system condition
Crank/no-start
- Engine cranks
- Isolate mechanical or subsystem
Classify condition before testing.
VVT vs VVL
VVT
- Variable valve timing
- Cam timing concern
VVL
- Variable valve lift
- Valve lift concern
Identify the controlled function.
Cylinder Head Inspection
- Cylinder head
- Remove, clean, prepare
- Cracks and warpage
- Check corrosion and passages
- Valves and seats
- Inspect sealing surfaces
- Spring squareness
- Compare spring height
- Retainers and locks
- Inspect locks and grooves
- Stem seals
- Control oil entry
- Guide clearance
- Support valve stem
Valve Train + Timing
- Lash or preload
- Inspect and adjust
- Lifters and adjusters
- Hydraulic or mechanical
- Cam drive
- Gears, chain, tensioner, belt
- Cam lobes and bore
- Inspect lift and alignment
- Cam timing
- Time cam to crank
- Head finish + bolts
- OEM gasket and torque
- VVT and VVL
- Inspect controlled components
Repair Scope Path
- Head removed→Inspect finish; use OEM torque
- Valve train concern→Check lash, lifters, cam
- Block disassembly→Mark orientation; inspect parts
- Engine assembly→Specified sealers; prime lube
- Related fault→Test fuel, air, electrical, ignition, exhaust
Block + Bottom End
- Cylinder walls
- Clean and inspect bore
- Crankshaft
- End play, journals, keyway
- Tone wheel
- Inspect where equipped
- Main bearings
- Wear, bore, cap location
- Bearing clearance
- Check clearance and alignment
- Connecting rods
- Damage, bore, cap marks
- Harmonic balancer
- Control crank vibration
Block Assembly Details
- Engine assembly
- Reinstall; prime lubrication
- Part orientation
- Mark before removal
- Core and gallery plugs
- Seal passages
- Piston oil jets
- Damage, aim, restriction
- Cam bearings
- Wear, damage, alignment
- Balance shafts
- Time shaft to crank
- Piston/bearing patterns
- Identify wear pattern
- Flywheel or flexplate
- Cracks, wear, runout
- Pans and covers
- Inspect and replace
- Gaskets and sealers
- Use specified materials
- In-block VVT
- Inspect controlled components
- Cylinder deactivation
- Inspect system operation
Pressure Needs Data
Test pressure, pump, relief, cooler
PressurePumpReliefCooler
Oil Pressure vs Leak
Oil pressure
- Lubrication delivery
- Gauge-test system
Oil leak
- External fluid loss
- Perform leak test
Do not merge separate complaints.
Fluid + Temperature Path
- Oil loss→Separate leaks, PCV, consumption
- Coolant loss→Pressure test; note exhaust clues
- Oil pressure concern→Gauge-test pump, relief, drive
- Overheating→Test leaks, flow, airflow
- Condition-related noise→Isolate noise source
Lubrication System
- Oil pressure
- Diagnose and gauge-test
- Oil leaks
- Perform leak test
- Oil pump
- Gears, rotors, pickup, drive
- Relief device
- Inspect control system
- Oil cooler
- Flush, inspect, test
- Oil specification
- Type, viscosity, rating
Cooling Starts Contained
Pressure test, leaks, cap, coolant
PressureLeaksCapCoolant
Cooling System
- Pressure test
- Find cooling-system leaks
- Radiator and heater
- Inspect and test
- Cap and recovery
- Inspect and test
- Hoses, pipes, valves
- Inspect and replace
- Thermostat and bypass
- Verify coolant control
- Water pump
- Mechanical or electric
- Coolant
- Test, flush, fill, bleed
- Fans and shrouds
- Airflow and circuits
- Belts and tensioners
- Inspect alignment and adjust
Common Traps
No-Crank vs Crank/No-Start
Separate conditions ≠ Check related systems
Compression vs Leak-Down
Pressure test differs ≠ Sealing-loss test differs
Oil Leak vs Pressure
Perform leak test ≠ Gauge-test lubrication
VVT vs VVL
Timing control differs ≠ Lift control differs
Inspection vs Replacement
Verify fault first ≠ Use history and TSBs
Last Minute
- 1.Verify concern; road-test first
- 2.Research history, TSBs, precautions
- 3.Classify no-crank, no-start, hard start
- 4.Interpret vacuum, balance, compression, leak-down
- 5.Link consumption to exhaust clues
- 6.Test PCV, scope, DMM, scan tool
- 7.Inspect timing, valve train, head finish
- 8.Check block VVT and deactivation
- 9.Gauge-test oil; leak-test cooling
- 10.Check coolant flow, airflow, belt drive
- 11.Test fuel, air, electrical, ignition, exhaust
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