ASE A9 Light Vehicle Diesel practice test
The A9 test covers diesel engines in pickups and light trucks: high-pressure common rail fuel systems, turbocharging, cold-start hardware, and the modern aftertreatment stack (DPF, EGR, SCR/DEF). Optional for Master status — valuable for anyone working on diesel pickups.
Technician A says many light-truck diesels require the new fuel filter to be primed (filled or purged per procedure) at replacement to avoid a no-start. Technician B says using the specified filter micron rating matters because common rail systems tolerate very little particulate. Who is correct?
How the A9 test works
50 scored questions
+ ~10 unscored research questions
75 minutes
computer-based, at a test center
$62 per test
plus one $34 registration fee per order
Valid 5 years
then a shorter recertification test
ASE does not publish a fixed passing percentage — scores are scaled. Around 65–70% correct is the commonly cited range; aim above 80% in practice so you walk in with margin. The certificate is issued once ASE verifies your required work experience.
What the A9 test covers
The official task list for A9 Light Vehicle Diesel Engines breaks down into these content areas — the practice bank above draws from all of them:
- General diesel engine diagnosis — hard start, smoke color, compression, noise
- Cylinder head, valve train, and engine block service
- Lubrication and cooling systems
- Air induction and exhaust — turbochargers, charge air coolers, restrictions
- Fuel system — high-pressure common rail, injectors, low-pressure supply, water in fuel
- Emissions and aftertreatment — EGR, DPF regeneration, SCR/DEF
Frequently asked
- How many questions are on the ASE A9 test?
- The A9 test has 50 scored questions plus about 10 unscored research questions, with a 75-minute time limit.
- Is A9 required for Master Automobile Technician status?
- No — Master status requires A1 through A8. A9 is an additional credential for light-vehicle diesel work.
- How does A9 differ from the T2 diesel test?
- A9 targets diesels in cars and light trucks (pickup-class common rail engines); T2 covers medium and heavy truck diesel engines. The fundamentals overlap, but the platforms and systems differ.