The ASE A9 Light Vehicle Diesel Engines test has 50 scored questions plus 10 unscored research questions, and you get 75 minutes to finish it. Our free ASE A9 practice tests use the same multiple-choice style and cover each content area on the exam, so you can find weak spots before you pay the $62 test fee and the $34 registration fee.
A9 covers diesel engines in light-duty pickups, vans and SUVs: diagnosis, cylinder heads and valve trains, engine blocks, lubrication and cooling, air induction and exhaust aftertreatment, and fuel systems. Below you will find how the exam works, a step-by-step study plan, what to expect on test day, and how to get the most out of each practice quiz.
A9 is the ASE certification test for technicians who diagnose and repair diesel engines in light vehicles. It belongs to the A1-A9 automobile and light truck series and checks whether you can work through diesel problems in a logical order instead of swapping parts until the symptom goes away.
The people who usually take it:
Passing the test is only part of certification. ASE also requires relevant hands-on work experience. If you pass before that experience is approved, ASE holds your certificate until it is. A9 certification is valid for five years. After that, you keep it current with the shorter A9R recertification test or through the ASE Renewal App.
Practice Test Geeks is an independent study site. We are not affiliated with ASE (National Institute for Automotive Service Excellence). For official requirements and to register, use the ASE website.
Facts verified Nov 11, 2026 against ASE. Dates that have passed are removed automatically.
| Item | Detail | Official source |
|---|---|---|
| Number of questions (Initial certification) | 50 scored questions | ASE |
| Number of questions (Recertification (A9R)) | 25 scored questions | ASE |
| Time limit (Initial certification) | 75 minutes | ASE |
| Time limit (Recertification (A9R)) | 30 minutes | ASE |
| Exam fee (ASE Renewal App) | $52 per year | ASE |
| Exam fee (Certification test) | $62 per test + $34 registration fee per order | ASE |
| Exam fee (Registration fee) | $34 per order | ASE |
| Retake policy | Wait 30 full days | ASE |
| Validity | 5 years | ASE |
| Renewal | Recertification test or ASE Renewal App | ASE |
| Delivery | Prometric test center; online remote proctoring for recertification | ASE |
| Eligibility | Passing test plus hands-on work experience | ASE |
| Eligibility (Recertification) | Previously passed A9 | ASE |
| Score release | Within 24 hours in myASE | ASE |
| Registration deadline | 90 days from purchase to test | ASE |
| Testing window (Fall 2026) | Oct 10 – Dec 31, 2026 | ASE |
Facts verified Nov 11, 2026 against ASE. Dates that have passed are removed automatically.
Prepare for the Light Vehicle Diesel Engines (Test A9) exam with our free practice test modules. Each quiz covers key topics to help you pass on your first try.
Each practice quiz below matches one content area of the Light Vehicle Diesel Engines (Test A9). Start with the area you know least.
This area covers the diagnostic approach behind every other part of A9. You need to check and confirm the customer's complaint, review service history and use a scan tool to read diagnostic trouble codes, freeze-frame data and live sensor values. Study what diesel exhaust smoke tells you: black usually means too much fuel or too little air, white points to unburned fuel or coolant, and blue means the engine is burning oil. Know when to use a compression test, a cylinder contribution or balance test, a crankcase blow-by check or an oil analysis. Practice reading strange noises, vibrations and no-start or hard-start complaints, and choosing the test that narrows the cause before any parts get replaced.
This area covers inspecting and repairing cylinder heads and their components. Study how to check a head for cracks, warpage and flatness, how to inspect valves, seats, guides and springs, and how to measure and adjust valve lash. Know overhead camshaft and pushrod layouts, rocker arms, hydraulic and mechanical lifters, and how to time the camshaft correctly. Diesel-specific items include injector sleeves or bores, where a leak can let coolant or combustion gases into places they don't belong, and head gasket failures that pressurize the cooling system. Learn the proper torque procedures, torque-to-yield head bolts and when parts have to be replaced rather than reused.
This area covers the bottom end. Study how to measure cylinder bores and liners for taper and out-of-round, how to inspect pistons, rings and wrist pins, and how to check connecting rods. Know how to inspect a crankshaft, measure main and rod bearing clearance, check crankshaft end play and recognize bearing wear patterns that point to lubrication or alignment problems. Review vibration dampers, flywheels, gear trains and timing drives, along with rear and front main seals. Expect questions that link a symptom, such as a knock, low oil pressure or too much blow-by, to the measurement that confirms a specific internal fault.
This area covers keeping a diesel engine at the right temperature and properly oiled. On the lubrication side, study oil pumps, pressure regulation, filters, oil coolers and piston cooling jets, and know how to diagnose low or high oil pressure and oil contamination by fuel or coolant. On the cooling side, review thermostats, water pumps, fan clutches and electronic fans, radiators, pressure caps and coolant condition. Know how to pressure-test the system, check coolant with a refractometer or test strips, and trace where coolant is going. Understand how a failed oil cooler or EGR cooler can mix fluids or cause overheating, and which tests isolate each one.
This area covers air going into the engine and exhaust coming out of it. Study air filters and restriction indicators, intake and boost leaks, charge air coolers, and turbochargers, including wastegate and variable-geometry designs and the symptoms of a failing turbo. On the exhaust side, review exhaust gas recirculation (EGR) valves and coolers, the diesel oxidation catalyst, the diesel particulate filter and how it regenerates, and selective catalytic reduction with diesel exhaust fluid. Know how sensor readings such as boost, mass airflow and differential pressure point to specific faults. Expect questions on low power, excessive smoke and emissions-related warning lights.
This area covers the diesel fuel system from the tank to the injector. Study lift pumps and low-pressure supply, fuel filters and water separators, and how air or water in the fuel causes hard starting and rough running. Know how high-pressure common-rail systems work: the high-pressure pump, the rail, pressure sensors and regulators, and electronically controlled injectors. Review injector return-flow testing, balance rate data and the safety precautions for working on high-pressure lines. Include cold-start aids such as glow plugs and intake heaters, and learn how to tell a fuel-delivery fault from an air or compression fault when a diesel cranks but won't start.
The initial A9 certification test has 50 scored questions and 10 unscored research questions, with 75 minutes to answer all of them. The research questions look like every other question and aren't marked, so give each question your full effort. Most questions describe a symptom, a test result or a technician's statement and ask for the most likely cause or the right next step. Expect plenty of "Technician A says… Technician B says…" questions, where you decide whether one, both or neither technician is right.
Key logistics:
Because of the 90-day rule, wait until you're nearly ready before you buy the test.
A9 rewards technicians who follow a diagnostic sequence. Use this plan to build that habit:
Your day-to-day diesel work is your best study material. When a truck comes in, talk yourself through the diagnostic steps before you pick up a tool.
Before you go: Check your Prometric appointment confirmation for the address, arrival instructions and ID requirements, and plan to arrive early. Get a normal night's sleep. Last-minute cramming does little for a reasoning test like this one.
During the test:
After the test: ASE emails a detailed score report after your appointment, and results usually show up in myASE within 24 hours. The report breaks down how you did by content area, so use it to guide your next steps.
If you don't pass: You must wait 30 full days before you can buy and schedule A9 again. Use that time to retake the practice quizzes in the areas your score report flagged.
If you pass: Make sure ASE has approved your work experience so your certificate is issued. Plan to renew within five years with A9R or the ASE Renewal App, which costs $52 a year.
Each practice quiz on this page matches one A9 content area, so you can tell exactly where you're losing points. Here's how to get the most out of them:
Practice questions are a study aid, not a copy of the real exam. ASE doesn't release its live questions, and ours are written independently to match the style and subject matter of the content areas. If you can explain the reasoning behind each answer, you are learning the material. If you only recognize questions you've seen before, keep studying.