- A6 Exam Overview: Five Domains, One Test
- Domain 1: General Electrical/Electronic System Diagnosis (26%)
- Domain 2: Battery and Starting System Diagnosis and Repair (18%)
- Domain 3: Charging System Diagnosis and Repair (10%)
- Domain 4: Lighting Systems Diagnosis and Repair (12%)
- Domain 5: Body Electrical Systems Diagnosis and Repair (34%)
- How the Domains Show Up in Question Format
- Mapping a Study Schedule to Domain Weight
- Frequently Asked Questions
- A6 has five domains; Body Electrical Systems alone accounts for 34% (17 of 50 scored questions).
- General Electrical/Electronic System Diagnosis (26%) is the circuit-theory foundation behind every other domain.
- The exam is 60 questions (50 scored, 10 unscored) in 90 minutes - the longest sitting in the Automobile series.
- Questions use direct multiple choice, Technician A/B, and EXCEPT formats built around schematics and multimeter readings.
A6 Exam Overview: Five Domains, One Test
The Automobile & Light Truck Certification - A6 Electrical/Electronic Systems test, administered by ASE, is built from five content areas that add up to 50 scored questions out of the 60 you'll actually answer (the remaining 10 are unscored research items you can't identify during the test). Understanding how these five domains are weighted isn't just trivia - it tells you exactly where to spend your limited study hours before test day.
This guide breaks down each domain in the order ASE lists them, with the percentage of scored questions each one carries so you can prioritize accordingly. If you haven't yet reviewed the mechanics of registration, fees, and scheduling, our A6 Study Guide 2026 walks through the full preparation process, and the A6 Requirements 2026 page covers the work-experience and training prerequisites you'll need before your certificate is issued.
Domain 1: General Electrical/Electronic System Diagnosis (26%)
This domain is the circuit-theory backbone of the entire A6 exam, and its influence extends into every other domain because you can't diagnose a lighting circuit, a starting problem, or a body control module fault without these fundamentals. Expect roughly a quarter of your scored questions to test:
General Electrical/Electronic System Diagnosis
Candidates must be comfortable reading circuits cold, interpreting live data, and tracing faults without guessing.
- Voltage, voltage drop, current, and wattage calculations
- Continuity and resistance testing with a digital multimeter
- Waveform interpretation (oscilloscope patterns)
- Scan tool data streams and bidirectional controls
- Diagnosing shorts, grounds, and opens
- Parasitic draw measurement procedures
- Fusible links and current-limiting devices
- Schematic and wiring diagram reading
- Data bus network failures (CAN, LIN, and similar architectures)
- Module replacement and reprogramming procedures
Because this domain underpins the rest of the exam, it's the domain most worth mastering first. If you're unsure how deep the schematic-reading questions go, our How Hard Is the A6 Exam? guide breaks down the difficulty curve in more detail.
Domain 2: Battery and Starting System Diagnosis and Repair (18%)
Battery and starting system questions make up about 18% of the scored content - nearly one in five questions. This domain tends to reward technicians with real bay-floor experience diagnosing no-start and slow-crank complaints, since the concepts translate directly from shop work to test questions.
Battery and Starting Systems
Focus on battery testing methodology and starter circuit diagnosis under load.
- Battery capacity, conductance, and load testing
- Battery inspection, service, and replacement (including AGM and other chemistries)
- Starter circuit voltage drop testing
- Cranking circuit component diagnosis (solenoids, relays, starter motors)
- Start/stop system interactions with the battery and starting circuit
Technician A/B style questions frequently appear here, presenting two diagnostic approaches to a slow-crank complaint and asking which technician (or both, or neither) is correct.
Domain 3: Charging System Diagnosis and Repair (10%)
Charging system questions represent the smallest domain on the A6 exam at 10% of scored content, but don't mistake "smallest" for "skip." Alternator and charging circuit diagnosis questions are often built around voltage readings at idle versus under load, and they connect conceptually to the general electrical diagnosis domain above.
Charging Systems
Expect questions on output testing and fault isolation within the charging circuit.
- Charging system output and voltage regulation testing
- Alternator diagnosis (noise, output, ripple voltage)
- Charging circuit wiring and connection inspection
- Diagnosing undercharge and overcharge conditions
Because this is the lightest domain by weight, it's a reasonable place to trim review time if you're pressed for a study schedule - but it should never be ignored entirely, since even a handful of missed questions here can shift a borderline score. For a full explanation of what score you actually need, see A6 Passing Score 2026.
Domain 4: Lighting Systems Diagnosis and Repair (12%)
Lighting systems account for about 12% of scored questions. Modern vehicles have moved well past simple headlight and taillight circuits, so this domain increasingly overlaps with the electronics-heavy content in Domain 5.
Lighting Systems
Covers exterior and interior lighting circuits, including adaptive and automatic systems.
- Headlight, taillight, and marker light circuit diagnosis
- Automatic and adaptive headlight systems
- Interior lighting circuits
- Lighting-related module communication and fault codes
Circuit diagrams are especially common in this domain - you'll be expected to trace a lighting fault through a schematic rather than simply recall a definition.
Domain 5: Body Electrical Systems Diagnosis and Repair (34%)
Body Electrical Systems Diagnosis and Repair is the largest single domain on the A6 exam, accounting for 34% of scored questions - 17 out of 50. This is more than a third of your entire test, which means it deserves proportionally more of your study time than any other domain.
This domain is broad, covering several categories of vehicle systems:
Human Machine Interface (HMI) Systems
- Instrument clusters and driver information displays
- Infotainment and navigation system diagnosis
Comfort and Convenience Systems
- Power windows, locks, seats, and mirrors
- Heated and cooled seat/accessory circuits
Security Systems
- Anti-theft and immobilizer diagnosis
- Keyless entry and remote start circuits
Safety Systems
- Supplemental restraint systems (airbags)
- Wipers, horn, and speed control circuits
- Collision mitigation and telematics systems
- Head-up display, park assist, and camera systems
Because Domain 5 spans everything from airbags to backup cameras, it rewards technicians who have hands-on exposure to a wide range of modern vehicle electronics - not just older mechanical-electrical systems. If your shop experience is heavier on powertrain or brake work, this is the domain where dedicated study time matters most.
How the Domains Show Up in Question Format
Regardless of domain, A6 questions are written in workshops by national panels of working technicians, manufacturers, and educators, and they follow three recurring formats:
- Direct multiple choice - straightforward diagnostic or knowledge questions.
- Technician A / Technician B - two proposed diagnoses or repairs, and you decide which (if either) is correct.
- EXCEPT questions - you identify the one answer that does NOT belong among otherwise valid options.
Across all five domains, questions are frequently built around circuit diagrams and digital multimeter readings, so being able to read a schematic quickly and interpret a voltage or resistance value under time pressure is a skill that pays off in every domain, not just Domain 1. The exam is also offered with side-by-side Spanish and English text plus a pop-up bilingual glossary at no extra cost, which is worth knowing if English is not your first language.
| Domain | Weight | Approx. Scored Questions (of 50) |
|---|---|---|
| Body Electrical Systems Diagnosis and Repair | 34% | 17 |
| General Electrical/Electronic System Diagnosis | 26% | 13 |
| Battery and Starting System Diagnosis and Repair | 18% | 9 |
| Lighting Systems Diagnosis and Repair | 12% | 6 |
| Charging System Diagnosis and Repair | 10% | 5 |
Mapping a Study Schedule to Domain Weight
Once you know the weighting, it makes sense to structure your remaining prep time around it rather than moving through the domains in whatever order they're listed. A simple approach: spend the most calendar time on the two heaviest domains (Body Electrical Systems and General Electrical/Electronic System Diagnosis, together 60% of the test), then rotate through the remaining three in the weeks leading up to your test date.
General Electrical/Electronic System Diagnosis
- Drill voltage drop, continuity, and resistance calculations
- Practice reading wiring schematics and tracing circuits
- Review data bus fault scenarios and module programming basics
Body Electrical Systems Diagnosis and Repair
- Work through HMI, comfort/convenience, security, and safety subtopics separately
- Focus extra time on supplemental restraint and camera/park-assist systems if unfamiliar
Battery and Starting + Lighting
- Review battery testing methods and starter circuit voltage drop procedures
- Practice lighting circuit schematics, including adaptive headlight systems
Charging Systems + Full Review
- Cover alternator output and regulation testing
- Run full-length practice tests covering all five domains
This kind of domain-weighted schedule is a starting point, not a rigid formula - adjust the weeks based on which content areas match your existing shop experience. For a more detailed week-by-week breakdown, see the A6 Study Guide 2026, and once you're ready to test your recall against realistic questions, our practice tests are organized by these same five domains.
Key Takeaway
Don't study the five domains in equal proportions. Allocate roughly a third of your review time to Body Electrical Systems, another quarter to General Electrical/Electronic System Diagnosis, and divide the rest among Battery/Starting, Lighting, and Charging in proportion to their smaller weights.
Frequently Asked Questions
Most candidates benefit from starting with General Electrical/Electronic System Diagnosis (26%), since its circuit-theory concepts - voltage drop, continuity, schematic reading - apply directly to every other domain, including the largest one, Body Electrical Systems.
At 34% of scored questions (17 of 50), Body Electrical Systems Diagnosis and Repair reflects how much of a modern vehicle's functionality - from infotainment to safety systems like collision mitigation and park assist - is now governed by electronics rather than purely mechanical systems.
The A6 certification test has 60 total questions, of which 50 are scored across the five domains and 10 are unscored research questions used to develop future exams. The domain percentages above apply only to the 50 scored questions.
The recertification test is shorter, at 25 questions in 45 minutes, and covers the same five content areas, but it draws from a condensed question set. Reviewing all five domains - with extra attention to Body Electrical Systems and General Electrical/Electronic System Diagnosis - remains the safest approach for recertification as well.
Registration, fee structure, and the quarterly testing windows are covered in detail in our A6 Certification Cost 2026 and A6 Exam Dates 2026 guides, while overall value considerations are addressed in Is the A6 Certification Worth It?