The ASE T6 Electrical/Electronic Systems test is part of ASE's Medium/Heavy Truck series. It has 50 scored questions in five content areas, plus 10 unscored questions, and you get 90 minutes for all 60. General electrical/electronic diagnosis is the biggest area at 14 questions (28.0%), then related vehicle systems at 12 (24.0%) and battery and starting at 11 (22.0%). Charging has 7 questions (14.0%) and lighting 6 (12.0%). Diagnosis and related vehicle systems together are 26 of the 50 scored questions. The task list runs from meter readings, schematics and the data bus to low voltage disconnects, cranking inhibit, trailer lighting, auxiliary power units and electronic logging devices. Questions are four-option multiple choice, including Technician A / Technician B and EXCEPT items. A pass plus 2 years of documented work experience certifies you for 5 years, and T6 is one of the seven tests, T2 to T8, for Master Medium/Heavy Truck Technician.
01The test specification
The ASE test specification for ASE T6 Electrical/Electronic Systems splits the 50 scored questions across five content areas. ASE adds 10 unscored questions for research, and you have 90 minutes for all of them. Each area links to five free questions.
| Area | Content area | Scored questions |
|---|---|---|
| A | General Electrical/Electronic System Diagnosis | 14 (28%) |
| B | Battery and Starting System Diagnosis and Repair | 11 (22%) |
| C | Charging System Diagnosis and Repair | 7 (14%) |
| D | Lighting Systems Diagnosis and Repair | 6 (12%) |
| E | Related Vehicle Systems Diagnosis and Repair | 12 (24%) |
| Total | 50 |
02What is the ASE T6 Electrical/Electronic Systems test?
T6 is the electrical test in ASE's Medium/Heavy Truck series. Its task list covers electrical diagnosis on trucks: meter and scan tool work, wiring schematics and the multiplexed data network, batteries and starting systems, charging, truck and trailer lighting, and a long list of related systems from gauges, wipers and door locks to auxiliary power units, telematics and safety systems.
It is a separate test from A6, ASE's electrical test for cars and light trucks, with its own task list. If you work on both, the A6 study guide covers the car and light-truck test.
T6 has 50 scored questions and 10 unscored ones, 60 in all, and you get 90 minutes. Every question is multiple choice with four options, (A) to (D). ASE adds the unscored questions to gather statistics for future tests, and you cannot tell which ones they are, so answer every question as if it counts.
Passing is one half of certification. ASE also asks you to document relevant work experience, which is 2 years for the tests in this series, and its truck study guide says suitable vocational training may count toward it; the details are at workexp.ase.com. The study guide does not publish a passing score. Once certified, you hold the certification for 5 years, and you renew it with a shorter recertification test, which for T6 is 25 questions in 45 minutes.
ASE's truck study guide marks T2 to T8 as the tests you need for ASE Certified Master Medium/Heavy Truck Technician status. T1, Gasoline Engines, is in the series but is not one of them. T6 is one of the seven.
03What does each content area cover?
The five areas list 68 tasks between them. ASE says every question represents one or more tasks, but not every task has to show up on the version you sit. Here is what each area asks you to know, in plain words.
Area A: General Electrical/Electronic System Diagnosis (14 questions)
Twelve tasks cover the core diagnostic skills. You measure source voltage and voltage drop, current flow (with a meter or a clamp-on ammeter), and continuity and resistance, and you track down opens, shorts and unwanted grounds. You find what is draining the batteries with the key off. You check circuit protection, from fuses and fusible links to circuit breakers, including resetting it where the design calls for that, and you test spike suppression parts (diodes, resistors and capacitors) as well as relays and solenoids, solid state types included. The list also covers reading schematics and their symbols, diagnosing faults on the multiplexed data bus, using scan tools, software and service information to read and record codes and to check parameters and calibration settings, and reading waveforms.
Area B: Battery and Starting System Diagnosis and Repair (11 questions)
Fifteen tasks cover the batteries and the starter. On the battery side: state of charge from the voltage at the posts, load and capacitance testing, cables, terminals, battery boxes, mounts and hold-downs, charging by the method that suits the battery (absorbed glass mat, lead acid and super capacitors are named), jump-starting from a booster battery or an auxiliary power supply, and low voltage disconnect (LVD) systems. On the starting side: watching voltage during cranking, voltage drop tests on the starting circuit, the starter control circuit and its over-crank protection, cranking inhibit systems, the starter itself with its relays and solenoid or integrated MAG switch (IMS), the flywheel ring gear or flex plate, and telling an electrical fault from a mechanical one when the engine cranks slowly, cranks only sometimes, will not crank, cranks too long or makes noise while cranking.
Area C: Charging System Diagnosis and Repair (7 questions)
Seven tasks, so about one question per task. You confirm that the charging indicators on the dash work, diagnose no-charge, low-charge and overcharge conditions, and service the alternator mounting and drive: belts or gears, pulleys, fans, brackets and tensioners. You test output voltage, both AC and DC, and output current, run voltage drop tests on the charging circuit, repair its wiring and connections, and test the alternator (generator) and whatever controls it, whether a regulator or a control module.
Area D: Lighting Systems Diagnosis and Repair (6 questions)
Eleven tasks. They start with exterior lights that are too bright, come and go or do not work, daytime running lights included, and with replacing and aiming headlights and auxiliary lights. Then come the circuits: headlight and dimmer switches, truck and trailer lighting (bulbs and LEDs alike), instrument lighting, interior cab lights, stoplights, turn signals and hazards with their flashers or electronic controls, and backup lights and backup warning devices. The last task is the trailer light cord itself, its connector and cable.
Area E: Related Vehicle Systems Diagnosis and Repair (12 questions)
This area has 12 questions but 23 tasks, the longest list on the test. The instrument tasks cover gauges that read high, low, wrong, now and then or not at all, on both conventional and electronic clusters, along with sending units, sensors, warning lights and buzzers, and checking that electronic instrumentation is calibrated for the vehicle. The body and cab tasks cover the horn, the airbag circuit and clock spring, wipers (including speed and park problems) and washers, motorized and heated mirrors, the electrical side of heating and A/C (compressor clutches, blower motors, resistors, sensors and control modules), power outlets and the lighter, power windows and electric door locks. The truck-specific tasks cover inverters, shore power and auxiliary power units, HVAC units included; cruise control; engine cooling fan controls; electric fuel supply or transfer pump controls; telematics and electronic logging devices (ELD); and safety systems such as speed control, collision avoidance and backup cameras.
04What kind of questions are on it?
ASE's truck study guide has seven T6 sample questions, and they show four styles.
Reading a meter on a diagram
Three samples come with a figure. In one, a meter is connected into a charging system diagram, with the alternator, the power distribution center and the engine control module, and you identify what it is measuring with the engine running. In another, you get a set of voltage readings taken across two batteries during cranking and decide what they say about the batteries. The third is a horn relay diagram with numbered relay terminals. Knowing where each meter lead sits, and what a working circuit should read at that point, is the skill all three test.
Technician A / Technician B
Two samples use this format. One is about headlights that are dim on high beam but normal on low beam, and the other is about horns that only sound when the relay is bypassed with a jumper wire. Each technician makes a claim and you decide whether A, B, both or neither is right; in these two samples one answer is neither and the other is A only, so do not assume one of them must be right. The method is in how to answer Technician A / B questions.
Which of these could be the cause?
Two samples give a symptom and four possible causes: a cab heater blower that runs only at low speed, and trailer marker lights that go dim at night when the driver brakes. The trailer question is a good example of a truck-only topic, since ASE's keyed answer points to the trailer light cord.
EXCEPT questions
One sample asks which of four conditions would NOT cause low alternator output, and the study guide prints a warning line above it telling you the question contains the word EXCEPT. Three options are possible causes and you pick the one that is not. Read these slowly.
05Where should your study time go?
Area A is 14 of the 50 scored questions (28.0%) and area E is 12 (24.0%): 26 of 50 (52.0%) between them. Add area B's 11 (22.0%) and three areas hold 37 of the 50 (74.0%). Charging and lighting make up the other 13 (26.0%). Batteries, starting and charging together are 18 questions (36.0%).
Area A is the toolkit for the rest of the test. Voltage drop, current and resistance checks, schematics and scan data are how you answer the battery, charging, lighting and related systems questions, so time spent on area A pays twice.
Area E is broad rather than deep: 23 tasks for 12 questions, so there are fewer questions than tasks and not every task will appear on your test. Learn how each system is wired and controlled (a switch or sensor input, a relay or module, a motor or actuator output) rather than memorizing parts. Area C is the opposite: 7 tasks for 7 questions, so each charging task matters.
Use the task list as a checklist and mark each task you could explain to someone else. Pace: 60 questions in 90 minutes is 1 minute 30 seconds each, which leaves time to trace a diagram.
06Registering, retesting and recertifying
You register and pay through ase.com. ASE charges a $34 registration fee per order plus $62 for each test, so T6 on its own comes to $96, and each extra test in the same order adds $62. Check ase.com for the current fees and dates before you book. The full breakdown is in ASE test fees and registration.
The test is delivered on screen. ASE's study guide points to a demonstration of its testing platform at ase.com/free-test-drive, and it notes that every ASE test offers a pop-up glossary from English to Spanish. More on the format: how ASE tests work.
If you do not pass, ASE makes you wait 30 days before you can take the test again. Use the month on area A and area E, which together are 52% of the scored questions.
After you pass, the certification runs for 5 years. To renew it you take the T6 recertification test, 25 questions in 45 minutes; you are eligible for it only after passing the full T6 certification test once.
07Questions people ask
- How many questions are on the ASE T6 Electrical/Electronic Systems test?
- 60 questions in 90 minutes: 50 scored and 10 unscored. ASE uses the 10 unscored questions to gather statistics for future tests, and you cannot tell which ones they are, so answer all 60.
- What is the biggest content area on ASE T6?
- General Electrical/Electronic System Diagnosis, with 14 of the 50 scored questions (28.0%), followed by Related Vehicle Systems Diagnosis and Repair with 12 (24.0%). Battery and starting has 11, charging 7 and lighting 6.
- Is ASE T6 the same as the A6 electrical test?
- No. T6 is the electrical test in ASE's Medium/Heavy Truck series, with its own task list, and ASE's truck study guide lists it among the seven tests, T2 to T8, required for Master Medium/Heavy Truck Technician. A6 is the separate electrical test for cars and light trucks.
- What score do you need to pass ASE T6?
- ASE's study guide does not publish a passing score for T6. It publishes the content areas, the question counts and the task list. Check ase.com for how results are reported.
- How long does ASE T6 certification last?
- 5 years. To renew it you take the T6 recertification test, 25 questions in 45 minutes, which you can take only after passing the full T6 certification test once. Certification also needs 2 years of documented work experience.
- Is ToolboxPrep affiliated with ASE?
- ToolboxPrep is an independent study site, not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original, written from ASE’s published test specifications and task lists and other public sources. They are not actual ASE test questions and not recalled or “brain dump” questions. ASE is a trademark of its owner, and we never use the ASE logo. Standards and service information are cited, not reproduced.
08Sources
- ASE Medium/Heavy Truck Study Guide, 2026: the T6 test specification, question counts, testing time, recertification test length, the 2-year work experience requirement, the Master Medium/Heavy Truck test list, the task list this page paraphrases, and the sample-question formats
- ASE (ase.com): the $34 registration fee per order, the $62 fee per test, the 5-year certification period and the 30-day retest wait
The content areas and question counts were checked against ASE's published study guide on October 17, 2026, and the task descriptions paraphrase its task list. ASE's study guide is the final word. If you find one of ours out of date, tell us.
Related: free practice questions · ten free T6 questions · How ASE tests work · ASE test fees and registration · A6 study guide, the car and light-truck electrical test
09Practice for this test
ToolboxPrep T6 practice tests are weighted to the specification above, area by area, and every answer is explained, all four options. You can try five sample questions with no account.
Ten free questions per test, no account: free practice questions. How our questions are written and checked: how our questions are made.
ToolboxPrep is an independent study site, not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original, written from ASE’s published test specifications and task lists and other public sources. They are not actual ASE test questions and not recalled or “brain dump” questions. ASE is a trademark of its owner, and we never use the ASE logo. Standards and service information are cited, not reproduced.