Five free practice questions on electrical diagnosis: content area A of the ASE A6 Electrical/Electronic Systems test, 13 of its 50 scored questions (26%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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What is a technical service bulletin (TSB)?
- The maker's chart of scheduled maintenance items
- A government order to perform a free safety repair
- A record of the past repairs made to one vehicle
- A maker's notice of a known problem and its fix
Show the answer
D. Correct. A TSB is issued by the vehicle manufacturer to describe a known pattern problem on certain vehicles and the updated diagnosis or repair, such as a revised part or a software update. Checking for one early can save hours of diagnosis.
Why not the others
A. The maintenance schedule lists service intervals; it is not a bulletin about a problem. A TSB describes a known problem on certain vehicles and the manufacturer's repair for it.
B. That is a misreading of a safety recall: a campaign to repair a safety defect free of charge, most often begun by the manufacturer itself rather than ordered by the government. A TSB is a manufacturer's notice of a known problem and its repair, and it is not a recall.
C. That is the vehicle's service history, which is also worth checking before diagnosis. A TSB is a manufacturer's notice about a known problem on a group of vehicles and its fix.
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A seat heater warms poorly. The manufacturer specifies 3.5 to 4.5 amps for the element at 12.5 volts. With the heater on, the voltage measured across the element's two terminals is 12.5 volts and the element's current is 1.2 amps. Which of these could be the cause?
- High resistance in the heater's feed circuit
- A heating element with excess resistance
- A corroded ground connection for the heater
- A shorted section in the heating element
Show the answer
B. Correct. The element has the full 12.5 volts across its own terminals, so the feed and ground are delivering; yet it passes only 1.2 amps, which means its resistance is about 10.4 ohms instead of roughly 2.8 to 3.6 ohms. The element itself has excess resistance and is replaced.
Why not the others
A. Feed resistance would drop voltage before the element, so the reading across the element's terminals would be less than 12.5 volts. Full voltage across the element rules out the feed.
C. Ground-side resistance would also take voltage away from the element, leaving less than 12.5 volts across its terminals. The element sees full voltage, so the ground is good.
D. A shorted section lowers the element's resistance, so it would draw more current than specified, not less. The element draws 1.2 amps, far below 3.5 amps, so its resistance is too high.
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A scan tool lists a DTC as a history (inactive) code. What does this mean?
- The code has been cleared but still shows in memory
- The fault is present now and the warning lamp is on
- The fault set earlier and is not present now
- The module could not finish testing that circuit
Show the answer
C. Correct. A history code records a fault the module saw earlier that is not present on the current check, often an intermittent. The failure-record or freeze-frame data stored with it helps recreate the conditions.
Why not the others
A. Clearing codes erases them, including history codes. A history code is a stored record of a fault that was detected earlier and is not present now.
B. That describes a current (active) code. A history code is a fault that set earlier and is not present now.
D. A test that has not run is shown as an incomplete or not-run status, not as a history code. A history code means the fault was detected earlier but is not present now.
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After the modules are asleep, a vehicle's key-off draw is 410 mA; the manufacturer allows 50 mA maximum. Removing one fuse drops the draw to 35 mA, and the wiring diagram shows that fuse feeds three circuits. What should the technician do next?
- Replace the module powered by that fuse
- Isolate each load on that fuse in turn
- Charge the battery and repeat the draw test
- Install a new fuse in that position and retest
Show the answer
B. Correct. The excess 375 mA is on that fuse, but the fuse feeds three circuits, so each load it supplies is isolated in turn until the draw falls within the limit. That identifies the one component or circuit staying on.
Why not the others
A. The fuse feeds three circuits, so the draw could be in any of them, such as a switch or lamp that stays on. Each load on the fuse is isolated before any part is replaced.
C. Charging does not change what is drawing current at key-off; the excess has already been traced to one fuse. The loads on that fuse are isolated one at a time.
D. The fuse is not the fault; it is simply the path the excess current takes. The loads it feeds are isolated one at a time to find the one drawing current.
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Unless a wiring diagram's notes say otherwise, in what state are its switches and relay contacts drawn?
- In their at-rest, not-actuated state
- In the actuated state that powers the circuit
- In the state they hold with the engine running
- Closed, so every current path can be traced
Show the answer
A. Correct. Diagrams normally show switches and relay contacts at rest, not pressed or energized, so a normally open contact is drawn open and a normally closed one closed. Knowing this tells the technician what should change when the part operates.
Why not the others
B. Diagrams show switches at rest, not actuated, so a normally open switch is drawn open even though it closes to power the circuit. The legend or notes say if a diagram differs.
C. Diagrams are not drawn with the engine running; switches and relay contacts are shown at rest, not actuated. The notes say if a diagram uses another state.
D. Drawing every contact closed would hide which ones are normally open. Switches and relay contacts are drawn at rest, so normally open contacts appear open.
02Answer key
| Question | Answer |
|---|---|
| Q1 | D |
| Q2 | B |
| Q3 | C |
| Q4 | B |
| Q5 | A |
03What area A covers
This content area covers the general skills behind every electrical repair: confirming the concern and checking service information, using a DMM, test light, current clamp and lab scope, reading wiring diagrams, finding opens, shorts and high resistance, measuring key-off battery drain, testing fuses, diodes and other protection devices, and diagnosing data networks and replacing or programming control modules.
The ASE test specification calls this content area “General Electrical/Electronic System Diagnosis”. It carries 13 of the 50 scored questions, 26% of the test.
- Verify the concern and research bulletins and recalls
- Measure voltage, voltage drop, current and resistance
- Read lab scope waveforms and scan tool data
- Locate opens, shorts and high-resistance faults
- Measure and trace key-off battery drain
- Test fuses, fusible links, circuit breakers and diodes
- Read wiring diagrams and their symbols
- Diagnose data networks, then replace and program modules
04What the questions turn on
Voltage drop needs current
A resistance drops voltage only while current flows through it, so even a corroded connection can read 0 volts with the circuit off. Voltage drop tests are made with the circuit switched on and loaded, where excess resistance shows as a measurable drop.
Ohmmeter readings can mislead
An ohmmeter's tiny test current cannot show a wire with only a few strands left. A part is measured isolated, since a parallel path lowers the reading, and on low readings the meter's own lead resistance is subtracted.
Let the modules sleep
After key-off, and again after the battery circuit is disturbed, modules stay awake and draw more than their sleep current. Battery drain is read after the manufacturer's wait time, and pulling fuses then shows which circuit carries the excess.
Ohms across a CAN bus
With the battery disconnected, about 60 ohms between CAN high and CAN low is normal: two 120-ohm terminating resistors in parallel. That reading cannot show a wire shorted to ground, so each wire is checked to ground separately.
05The other content areas
The A6 test has five content areas. Each has its own page of free questions:
The ASE A6 Electrical/Electronic Systems practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.