Five free practice questions on gauges, cab accessories and safety systems: content area E of the ASE T6 Electrical/Electronic Systems test, 12 of its 50 scored questions (24%). 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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Since a body upfitter installed a back-up alarm on a box truck, the alarm beeps whenever the key is on, in every gear, while the back-up lamps light only in reverse. The alarm has a feed wire and a ground wire to the frame. Which of these could be the cause?
- A back-up lamp switch stuck in its closed position
- An alarm feed tapped into an ignition-fed circuit
- An open in the alarm's ground wire to the frame
- A short between the back-up lamp wire and an ignition feed
Show the answer
B. Correct. The alarm sounds whenever it has power, and it now has power whenever the key is on, while the back-up lamps follow the switch correctly. Its feed was connected to a circuit that is hot in run instead of to the back-up lamp output; move the feed to the back-up lamp circuit with a proper splice.
Why not the others
A. A stuck-closed switch would light the back-up lamps in every gear too, but they light only in reverse. The alarm alone is powered all the time, so its own feed is on the wrong circuit.
C. An open ground stops current through the alarm, so it would be silent, not sounding all the time. An alarm that beeps with the key on in every gear is being fed from an ignition-hot circuit.
D. A short from an ignition feed onto the back-up lamp wire would light the lamps whenever the key is on, but they light only in reverse. Only the alarm is powered all the time, from its own misplaced feed.
ID T6-E-008 · Task T6-E-4 (ASE task list)
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A two-speed permanent-magnet wiper motor has three brushes: a common brush, a low-speed brush and a high-speed brush. Why does the motor run faster when current is fed through the high-speed brush?
- Its current strengthens the magnets, so torque rises
- It bypasses a resistor, so more voltage reaches the armature
- Fewer windings are in its path, so counter-voltage falls
- It feeds a second winding, so the two windings add
Show the answer
C. Correct. The high-speed brush sits offset from the low-speed brush, so fewer armature windings are in series between it and the common brush. Those fewer windings generate less counter-voltage as they turn, so the armature must spin faster before current and speed balance; the trade is less torque on high.
Why not the others
A. Current through the brushes does not add to the permanent magnets, and a stronger field would actually slow a DC motor by raising counter-voltage. High speed comes from fewer armature windings between the brushes.
B. A permanent-magnet three-brush motor has no speed resistor; its two speeds come from where the brushes sit on the commutator. The offset high-speed brush puts fewer windings in the current path, lowering counter-voltage.
D. There is one armature winding set, not two, and adding windings in the path would raise counter-voltage and slow the motor. The high-speed brush puts fewer windings in the path, so the motor runs faster.
ID T6-E-014 · Task T6-E-8 (ASE task list)
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Why does a door lock module energize the lock actuators for only a fraction of a second for each lock or unlock command, instead of holding them on while the switch is held?
- Actuators held on past their stroke would overheat
- A short pulse keeps the module's relay contacts from welding
- The module must free the circuit to read the door switches
- The battery cannot supply all the actuators for longer
Show the answer
A. Correct. A lock actuator moves the latch in a fraction of a second and then stalls against its stop; held on, it keeps drawing stall current and its small motor or solenoid overheats. A timed pulse completes the stroke and protects the actuator and the module's drivers.
Why not the others
B. Contact wear depends on the current switched at each opening and closing, which a short pulse does not reduce. The pulse is timed to protect the actuators, which would overheat if held energized.
C. The door and lock switches are read on their own input circuits, not through the actuator wires. The short pulse exists because actuators are built for momentary duty.
D. The battery and charging system can easily supply the actuators' current for longer than a pulse. The pulse is short because the actuators overheat if left energized after they reach their stops.
ID T6-E-023 · Task T6-E-18 (ASE task list)
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A truck's power door locks are all dead: neither door switch nor the remote operates any of them, and no actuator can be heard. Any of these could be the cause EXCEPT:
- a lost ground at the lock control module.
- an open fuse feeding the lock control module.
- an open in the driver's lock switch wire.
- an internal failure of the lock control module.
Show the answer
C. Correct. An open in one switch's wire would stop only that switch's commands; the passenger switch and the remote would still lock and unlock every door. Every lock dead from every input points to something they share: the module's feed fuse, its ground or the module itself.
Why not the others
A. This could cause it. The module's ground is shared by all its outputs and its own electronics, so losing it stops every actuator.
B. This could cause it. Without its feed, the module cannot power any actuator, so every lock is dead from every input.
D. This could cause it. The module drives all the actuators for the switches and the remote, so its failure leaves every lock dead.
ID T6-E-031 · Task T6-E-17 (ASE task list)
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This tractor has electronic stability control, and its collision mitigation system can apply the service brakes automatically when a crash with a slower vehicle ahead is about to happen. How does it apply them?
- By engaging the transmission's output retarder alone
- By venting the spring brake chambers' hold-off air
- By applying the trailer brakes through the hand valve
- By commanding the antilock system's air valves
Show the answer
D. Correct. The collision mitigation controller requests braking from the ABS/ESC system, whose modulator and active braking valves can already apply the service brakes without the driver, as they do in a stability event. It can also cut engine torque and apply the engine retarder.
Why not the others
A. A retarder slows the truck but is not the service brakes, and it cannot produce the deceleration needed to avoid a crash. The system applies the service brakes through the ABS/ESC valves.
B. Applying the spring brakes is a parking and emergency function, not a controlled deceleration, and it would lock the brakes rather than modulate them. Automatic braking is done through the ABS/ESC valves.
C. The trailer hand valve is a manual control in the cab with no electrical actuator. Automatic braking is applied through the ABS/ESC system's valves, which can brake the tractor and signal the trailer.
ID T6-E-036 · Task T6-E-23 (ASE task list)
02Answer key
| Question | Answer |
|---|---|
| Q1 | B |
| Q2 | C |
| Q3 | A |
| Q4 | C |
| Q5 | D |
03What area E covers
This content area covers the truck systems that work alongside the core electrical circuits: gauges, clusters and warning devices, horns and air bags, wipers and washers, heated mirrors, HVAC electrical parts, power outlets, windows and door locks, inverters, shore power and auxiliary power units, cruise control, cooling fan and fuel pump controls, ELDs and telematics, collision mitigation and backup cameras.
The ASE test specification calls this content area “Related Vehicle Systems Diagnosis and Repair”. It carries 12 of the 50 scored questions, 24% of the test.
- Diagnose gauges, clusters, senders and warning devices
- Program replacement clusters for the truck's configuration
- Test horns, air bag circuits, wipers and washers
- Check heated mirrors, A/C clutch circuits and power outlets
- Diagnose power windows and electric door locks
- Test inverters, shore power and auxiliary power units
- Check cruise, cooling fan and fuel pump control circuits
- Service ELDs, telematics, collision mitigation and cameras
04What the questions turn on
When every data gauge drops out
When every J1939-fed gauge drops out at once while a service tool still reads the engine ECM, the fault is in the cluster's own link to the backbone, not a sensor. A replacement cluster also needs the truck's configuration programmed before some gauges work.
Full voltage at a dead load
A load that does not work with full voltage across its own terminals, read while connected and switched on, has a good feed, switch and ground. The fault is in the part itself, such as an open washer pump or a window motor dead spot.
Inverter current on the DC side
An inverter's DC draw is its AC output divided by its efficiency, then by battery voltage: a 1,000-watt load at 90 percent takes about 92.6 amps at 12 volts. So an inverter needs heavy cables, a fuse near the battery and a capable bank.
Check what the ECM sees first
Cruise control and the electric fuel transfer pump answer to the engine ECM's own conditions. The scan tool shows what it sees and commands: a pump that primes but is commanded off during cranking points to a missing engine speed signal, not a bad pump.
05The other content areas
The T6 test has five content areas. Each has its own page of free questions:
The ASE T6 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, 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.