TheoryASE T6 Truck Electrical Prep Practice Questions
Free ASE T6 Truck Electrical Prep practice questions with answers and plain-English explanations. Browse the PDF, video and online mock test.
ASE T6 Truck Electrical Prep Questions
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Q1When diagnosing a circuit with a blown fuse, which of these tools is MOST effective for finding the short to ground?
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✓ Correct answer: Digital multimeter (ohms)
A digital multimeter set to measure ohms is the most effective tool for finding a short to ground. By disconnecting components and measuring resistance to ground, a technician can isolate which component or section of wiring is causing the short.
Q2A truck's dash lights flicker intermittently while driving. Technician A says this could be caused by a loose battery connection. Technician B says this could be caused by a faulty alternator. Who is right?
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✓ Correct answer: Both A and B
Both technicians are correct. A loose battery connection can cause voltage fluctuations in the electrical system, resulting in flickering lights. Similarly, a faulty alternator that produces inconsistent output voltage would cause the same symptom.
Q3What is the proper way to measure voltage drop across a switch in a circuit?
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✓ Correct answer: Place meter leads on both sides of the switch with the circuit energized
To properly measure voltage drop across a switch, the circuit must be energized (on) with current flowing through it, and the multimeter leads must be placed on both sides of the switch simultaneously.
Q4When testing a truck that has a parasitic draw of 2.5 amps, what is the BEST next step?
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✓ Correct answer: Pull fuses one at a time while monitoring amperage
A parasitic draw of 2.5 amps is excessive and will quickly drain the battery. The best next step is to pull fuses one at a time while monitoring the amperage to isolate which circuit is causing the excessive draw.
Q5When diagnosing an open circuit, a technician connects one lead of an ohmmeter to one end of the circuit and the other lead to the opposite end. The meter reads OL (infinite resistance). What does this indicate?
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✓ Correct answer: There is an open somewhere in the circuit
An OL (infinite resistance) reading indicates there is no complete path for current to flow, confirming an open circuit exists somewhere between the two test points.
Q6What is the correct way to test a relay using a digital multimeter?
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✓ Correct answer: Check coil resistance and test continuity of contacts
To properly test a relay with a DMM, you should check coil resistance by measuring across the control terminals, and then verify continuity of the switch contacts both in their normal state and when the coil is energized.
Q7A truck's warning chime doesn't sound when the key is left in the ignition with the driver's door open. Using a wiring diagram, a technician determines that the circuit includes a door switch, ignition switch, and control module. What is the FIRST step in diagnosing this problem?
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✓ Correct answer: Test the door switch for proper operation
The first step should be to verify that the door switch is functioning correctly by checking if it shows continuity when the door is open. This is the logical starting point as it's one of the input sensors for the warning chime circuit.
Q8When reading a wiring diagram, a wire is labeled "BRN/WHT 141." What does this typically indicate?
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✓ Correct answer: A brown wire with white stripe, circuit number 141
On wiring diagrams, the color code typically indicates the wire's color (in this case brown with a white stripe) and the circuit or wire number (141), which helps identify specific wires in the harness.
Q9A technician is diagnosing a multiplexed data network issue on a truck. The diagnostic tool shows communication with some modules but not others. What is the MOST likely cause?
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✓ Correct answer: Open circuit in the data bus wiring
When some modules communicate but others don't in a multiplexed network, the most likely cause is an open circuit in the data bus wiring that is preventing communication with specific modules while allowing others to function.
Q10A circuit protected by a 10-amp fuse keeps blowing the fuse when operated. After replacing several fuses, what should be measured FIRST to diagnose the problem?
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✓ Correct answer: Circuit current draw with an ammeter
The first measurement should be circuit current draw with an ammeter. This will show if the circuit is drawing excessive current (above 10 amps) which would explain why the fuse keeps blowing, and help determine if there's a short or overload condition.
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