20 Electrical Systems Practice Questions & Answers

1. 1. A steering wheel is being removed on a vehicle equipped with a supplemental restraint system (SRS). Which practice follows the accepted procedure for disabling the air bag system before the work begins?

   • A.Pull the air bag fuse and start work as soon as the warning lamp stops glowing.
   • B.Leave the battery connected and simply unplug the yellow connector at the inflator.
   • C.Disconnect the positive battery cable and start work as soon as the clamp is off.
   • D.Disconnect the negative battery cable, then wait the manufacturer's specified time.✓ Answer

   Disabling an SRS means cutting its power and then letting the reserve energy stored in the module bleed off, which is why the published procedure is to disconnect the negative cable first and then wait the manufacturer's specified interval. Pulling a fuse or unplugging a connector on a live system leaves that stored energy available to fire the inflator.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — disarming and re-enabling the air bag systemReport a problem with this question

2. 2. Technician A says that after the battery is reconnected, the SRS warning lamp should light briefly at key-on and then go out, and that this self-check indicates the system is armed and working. Technician B says that if the SRS lamp stays on after the reconnection, the vehicle can still be released as long as the air bag connectors were plugged back in. Who is right?

   • A.Both Technician A and Technician B
   • B.Technician A only✓ Answer
   • C.Technician B only
   • D.Neither Technician A nor Technician B

   A momentary lamp illumination at key-on followed by the lamp going out is the module reporting that its self-test passed, so Technician A describes the correct verification. A lamp that stays on means a fault is stored and the restraint may not deploy in a crash, so the vehicle cannot be released in that condition and Technician B is wrong.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — verifying air bag warning lamp operation after serviceReport a problem with this question

3. 3. A voltage drop test is performed on the insulated side of the cranking circuit. With the engine cranking, the voltmeter is connected from the battery positive post to the starter B+ stud and reads 0.9 V. The service information allows a maximum of 0.2 V across that cable. What does the reading show?

   • A.The reading is acceptable because it is far below the 12 V available at the battery posts.
   • B.The battery is discharged and the cable should be retested after a full recharge cycle.
   • C.The starter is drawing more current than normal and should be removed and bench tested.
   • D.The cable and its connections have excessive resistance and must be cleaned or replaced.✓ Answer

   A voltage drop test measures the voltage consumed by resistance in a conductor while the circuit carries its normal current. Any drop above the published maximum means the cable or its terminals are absorbing voltage the starter needs, so they are cleaned or replaced and the test repeated. The same cable can measure near zero ohms when unloaded, which is why the loaded voltage drop is the preferred test.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — checking voltages, grounds and voltage drops and interpreting readingsReport a problem with this question

4. 4. With the engine cranking, a technician connects the voltmeter's negative lead to the battery negative post and the positive lead to the starter housing. The meter reads 0.6 V; the specification for the ground side is 0.2 V maximum. Which service action does this call for?

   • A.Clean and retighten the ground cable ends and the engine-to-body ground connections.✓ Answer
   • B.Replace the starter motor, since the drop proves the armature windings are shorted.
   • C.Charge the battery overnight, since the drop is caused only by a low state of charge.
   • D.No action, since a ground circuit is expected to drop more voltage than a feed circuit.

   The ground side of the cranking circuit is tested exactly like the insulated side, and 0.6 V against a 0.2 V maximum means the return path is adding resistance. The correct service is to clean and retighten the battery ground end, the engine-to-body strap and the starter mounting surface, then retest — not to condemn the starter or the battery on a ground-circuit reading.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — checking grounds and voltage drops and interpreting readingsReport a problem with this question

5. 5. A technician must measure both the current flowing in a lighting circuit and the voltage available at the lamp socket. How are the two meters connected?

   • A.Both meters go in series so that identical circuit current passes through each of them.
   • B.The ammeter goes in series with the circuit and the voltmeter in parallel at the socket.✓ Answer
   • C.The ammeter goes in parallel across the load and the voltmeter goes in series with it.
   • D.Both meters go in parallel so that neither meter can interrupt the circuit's current.

   Current has to pass through an ammeter, so the meter becomes part of the circuit and is wired in series (or a clamp is placed around the conductor). Voltage is a difference between two points, so a voltmeter is connected in parallel across the points of interest. Reversing the two puts a near short circuit across the load or an unwanted open in series with it.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — checking current flow and voltage in circuits and componentsReport a problem with this question

6. 6. An ohmmeter is to be used to check a length of harness wiring for continuity. Which condition must be satisfied for the reading to be valid?

   • A.The circuit must be powered so the meter can compare its reading against system voltage.
   • B.The circuit must be de-energized and the wire isolated from the rest of the harness.✓ Answer
   • C.The circuit must be under load so that current flows through the wire during the test.
   • D.The circuit must be grounded at both ends so the meter has a complete path to read.

   An ohmmeter supplies its own small test current, so any outside voltage gives a false reading or damages the meter, and any parallel path left through the rest of the harness reads as lower resistance than the wire actually has. The circuit must therefore be de-energized and the conductor isolated at both ends before the reading means anything.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — checking continuity and resistance and interpreting readingsReport a problem with this question

7. 7. A battery has just been taken off a charger and its open-circuit voltage reads 12.9 V. Before that reading can be used to judge state of charge, the technician should:

   • A.record 12.9 V as the state of charge and move straight on to the load test.
   • B.crank the engine for several seconds and take the reading with the key still on.
   • C.apply a brief load to remove the surface charge, let the voltage settle, then reread.✓ Answer
   • D.continue charging until the open-circuit voltage climbs above 13.0 V and holds.

   A battery just off a charger carries a surface charge that reads higher than its true state of charge. Applying a brief load and letting the voltage stabilize removes it so the open-circuit reading reflects the actual charge. Open-circuit voltage indicates state of charge only; state of health still requires a load or conductance test afterward.

   Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — battery state of charge and open-circuit voltage testingReport a problem with this question

8. 8. A battery is being tested. Technician A says a battery whose open-circuit voltage is 12.2 V can be load tested exactly as it sits, because a load test reports state of health rather than state of charge. Technician B says the standard load test applies one half of the battery's cold cranking amps (CCA) rating for 15 seconds. Who is right?

   • A.Technician B only✓ Answer
   • B.Both Technician A and Technician B
   • C.Technician A only
   • D.Neither Technician A nor Technician B

   A load test does report the battery's ability to deliver current, but a discharged battery will fail it regardless of its true condition, so the procedure requires the battery to be at or near full charge before the test is run — Technician A is wrong. Technician B states the standard test correctly: half the CCA rating held for 15 seconds while watching terminal voltage.

   Source: SAE J537 battery testing practice; Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — battery load and capacitance testingReport a problem with this question

9. 9. Battery ratings printed on the label are defined by published standards. Cold cranking amps (CCA) states the current a fully charged battery can supply:

   • A.for 30 seconds at 80 °F while terminal voltage stays above the standard minimum.
   • B.for 30 seconds at 0 °F while terminal voltage stays above the standard minimum.✓ Answer
   • C.for 25 minutes at 0 °F before terminal voltage falls to the standard minimum.
   • D.for 25 minutes at 80 °F before terminal voltage falls to the standard minimum.

   Cold cranking amps is defined by the published battery-rating standard as the current a fully charged battery delivers for 30 seconds at 0 °F while terminal voltage stays above the standard minimum, which is why it describes cold starting ability. The rating expressed in minutes at 80 °F is reserve capacity, a different measurement of how long the battery can carry a small load with the charging system out.

   Source: SAE J537, storage battery rating definitions for cold cranking amps and reserve capacityReport a problem with this question

10. 10. Service information calls for a memory saver to be connected before the battery cables are removed. What does that device accomplish?

    • A.It limits inrush current so fusible links do not open when the cables are refitted.
    • B.It maintains keep-alive voltage so modules retain learned settings and adaptive values.✓ Answer
    • C.It energizes the generator field so residual magnetism is not lost while power is off.
    • D.It bonds the body to ground so static cannot damage the air bag inflator circuits.

    Disconnecting the battery removes the keep-alive feed that holds volatile memory in the control modules, which is why learned idle values, transmission adaptive strategy, radio presets and convenience settings are lost. A memory saver supplies that small standing current through an accessory socket or the data link connector so nothing has to be relearned after the service is finished.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — maintaining or restoring electronic memory functionsReport a problem with this question

11. 11. All of the following are correct practices when disconnecting and reconnecting a vehicle battery EXCEPT:

    • A.Remove the positive cable first so the ground path stays available during the work.✓ Answer
    • B.Retorque the hold-down so the case cannot shift and put stress on posts and cables.
    • C.Remove the negative cable first so a wrench touching body metal cannot cause an arc.
    • D.Reconnect the negative cable last, after the positive cable is secured on its post.

    The negative cable is always removed first and reconnected last, because with the ground open a tool that slips onto body metal while at the positive post has no circuit to complete. Removing the positive cable first leaves the entire body energized as ground and creates exactly the arc the sequence exists to prevent, so that statement is the false one.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — battery removal, installation and cable serviceReport a problem with this question

12. 12. A battery has white powdery corrosion built up around both terminals and the cable clamps are pitted. Which service is correct?

    • A.Wash the deposits away with solvent and coat the clamps with heavy chassis grease.
    • B.Neutralize the deposits with a vinegar and water mixture, then rinse the top clean.
    • C.Neutralize the deposits with baking soda and water, then clean or replace the clamps.✓ Answer
    • D.Scrape the deposits off dry and refit the clamps without cleaning the post tapers.

    Battery-top corrosion is an acidic sulfate deposit, so it is neutralized with an alkaline baking soda and water solution; vinegar is itself an acid and will not neutralize it. Posts and clamps are then cleaned back to bright metal, or replaced where pitting remains, because a corroded contact surface adds resistance to the high-current cranking circuit.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — inspecting, cleaning and replacing battery cables, connectors, clamps and hold-downsReport a problem with this question

13. 13. A deeply discharged maintenance-free battery is going to be recharged in the shop. Why does the manufacturer's procedure favor a slow charge over a fast charge?

    • A.A low charging rate lets the charger stay connected with no attention to the battery.
    • B.A low charging rate removes the need for eye protection because no gas is produced.
    • C.A low charging rate dissolves sulfation faster than any high-current method can do.
    • D.A low charging rate limits heat and gassing while the plates take the charge back.✓ Answer

    Charge current beyond what the plates can absorb turns into heat and into the electrolysis that vents hydrogen, which warps plates and dries out a sealed maintenance-free case that cannot be refilled. A slow charge stays under that limit. Slow charging does not stop gassing altogether, so eye protection, ventilation and the manufacturer's stated rate and time still apply.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — slow and fast battery charging to the manufacturer's recommendationReport a problem with this question

14. 14. Jumper cables are being connected between a booster battery and a vehicle whose battery is discharged. Where is the final connection made?

    • A.On the positive post of the discharged battery in the disabled vehicle.
    • B.On the negative post of the booster battery in the assisting vehicle.
    • C.On the negative post of the discharged battery in the disabled vehicle.
    • D.On the engine ground of the disabled vehicle, away from the battery.✓ Answer

    Batteries vent hydrogen, and the last cable connected is the one that draws an arc as the circuit completes. Making that final connection at a solid engine ground well away from the battery keeps the spark away from the vented gas. Connecting last to the discharged battery's own negative post puts the arc directly over the cells.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — jump starting with a booster battery or auxiliary power supplyReport a problem with this question

15. 15. A starter current draw test is performed with a fully charged battery. The specification is 200 A maximum. The engine cranks slowly and the meter shows 105 A. What does the result indicate?

    • A.The starter circuit has high resistance, so cables, connections and grounds are suspect.✓ Answer
    • B.The neutral safety switch is open, so the control circuit must be replaced and retested.
    • C.The starter is drawing normal current, so the slow cranking must come from engine drag.
    • D.The starter armature is shorted internally, so the starter should be replaced at once.

    Current draw below specification combined with slow cranking means the motor is not receiving the current it needs, and the missing current is being lost to resistance in the feed, the ground or the connections; voltage drop testing on both sides of the circuit locates it. Draw above specification with slow cranking would point the other way, toward a dragging engine or a faulty starter.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — starter current draw test and interpretation of resultsReport a problem with this question

16. 16. An engine will not crank. Technician A says the starter control circuit on an automatic transmission vehicle is routed through a switch that permits cranking only in Park or Neutral. Technician B says a corroded connector in the control circuit can drop enough voltage that the solenoid will not pull in even though the battery is fully charged. Who is right?

    • A.Technician A only
    • B.Neither Technician A nor Technician B
    • C.Both Technician A and Technician B✓ Answer
    • D.Technician B only

    Both statements are correct. The control circuit on an automatic transmission vehicle is routed through a park/neutral position switch so the engine cannot crank in gear, and that circuit carries only the small solenoid pull-in current, so a corroded connector can drop enough of the available voltage that the solenoid never engages even with a good battery.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — inspecting starter control circuit switches, connectors and wiringReport a problem with this question

17. 17. A starter motor is about to be removed from the vehicle. Which step comes first?

    • A.Apply battery voltage to the S terminal to prove the solenoid before loosening the bolts.
    • B.Crank the engine briefly to bleed off the current stored in the solenoid pull-in winding.
    • C.Disconnect the positive battery cable only and leave the ground strap bolted to the block.
    • D.Disconnect the negative battery cable so the exposed B+ stud cannot short against ground.✓ Answer

    The starter's B+ stud is fed straight from the battery through an unfused cable, so the first step is to disconnect the negative battery cable; with the ground open, a wrench that bridges that stud and the vehicle structure cannot complete a circuit. Disconnecting only the positive cable leaves the ground path intact and the hazard exactly where it was.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — removing and replacing the starterReport a problem with this question

18. 18. A charging system output test is run at the engine speed given in the service information with an electrical load applied. System voltage measures 12.2 V against a specification of 13.5 to 14.8 V. This result identifies:

    • A.an undercharge condition, calling for the belt, connections and generator to be checked.✓ Answer
    • B.a normal condition, because voltage always drops below 13 V under an applied load.
    • C.a shorted battery cell, so the battery is replaced and the charging system passed.
    • D.an overcharge condition, calling for the voltage regulator to be replaced first.

    Voltage below the specified range with the engine running and a load applied means the generator is not replacing what the vehicle is consuming, which is an undercharge condition. The inspection follows the circuit in order: belt condition and tension, battery and generator connections and grounds, then generator output itself. Voltage above the range would be an overcharge and would point to regulation.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — charging system output test and identifying undercharge, no-charge and overcharge conditionsReport a problem with this question

19. 19. A serpentine belt that drives the generator is being inspected. Which finding makes the belt unserviceable?

    • A.A tensioner arm that swings smoothly through its travel and returns firmly to its stop.
    • B.A light film of belt dust on the pulley shields with every rib still square and intact.
    • C.Chunks torn out of the ribs and glazed, shiny sidewalls where they ride in the pulley.✓ Answer
    • D.A single chirp at cold start-up that clears once the engine reaches operating heat.

    The ribs are the belt's drive surface, so missing rib material, separation, or glazed contact faces that can no longer grip condemn the belt regardless of how many miles it has run. Belt dust with intact ribs, a tensioner that moves freely and returns to its stop, and a brief cold-start chirp are findings noted and monitored, not by themselves grounds for replacement.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — inspecting, adjusting and replacing generator drive belts, pulleys and tensionersReport a problem with this question

20. 20. All of the following are correct when replacing a halogen headlamp bulb and checking headlamp aim EXCEPT:

    • A.Handle the new bulb by its base so skin oil does not reach the quartz envelope.
    • B.Remove unusual cargo from the vehicle so ride height is normal while aim is checked.
    • C.Wipe the quartz envelope with bare fingers so any static charge can drain off first.✓ Answer
    • D.Set the tire pressures and park the vehicle on a level surface before checking aim.

    Skin oil left on a halogen bulb's quartz envelope creates a hot spot when the filament lights and cracks or shortens the life of the bulb, so the bulb is handled by its base only and never wiped with bare fingers. The other three statements are correct aiming preparation, because tire pressure, a level surface and normal vehicle load all determine ride height and therefore aim.

    Source: Official ASE Study Guide, Automobile Maintenance and Light Repair (G1) — inspecting, replacing and aiming headlights and bulbsReport a problem with this question

Practice questions based on the Test Specification and Task List published in the Official ASE Study Guide for the Automobile Maintenance and Light Repair (G1) test. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. ASE certification requires passing the test and documenting relevant work experience, and appropriate vocational training may count toward that experience — confirm current requirements with ASE before testing. No question here keys a manufacturer specification: torque values, clearances, pressures and capacities differ by vehicle, so any figure a question needs is given in the question itself, exactly as you would read it off a service manual on the job. About the ASE G1 test →