22 A6 — Electrical / Electronic Systems Practice Questions & Answers

1. 1. A headlamp on one side is noticeably dim. Technician A says checking the ground wire with an ohmmeter on the unpowered circuit is the best way to find the added resistance. Technician B says a voltage drop test taken with the headlamps turned on will reveal it. Who is right?

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

   An ohmmeter pushes only a few milliamps through the joint, so a corroded or partially broken connection can still read near 0 ohms. A voltage drop test energizes the circuit at normal load current, and by E = I x R that same resistance produces a measurable voltage. This is why a resistance check can pass while the circuit still fails under load.

   Source: ASE A6 Task List, Area A: General Electrical/Electronic System Diagnosis - measure and diagnose voltage drops; diagnose high-resistance faultsReport a problem with this question

2. 2. A technician is measuring key-off battery drain (parasitic draw). Which action produces a valid reading?

   • A.Connect the ammeter in parallel across the two battery posts with both cables still attached
   • B.Connect the ammeter in series between the disconnected negative cable and the battery post, then wait for all modules to time out before reading✓ Answer
   • C.Read the current immediately, then open a door each time a fuse is pulled to watch the change
   • D.Crank the engine briefly with the meter connected to confirm the circuit is complete

   An ammeter must carry the circuit current, so it goes in series in the battery cable path. Modules stay awake after the doors are closed and typically need 20 to 60 minutes to enter sleep mode, so an early reading is falsely high. Opening a door or cranking wakes modules and can exceed the meter's fused current range.

   Source: ASE A6 Task List, Area A: measure and diagnose the cause(s) of excessive key-off battery drain (parasitic draw)Report a problem with this question

3. 3. Two 6-ohm resistors are connected in parallel across a 12-volt source. What is the total current drawn from the source?

   • A.2 A
   • B.12 A
   • C.1 A
   • D.4 A✓ Answer

   Two equal resistors in parallel give a total resistance of half of one branch, so 6 ohms and 6 ohms equal 3 ohms. Ohm's law I = E / R gives 12 V divided by 3 ohms, or 4 A. Total parallel resistance is always less than the smallest branch, so adding branches raises total current.

   Source: Ohm's law (E = I x R) and parallel circuit rules; ASE A6 Area A general electrical diagnosisReport a problem with this question

4. 4. With the key off and modules powered down, a DMM connected across data link connector terminals 6 and 14 reads about 120 ohms instead of the expected 60 ohms. What does this indicate on a high-speed CAN bus?

   • A.CAN High is shorted to CAN Low
   • B.One of the two 120-ohm terminating resistors, or the branch containing it, has been lost✓ Answer
   • C.This is the normal reading for a healthy bus
   • D.The bus is shorted to ground

   High-speed CAN uses a 120-ohm terminating resistor at each end of the twisted pair, and two 120-ohm resistors in parallel measure about 60 ohms. Reading roughly 120 ohms means only one terminator remains in the circuit, so a terminating resistor or the wiring to that module has opened. A reading near 0 ohms would instead point to a short between the two bus wires.

   Source: ASE A6 Task List, Area A: diagnose failures in the data bus communication network; ISO 11898 high-speed CAN terminationReport a problem with this question

5. 5. A 15-amp fuse for an accessory power outlet blows immediately every time it is replaced. Any of these could be the cause EXCEPT:

   • A.High resistance at the outlet's ground connection✓ Answer
   • B.A component in the circuit that is shorted internally to its case
   • C.A chafed feed wire touching bare sheet metal
   • D.A harness pinched against a bracket where the insulation is crushed through

   A fuse opens because current exceeded its rating, and unwanted current means a short to ground that bypasses the load. High resistance does the opposite: it reduces current, producing dim, slow or intermittent operation rather than a blown fuse. Installing a higher-rated fuse is never the repair, because the wiring is sized for the original fuse.

   Source: ASE A6 Task List, Area A: find shorts, grounds, opens and high-resistance problems; inspect and test fuses and current-limiting devicesReport a problem with this question

6. 6. With the brake pedal pressed and the stop lamps commanded on, a DMM connected across the two terminals of the brake lamp switch reads 12.5 volts. What does this reading mean?

   • A.The stop lamp ground circuit is open
   • B.The switch is closed and passing current normally
   • C.The switch contacts are open, so no current reaches the lamps✓ Answer
   • D.Both stop lamp bulbs have burned out

   Voltage appears across the point of highest resistance, and an open has effectively infinite resistance, so full source voltage measured across a device in a series path means the circuit is open at that device. A good closed switch should drop near 0 volts. If the bulbs or the ground were open instead, no current would flow and the meter across the closed switch would read about 0 volts.

   Source: ASE A6 Task List, Area A: measure and diagnose voltage and voltage drops; interpret electrical schematic readingsReport a problem with this question

7. 7. After surface charge is removed, a 12-volt lead-acid battery measures 12.2 volts open-circuit. What should the technician conclude?

   • A.The battery is roughly 50 percent charged and should be recharged before load testing✓ Answer
   • B.The battery is being overcharged by the charging system
   • C.The battery is fully charged; proceed directly to a load test
   • D.The battery has an internal short and must be replaced without further testing

   Open-circuit voltage tracks state of charge: about 12.6 V is full, 12.4 V is roughly 75 percent, 12.2 V is roughly 50 percent and 12.0 V is roughly 25 percent. A conventional load test is only valid on a battery that is at least about 75 percent charged, because a discharged battery will fail the test even if it is serviceable. A conductance or capacitance tester can evaluate a partially discharged battery.

   Source: ASE A6 Task List, Area B: perform battery state-of-charge test; perform battery capacity/load testReport a problem with this question

8. 8. An engine cranks slowly. A starter current draw test shows current well BELOW specification, and available voltage at the starter stays high during cranking. The most likely cause is:

   • A.A mechanically dragging or tight engine
   • B.Shorted field windings inside the starter
   • C.High resistance in the starter feed or ground circuit✓ Answer
   • D.A hydraulically locked cylinder

   Resistance limits current, so a corroded cable or connection starves the starter and produces low current draw with slow cranking while voltage upstream remains high. The opposite pattern, current draw above specification with slow cranking, points to engine mechanical drag or an internally faulty starter. The high-resistance fault is located with voltage drop tests on the loaded circuit, not with an ohmmeter.

   Source: ASE A6 Task List, Area B: perform starter current draw test; perform starter circuit voltage drop testsReport a problem with this question

9. 9. A start-stop vehicle needs a battery. Technician A says an AGM battery may be replaced with a conventional flooded battery of the same group size with no other steps. Technician B says many vehicles require the new battery to be registered or reset with a scan tool so the charging strategy matches the battery. Who is right?

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

   AGM and enhanced flooded batteries require a different charging profile than conventional flooded batteries, so substituting the wrong type leads to chronic undercharge and early failure. On systems that manage charging by battery state, the replacement must be registered or the state-of-charge algorithm reset per the manufacturer's procedure. Technician A's step is the one that causes the problem, not the fix.

   Source: ASE A6 Task List, Area B: identify low-voltage energy storage type and configuration; charge battery using manufacturer's recommended methodReport a problem with this question

10. 10. Technician A says a conventional battery load test applies a load of about half the CCA rating for 15 seconds, and the voltage must stay at or above about 9.6 volts at roughly 70 degrees F. Technician B says the battery must be at least about 75 percent charged before the load test is valid. Who is right?

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

    The industry-standard load test draws half the cold cranking amp rating (or three times the amp-hour rating) for 15 seconds while watching terminal voltage, and the 9.6-volt minimum is corrected downward as temperature drops. Both statements are independently true, so both technicians are right. A discharged battery cannot support the load and would fail the test even if it is serviceable.

    Source: ASE A6 Task List, Area B: perform battery capacity (load) test; perform battery state-of-charge testReport a problem with this question

11. 11. A charging system has low output. With the engine running and the electrical system loaded, a DMM set to AC volts reads 0.9 V AC at the battery terminals. The most likely cause is:

    • A.A failed diode in the rectifier bridge or an open stator winding✓ Answer
    • B.A discharged but otherwise good battery
    • C.An over-tightened drive belt
    • D.A loose battery hold-down

    The generator produces three-phase AC in the stator, and six diodes rectify it to DC, so a healthy system leaves only a small AC ripple. An open or shorted diode removes one phase, costing roughly a third of the output and leaving excessive AC ripple, generally more than about 0.5 V AC. A shorted diode can also let battery current flow backward into the generator with the key off, showing up as a parasitic drain on the B+ lead.

    Source: ASE A6 Task List, Area C: diagnose charging system problems; perform charging system output testReport a problem with this question

12. 12. A vehicle's charging voltage measures about 15.8 volts at idle and the battery is gassing and using water. Which condition best explains this?

    • A.A defective voltage regulator, or high resistance in the regulator's voltage-sense circuit✓ Answer
    • B.A glazed, slipping serpentine belt
    • C.High resistance in the battery-to-starter cable
    • D.An open diode in the rectifier bridge

    The regulator controls field current based on the voltage it senses, so if the sense or reference lead is resistive or poorly grounded the regulator sees an artificially low system voltage and raises output. An open diode or a slipping belt causes low output, not overcharge, and starter cable resistance affects cranking rather than regulation. Sustained voltage above roughly 15 volts overcharges the battery and can also make lamps burn brighter than normal.

    Source: ASE A6 Task List, Area C: diagnose charging system overcharge conditions; inspect and test generator control components including regulatorsReport a problem with this question

13. 13. After the rear turn signal bulbs are replaced with LED lamps, the turn signals on that side flash much faster than normal. What is the correct repair?

    • A.Add a second ground strap to the body
    • B.Install a higher-amperage fuse in the turn signal circuit
    • C.Replace the turn signal switch
    • D.Install a load resistor or an LED-compatible electronic flasher✓ Answer

    A current-sensing or thermal flasher sets its rate from the current the lamps draw, so losing a bulb or fitting low-current LEDs makes it flash fast, which is the built-in burned-out-bulb warning. Restoring the expected current with a load resistor, or using a flasher whose rate does not depend on load, corrects the flash rate. A larger fuse does not change the flash rate and defeats the circuit's protection.

    Source: ASE A6 Task List, Area D: diagnose turn signal and hazard light malfunctions; inspect and replace flasher unitsReport a problem with this question

14. 14. With the left turn signal operating, the left tail lamp and an unrelated side marker also glow dimly in step with the flasher. Technician A says a burned-out bulb elsewhere in the circuit is the cause. Technician B says a high-resistance or open shared ground can force current to feed back through another lamp's filament. 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

    Current always seeks a path back to the source, so when a shared ground is lost the energized circuit finds ground through the filament of a neighboring lamp, lighting it dimly because the two filaments are now effectively in series. This feedback or backfeed symptom is repaired by restoring the ground connection, not by replacing bulbs. A burned-out bulb causes a lamp not to light; it does not create the backfeed path.

    Source: ASE A6 Task List, Area D: diagnose the cause of intermittent, dim, continuous or no operation of exterior lighting; ground circuit diagnosisReport a problem with this question

15. 15. Both headlamps are noticeably dim at idle and at highway speed. Any of these could be the cause EXCEPT:

    • A.High resistance in the headlamp feed circuit or a burned connector
    • B.An undercharging charging system
    • C.A corroded shared headlamp ground connection
    • D.An overcharging voltage regulator✓ Answer

    Anything that adds resistance to a circuit shared by both lamps, or that lowers available system voltage, reduces the current through the filaments and dims them. Overcharging does the opposite: higher-than-normal system voltage makes lamps burn brighter than normal and shortens bulb life. Because both lamps are affected, the fault is in a shared feed, ground or the supply voltage rather than in one branch.

    Source: ASE A6 Task List, Area D: diagnose the cause of brighter-than-normal, dim, intermittent or no operation of exterior lightingReport a problem with this question

16. 16. Which procedure is correct before and during removal of a steering wheel airbag module?

    • A.Set the removed module face down on the bench so the trim cover cannot be scratched
    • B.Check the inflator circuit for continuity with a self-powered test light before removal
    • C.Disconnect the battery, wait the manufacturer-specified time for the reserve capacitor to discharge, carry the module with the trim side away from your body, and set it face up on the bench✓ Answer
    • D.Leave the battery connected so the module can be monitored with a scan tool during removal

    The SRS keeps a reserve energy capacitor charged so it can deploy briefly after power loss, so the battery must be disconnected and the specified wait time observed before service. A self-powered test light or ohmmeter sends current through the squib and can deploy the inflator, so those tools are never used on SRS circuits. A module set face down can launch itself if it deploys, so it is placed face up with the trim side away from people.

    Source: ASE A6 Task List, Area E: diagnose and service supplemental restraint systems (SRS); manufacturer SRS service precautionsReport a problem with this question

17. 17. The horn, the steering wheel audio controls and the driver airbag all stop working at the same time, and the SRS warning lamp is on. Technician A says a failed clockspring could account for all of these symptoms. Technician B says the clockspring must be centered or timed before installation or it will be damaged. Who is right?

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

    The clockspring is the ribbon-conductor coupling that carries horn, steering wheel control and airbag squib circuits across the rotating steering column, so one failed assembly can open several unrelated-seeming circuits at once. It has a limited number of turns, so if it is installed off center the ribbon tears when the wheel reaches full lock. Both statements are independently true.

    Source: ASE A6 Task List, Area E: diagnose and service safety systems including SRS, horn and steering wheel controlsReport a problem with this question

18. 18. The left rear power window works normally in both directions from its own door switch, but from the driver's master switch it will only go down. Technician A says the window motor is faulty. Technician B says an open in the master switch or in the wiring between the master switch and that door is likely. Who is right?

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

    A reversible window motor changes direction only because the ganged switch contacts reverse the polarity applied to its two leads. Since the motor runs both directions from the local switch, the motor, its feed and its ground are proven good, so the fault must be in the path that is unique to the master switch, meaning one set of master switch contacts or the wire carrying that polarity. Testing for voltage at the motor connector while the master switch is held in the failed direction confirms it.

    Source: ASE A6 Task List, Area E: diagnose comfort and convenience accessories including power windows; reversible motor and ganged switch operationReport a problem with this question

19. 19. One grid line of a rear window defogger does not clear. Probing along that line with a voltmeter shows about 12 volts from the feed side up to one point, then near 0 volts beyond it. What does this indicate?

    • A.The defogger relay or timer has failed
    • B.The grid line is broken at that point and can be repaired with conductive grid paint✓ Answer
    • C.The defogger ground connection is open
    • D.This is normal; a good grid line reads 0 volts along its length

    A working grid line carries current, so voltage tapers progressively from near full system voltage at the feed side to near zero at the ground side. An abrupt change from full voltage to zero means no current is flowing past that spot, which locates the open in the grid element. A failed relay, timer or ground would affect every line, not just one.

    Source: ASE A6 Task List, Area E: diagnose and service heated accessories including heated glassReport a problem with this question

20. 20. A coolant temperature gauge in the instrument cluster reads far lower than actual, but the scan tool coolant temperature PID matches an infrared thermometer reading of the engine. Technician A says the sensor or its circuit is at fault. Technician B says the cluster or display side is at fault because the data on the bus is correct. Who is right?

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

    On a networked vehicle the cluster usually does not read the sensor directly; it displays a value received over the data bus. A scan tool PID that agrees with a known-good independent measurement proves the sensor, its circuit and the sending module are producing correct data, so the error is downstream in the cluster or its display. If the PID itself were wrong, the sensor or its circuit would be the suspect instead.

    Source: ASE A6 Task List, Area E: diagnose human machine interface systems including instrument cluster and driver information systemsReport a problem with this question

21. 21. An engine cranks at normal speed but will not start, and the security or immobilizer indicator flashes while cranking. What is the most likely cause?

    • A.The instrument cluster bulb for the security lamp has failed
    • B.The starter solenoid contacts are burned
    • C.A restricted fuel filter is starving the engine
    • D.The transponder key or immobilizer module has not authenticated, so fuel or spark is disabled and a key relearn or module programming is required✓ Answer

    A flashing security indicator during cranking is the system reporting that it did not recognize a valid key, and the immobilizer strategy then disables fuel injection, spark or the starter as an anti-theft measure. The repair is key or module relearn and programming per the manufacturer's procedure, not replacing fuel or ignition parts. A fuel restriction or a bad solenoid would not command the security lamp to flash.

    Source: ASE A6 Task List, Area E: diagnose security/anti-theft systems including starter/fuel disable and keyless entryReport a problem with this question

22. 22. One door's power lock, power window and heated mirror all work intermittently, and the symptoms change when the door is opened and closed. What should be inspected first?

    • A.The wires in the flexible harness that passes through the door jamb boot✓ Answer
    • B.The window regulator adjustment
    • C.The vehicle battery state of charge
    • D.The body control module, which should be replaced and programmed

    Conductors inside the door jamb boot flex every time the door moves, so they work-harden and break inside the insulation, which explains multiple unrelated circuits in one door failing together and changing with door position. Wiggle testing the boot while monitoring the circuits confirms it before any module is condemned. A failed module or a weak battery would not be limited to one door or track with door movement.

    Source: ASE A6 Task List, Area E: inspect and service components and wiring of comfort and convenience accessories; intermittent wiring diagnosisReport a problem with this question

Practice questions written to the ASE Automobile & Light Truck (A-series) task lists and standard automotive service principles. ASE is a mark of the National Institute for Automotive Service Excellence; this site is not affiliated with or endorsed by ASE. Always follow the vehicle manufacturer's service information for specifications and procedures on a real repair. About the ASE tests →