Five ASE A6 Electrical/Electronic Systems practice test questions, answers included.

1. Recall · General Electrical/Electronic System Diagnosis

   When measuring key-off battery drain with an ammeter in series with the battery, why does the technician wait for the time given in the service information before reading the meter?

   1. Battery surface charge must bleed off before the draw is steady
   2. Modules stay awake after key-off and draw more until they sleep
   3. A DMM needs that time to settle on its milliamp range
   4. The generator's field must decay before its diodes stop leaking
   Show the answer

   B. Correct. After the key is turned off, and again after the battery circuit is disturbed, control modules stay awake for a while and draw far more than their sleep current. A reading taken before they sleep looks like an excessive drain; the wait time is the manufacturer's.

   Why not the others

   A. Surface charge affects an open-circuit voltage reading taken soon after charging; it does not change how much current the loads draw. The wait is for the modules to go to sleep.

   C. A DMM settles in seconds, and the amp or milliamp input is chosen by the jack and range the technician selects. The wait is for the vehicle's modules to go to sleep, not for the meter.

   D. The generator field collapses as soon as the engine stops. A leaking rectifier diode is a steady drain that does not go away with time. The wait is for the modules to go to sleep.

2. Diagnosis · Battery and Starting System Diagnosis and Repair

   A vehicle with an automatic transmission and a key-start ignition switch does not crank, and makes no click, when the key is turned to Start with the shift lever in Park. With the lever in Neutral it cranks and starts normally every time. Which of these could be the cause?

   1. A misadjusted transmission range switch
   2. A starter relay with burned contacts
   3. A worn start contact in the ignition switch
   4. A battery too discharged to crank
   Show the answer

   A. Correct. The transmission range switch closes the starter control circuit only in Park and Neutral, so a switch that is misadjusted or failed at its Park position opens the circuit in Park alone. Normal cranking in Neutral proves the battery, relay, ignition switch and starter can all do their jobs; adjust or replace the switch per the manufacturer's procedure and confirm cranking in both positions.

   Why not the others

   B. A relay with burned contacts would stop cranking in every shift position, because the same relay feeds the starter in Park and in Neutral. Normal cranking in Neutral shows the relay works; the fault is in the part of the control circuit that only Park uses, the range switch.

   C. A worn start contact in the ignition switch would leave the starter without a control signal whichever position the shift lever is in. Because the engine cranks every time in Neutral, the start contact is working; the range switch's Park contact is the suspect.

   D. A discharged battery would give slow cranking, clicking or no cranking in Neutral as well as in Park. The engine cranks and starts normally in Neutral, so the battery can crank it; the fault is in the Park side of the range switch.

3. EXCEPT · Lighting Systems Diagnosis and Repair

   Both low-beam headlamps are equally dimmer than normal with the engine running. Any of these could be the cause EXCEPT:

   1. high resistance at a ground splice shared by both headlamps.
   2. worn contacts in the relay that feeds both low beams.
   3. an open high-beam filament in the left headlamp bulb.
   4. charging voltage below the manufacturer's specification.
   Show the answer

   C. Correct. An open high-beam filament stops the high beam on that side but takes nothing from the low-beam filaments, which have their own feed terminal. Both low beams dimming together points to something the two lamps share: their feed, their ground or system voltage.

   Why not the others

   A. A shared ground splice carries both lamps' current, so resistance there lowers the voltage across both bulbs alike. This could cause the symptom; a voltage drop test on the ground side with the lamps on finds it.

   B. Burned or pitted relay contacts add resistance in series with the feed to both lamps, so both bulbs see less voltage and glow dimmer. This could cause the symptom.

   D. Lamp brightness follows system voltage; with the charging system putting out less than it should, every lamp, including both low beams, runs dimmer. This could cause the symptom.

4. Recall · Body Electrical Systems Diagnosis and Repair

   A navigation unit keeps moving the vehicle's position along the map while the car is in a long tunnel with no satellite signal. Which inputs let it keep estimating the position?

   1. The heading from the mirror compass alone
   2. Satellite radio signal strength at the antenna
   3. The last satellite fix and the elapsed time
   4. A vehicle speed signal and a yaw-rate sensor
   Show the answer

   D. Correct. With no satellite fix the unit uses dead reckoning: the speed signal tells it how far the vehicle has gone and a yaw-rate (gyro) sensor tells it how much the vehicle has turned. When the satellite signal returns, the unit corrects any drift.

   Why not the others

   A. A compass heading gives direction but no distance, so the unit could not tell how far along the road the vehicle had moved. It uses a speed signal with a yaw-rate sensor.

   B. Satellite radio carries audio, not position, and its signal is lost in a tunnel too. Position is carried forward from the speed signal and a yaw-rate sensor.

   C. Time alone cannot tell how far or which way the vehicle went; a stopped car and a moving one would look the same. The unit needs a speed signal for distance and a yaw-rate sensor for turns.

5. Diagnosis · Body Electrical Systems Diagnosis and Repair

   After a steering column repair, the heated steering wheel and the horn both stopped working and the air bag warning lamp stays on. The wiring diagram shows these three circuits share no fuse, relay, ground or control module. Which of these is the cause?

   1. A faulty SRS control module
   2. An open steering-wheel heater element
   3. A faulty horn switch in the wheel
   4. A damaged clockspring
   Show the answer

   D. Correct. The clockspring carries the steering-wheel heater, horn switch and driver air bag circuits across the turning joint between the column and the wheel, so it is the one part all three faults share. A clockspring that was off-center when the wheel was installed can tear its ribbon the first time the wheel is turned to a stop.

   Why not the others

   A. The SRS module does not power the horn or the wheel heater, so its failure could not stop them. Three unrelated circuits failing together point to the clockspring they all pass through.

   B. An open heater element would stop only the heated wheel. It cannot silence the horn or turn on the air bag lamp; the part common to all three circuits is the clockspring.

   C. A failed horn switch would affect only the horn. The heated wheel and air bag circuits do not use it, so the common fault is the clockspring that all three cross.

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