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Automotive Service Excellence (ASE) A6 Electrical/Electronic Systems practice questions

242 free questions with answers and explanations.

Practice test
  1. 51.A technician is diagnosing an intermittent starting issue. The starter motor occasionally fails to crank, but all dashboard lights illuminate brightly. A voltage drop test on the starter motor's main positive cable (from battery to starter) shows 0.1V during a successful crank. When the no-crank condition occurs, the technician measures 12V at the starter solenoid's S-terminal (control wire). What is the MOST likely cause?General Electrical/Electronic System Diagnosis
  2. 52.A technician is diagnosing an intermittent starting issue on a vehicle. The starter motor sometimes clicks but does not crank the engine. The battery has been tested and is fully charged. When the issue occurs, a voltage drop test across the starter solenoid's main power terminal to the battery positive post shows 0.1V. A voltage drop test from the starter motor's ground connection to the battery negative post shows 0.8V. Which of the following is the MOST likely cause of the intermittent starting issue?General Electrical/Electronic System Diagnosis
  3. 53.A vehicle's high-beam indicator light on the dashboard illuminates, but the high-beam headlights themselves do not turn on. The low-beam headlights function normally. The technician verifies that the high-beam fuse is good and there is battery voltage present at the high-beam relay's control side (pin 86). What should the technician check NEXT?Lighting Systems Diagnosis and Repair
  4. 54.A technician is diagnosing a vehicle with an illuminated battery warning light. The battery voltage is 12.4V with the engine off. With the engine running at 2000 RPM, the voltage at the battery terminals measures 12.2V. A voltage drop test between the alternator's B+ terminal and the battery's positive post shows 0.1V. What is the MOST likely cause of this condition?Charging System Diagnosis and Repair
  5. 55.A technician is diagnosing a vehicle with an intermittent 'Check Engine' light and a stored Diagnostic Trouble Code (DTC) for 'System Too Lean (Bank 1)'. Using a scan tool, the technician observes that the Short Term Fuel Trim (STFT) for Bank 1 is consistently around +15% and the Long Term Fuel Trim (LTFT) for Bank 1 is around +10%. What do these fuel trim values MOST likely indicate?General Electrical/Electronic System Diagnosis
  6. 56.A technician is diagnosing an intermittent issue with a vehicle's ABS system. The scan tool shows a C0035 (Left Front Wheel Speed Sensor) code. The technician uses an oscilloscope to capture the waveform from the left front wheel speed sensor while rotating the wheel by hand. The waveform shows a consistent, clean square wave with appropriate voltage swings, but sometimes it briefly disappears. What is the MOST likely cause?General Electrical/Electronic System Diagnosis
  7. 57.A vehicle's backup lights are inoperative, but all other lights on the vehicle work correctly. The technician checks the fuse for the backup light circuit and finds it to be good. When the transmission is shifted into reverse, a voltmeter connected to the backup light switch output wire shows 12V. What is the MOST likely cause?Lighting Systems Diagnosis and Repair
  8. 58.A technician is diagnosing a vehicle where the right front turn signal illuminates steadily but does not flash. The left turn signal operates normally, and the hazard lights flash correctly on both sides. The vehicle uses an electronic flasher relay. What is the MOST likely cause?Lighting Systems Diagnosis and Repair
  9. 59.A technician is diagnosing an intermittent starting issue where the engine cranks normally but occasionally fails to start. The fuel pump operates, and spark is present. Using a scan tool, the technician observes that the engine RPM signal is intermittently dropping to zero during cranking, even though the engine is clearly rotating. Which of the following components is the most likely cause?General Electrical/Electronic System Diagnosis
  10. 60.A technician is diagnosing an intermittent starting issue. The starter motor occasionally cranks normally, but sometimes there is a 'click' from the starter solenoid and no cranking. Battery voltage tests good, and a voltage drop test on the starter power cable shows minimal drop during cranking when it does work. What is the MOST likely cause of the 'click, no crank' symptom?General Electrical/Electronic System Diagnosis
  11. 61.A client complains that the vehicle's turn signals flash rapidly on one side, but the bulbs appear to be working correctly. A technician uses a scan tool to check for body control module (BCM) fault codes but finds none. Which of the following is the MOST likely cause of this condition?General Electrical/Electronic System Diagnosis
  12. 62.A vehicle's left turn signal flashes rapidly, but the right turn signal operates normally. All other lights function correctly. What is the most probable cause?Lighting Systems Diagnosis and Repair
  13. 63.A vehicle exhibits intermittent flickering of the instrument cluster lights. A technician suspects a poor ground connection. Which of the following is the MOST effective diagnostic tool to confirm a poor ground for the instrument cluster?General Electrical/Electronic System Diagnosis
  14. 64.A technician is diagnosing a vehicle with an intermittent no-start condition. The technician determines that the fuel pump is not operating. Using a wiring diagram, the technician identifies the fuel pump relay. When the ignition is turned to the 'ON' position, the technician hears the relay click, but the fuel pump does not run. What should the technician check NEXT?General Electrical/Electronic System Diagnosis
  15. 65.A technician is diagnosing a vehicle with an intermittent 'Check Engine' light and a stored DTC P0301 (Cylinder 1 Misfire). Using an oscilloscope, the technician connects to the ignition coil primary circuit for cylinder 1 and observes a waveform that shows a normal firing line, but a very short spark duration (less than 0.5ms) compared to specifications (1.0ms - 1.5ms). All other cylinders show normal spark duration. What is the most likely cause of this misfire?General Electrical/Electronic System Diagnosis
  16. 66.A technician is diagnosing a vehicle with an intermittent 'Check Engine' light and a stored DTC P0420 (Catalyst System Efficiency Below Threshold Bank 1). The technician monitors live data and observes the upstream oxygen sensor (O2S11) switching rapidly between 0.1V and 0.9V, while the downstream oxygen sensor (O2S12) is also switching, but more slowly, between 0.3V and 0.7V. What does this data indicate about the catalytic converter?General Electrical/Electronic System Diagnosis
  17. 67.A vehicle with a 'smart charge' system has an intermittently illuminated battery light and fluctuating charging voltage. A scan tool reveals a Diagnostic Trouble Code (DTC) for the Battery Current Sensor (BCS) circuit. What is the MOST likely impact of a faulty BCS on the charging system?Charging System Diagnosis and Repair
  18. 68.A technician is diagnosing a vehicle where the horn does not work. The fuse for the horn circuit is good, and the horn relay clicks when the horn button is pressed. Using a digital multimeter, the technician measures 12.5V at the output terminal of the horn relay when the horn button is pressed, but the horn itself does not sound. Which of the following is the MOST likely cause of the inoperative horn?General Electrical/Electronic System Diagnosis
  19. 69.A technician is diagnosing a no-charge condition on a vehicle. With the engine running, a voltmeter connected from the alternator's B+ terminal to ground reads 14.2V. However, the battery voltage simultaneously reads 12.5V. What is the MOST probable cause?Charging System Diagnosis and Repair
  20. 70.A technician is troubleshooting a vehicle where the rear defroster does not activate. Using a wiring diagram, the technician identifies the defroster relay. With the ignition on, the technician checks for voltage at the relay's coil power supply terminal (Pin 86) and finds 12.0V. The technician then checks the ground-side control terminal (Pin 85) and observes 0V when the defroster switch is activated. What do these readings indicate?General Electrical/Electronic System Diagnosis
  21. 71.A technician is diagnosing an intermittent issue where a vehicle's power windows occasionally stop working. The technician observes that the windows sometimes work perfectly, and other times they are completely inoperative. When inoperative, neither the master switch nor individual door switches can operate the windows. All fuses are good. What is the MOST likely cause?General Electrical/Electronic System Diagnosis
  22. 72.A technician is performing a parasitic drain test. With the ignition off and all doors closed, the ammeter connected in series with the battery's negative terminal shows a 500 mA draw. What is the next logical step in diagnosing this excessive drain?General Electrical/Electronic System Diagnosis
  23. 73.A client complains that their vehicle's interior dome light does not turn on when any door is opened, but it works correctly when manually switched on. A technician tests the door jamb switches and finds they all show continuity to ground when the door is open. The fuse for the dome light is good, and the bulb is confirmed working. What is the MOST probable cause?General Electrical/Electronic System Diagnosis
  24. 74.A client complains that their vehicle's dashboard lights occasionally flicker or dim while driving, especially over bumps. The technician performs a voltage drop test on the main power feed to the instrument cluster and finds 0.8 volts of drop when the lights are actively flickering. What is the most appropriate next step in diagnosing this issue?General Electrical/Electronic System Diagnosis
  25. 75.A technician is diagnosing a vehicle that intermittently fails to start. When the ignition key is turned to the 'START' position, the technician observes that the starter motor does not engage, and there is no click from the starter solenoid. Further testing reveals that the battery voltage is 12.6V, and the voltage at the starter solenoid's S-terminal (control wire) is 12.0V when the key is in the 'START' position. What is the MOST likely cause of this condition?General Electrical/Electronic System Diagnosis
  26. 76.A customer complains that their vehicle's headlights dim significantly at idle and the battery warning light flickers, but the problem seems to go away at highway speeds. The battery tests good. What is the MOST likely cause?Charging System Diagnosis and Repair
  27. 77.A client complains that their vehicle's dashboard turn signal indicator lights illuminate but do not flash, and the exterior turn signals also do not flash. All other lights on the vehicle are operating correctly. Which of the following is the MOST likely cause?Lighting Systems Diagnosis and Repair
  28. 78.A technician is diagnosing a charging system issue where the battery light is always on, but the system appears to be charging correctly at 14.2V. A check of the 'L' (lamp) terminal circuit reveals that it is not being pulled to ground by the alternator's internal regulator when the engine is running. What is the most likely cause?Charging System Diagnosis and Repair
  29. 79.A technician is diagnosing a complaint of dim headlights on a vehicle. The battery voltage measures 12.6V with the engine off. When the headlights are turned on, the voltage at the headlight bulb connector measures 10.5V. Which of the following is the most likely cause?Lighting Systems Diagnosis and Repair
  30. 80.A vehicle owner reports that their high-beam headlights work correctly, but the low-beam headlights do not illuminate on either side. All other exterior lights are functioning normally. The vehicle uses a dual-filament H4 type bulb for the headlights. What is the MOST likely cause?Lighting Systems Diagnosis and Repair
  31. 81.A vehicle's charging system is being diagnosed. The technician notes that the voltage at the battery is 12.3V with the engine off. With the engine running at 2000 RPM, the voltage at the battery increases to 14.5V. However, when the headlights, blower motor, and rear defroster are all turned on, the voltage drops to 13.0V and the battery light flickers. The alternator is rated for 150 Amps. A quick check of the alternator drive belt shows no signs of slippage or wear. What is the most likely cause?Charging System Diagnosis and Repair
  32. 82.A technician is inspecting a wiring harness that has been damaged by rodent activity, resulting in several exposed copper strands. The damage is localized to a small section of a non-critical sensor circuit. Which of the following is the MOST appropriate repair method for this type of damage?General Electrical/Electronic System Diagnosis
  33. 83.A technician is diagnosing a vehicle with an intermittent 'no crank' condition. When the ignition key is turned to the 'START' position, the technician observes that the starter motor does not engage, but a distinct 'click' is heard from the starter solenoid. Further testing reveals that battery voltage is 12.5V, and the voltage at the starter motor's large battery cable terminal (B+ terminal) is 12.4V. What is the MOST likely cause of this condition?General Electrical/Electronic System Diagnosis
  34. 84.A vehicle owner reports that their battery light illuminates intermittently, especially at idle or low engine RPMs. A technician measures the charging voltage at the battery, which consistently reads 13.2 volts with the engine running at 2000 RPM. What is the most likely cause?Charging System Diagnosis and Repair
  35. 85.A technician is diagnosing a vehicle with an intermittent 'Check Engine' light and a stored DTC for 'MAP Sensor Circuit Low Input'. Using a scan tool, the technician observes the Manifold Absolute Pressure (MAP) sensor reading. With the engine off (KOEO), the MAP sensor reads 1.5V. When the engine is started and idling, the MAP sensor reads 0.9V. The atmospheric pressure at the technician's shop is 14.7 psi (101 kPa, 29.92 inHg). What do these readings MOST likely indicate?General Electrical/Electronic System Diagnosis
  36. 86.A technician is diagnosing an intermittent short to ground in a vehicle's tail light circuit. The fuse blows only when the vehicle goes over bumps. Which of the following wiring repair techniques is LEAST likely to resolve this specific issue permanently?General Electrical/Electronic System Diagnosis
  37. 87.A technician is diagnosing a vehicle with an intermittent issue where the rear defroster does not activate. The technician uses a scan tool and observes that the Body Control Module (BCM) reports the defroster switch input as 'ON' when the button is pressed, but the defroster relay output status remains 'OFF'. The BCM also shows no fault codes related to the defroster circuit. What is the most likely cause of the defroster not activating?General Electrical/Electronic System Diagnosis
  38. 88.A technician is performing a diagnostic on a vehicle where the left front headlight is dim, but the right front headlight is bright. A voltage drop test is conducted on the power side of the left headlight circuit, measuring from the positive battery post to the headlight bulb's positive terminal, showing 2.5V. The ground side voltage drop for the left headlight measures 0.1V. What does this indicate?Lighting Systems Diagnosis and Repair
  39. 89.A vehicle's high-beam headlights function, but the low-beam headlights do not. When the headlight switch is in the low-beam position, a test light connected to the low-beam wire at the headlight connector illuminates brightly. The ground connection for the headlights is verified to be good. What is the most likely cause?Lighting Systems Diagnosis and Repair
  40. 90.A technician is diagnosing a vehicle with an intermittent 'Check Engine' light and a stored P0301 (Cylinder 1 Misfire Detected) diagnostic trouble code. The technician uses an oscilloscope to capture the secondary ignition waveform of cylinder 1. The waveform shows a short spark duration and a low peak firing voltage. All other cylinders show normal waveforms. What is the MOST likely cause of this abnormal waveform?General Electrical/Electronic System Diagnosis
  41. 91.A technician is using service information to troubleshoot an intermittent fault with a vehicle's anti-lock braking system (ABS). The wiring diagram shows a wire labeled 'C140-12A-GN/RD'. What does the 'GN/RD' designation most likely represent?General Electrical/Electronic System Diagnosis
  42. 92.A technician is diagnosing a vehicle with an intermittent no-start condition. The technician suspects a faulty ignition relay. Using a digital multimeter, the technician performs the following tests: 1) Verifies 12V at terminal 30 (power input) of the relay socket. 2) Verifies 12V at terminal 85 (coil ground control) when the key is in the 'start' position. 3) Verifies a good ground at terminal 86 (coil power input). Which of the following is the MOST appropriate next step in the diagnosis?General Electrical/Electronic System Diagnosis
  43. 93.A vehicle's daytime running lights (DRLs) are inoperative, but the high beams, low beams, and parking lights all function correctly. The DRL module is integrated into the vehicle's Body Control Module (BCM). A scan tool shows no diagnostic trouble codes (DTCs) related to the DRL system. When the DRLs should be on, a voltage reading at the DRL bulb socket shows 0V. What is the MOST likely cause?Lighting Systems Diagnosis and Repair
  44. 94.A technician is performing a parasitic drain test on a vehicle that has a dead battery overnight. After connecting an ammeter in series with the battery negative terminal, the initial draw is 3.5 amps. After waiting for 15 minutes, the draw drops to 0.8 amps, which is still too high. What is the most appropriate next step to locate the source of the excessive drain?General Electrical/Electronic System Diagnosis
  45. 95.A technician is diagnosing a vehicle with an intermittent no-start condition. The technician determines that the fuel pump is not receiving power. Using a multimeter, the technician measures 12 volts at the fuel pump relay's coil input, but 0 volts at the relay's switched output when the engine is cranked. Which of the following is the MOST likely cause?General Electrical/Electronic System Diagnosis
  46. 96.A technician is diagnosing a vehicle with an intermittently illuminated battery light and occasional low voltage readings. The vehicle uses a smart charging system controlled by the Powertrain Control Module (PCM). A scan tool reveals no diagnostic trouble codes (DTCs). Live data shows the 'Desired Charge Voltage' fluctuates rapidly, but the 'Actual Charge Voltage' remains consistently lower. Which of the following is the most likely cause?Charging System Diagnosis and Repair
  47. 97.A vehicle's battery light comes on while driving and stays on. The technician performs a battery test, which passes. The charging voltage at the battery is 12.6V with the engine running. An alternator output test shows the alternator is producing 80 amps under load, but its rated output is 140 amps. Which of the following is the most likely cause?Charging System Diagnosis and Repair
  48. 98.A client complains that their vehicle's dashboard lights occasionally flicker or dim while driving, especially when activating other electrical accessories like power windows or the air conditioning. The technician performs a voltage drop test across the main power feed cable from the battery to the fuse box and observes a reading of 0.8V with several accessories activated. What is the MOST appropriate next step for the technician?General Electrical/Electronic System Diagnosis
  49. 99.A technician is using service information to troubleshoot an intermittent issue with a vehicle's horn. The wiring diagram shows a 'C103' designation next to a connector. What does 'C103' most likely represent?General Electrical/Electronic System Diagnosis
  50. 100.A vehicle's charging system warning light is illuminated, and the voltmeter shows 12.0V with the engine running. A visual inspection reveals a severely corroded battery positive terminal. After cleaning the terminal, the warning light remains on, and voltage is still 12.0V. What is the most likely issue now?Charging System Diagnosis and Repair