ASE4 Engine Electrical Systems 2 — Questions and Answers
Question 1: A parasitic draw test finds 350 mA of current drain with the vehicle in sleep mode. Maximum acceptable is typically:
- 500 mA
- 50 mA
- 200 mA
- 100 mA or less (Correct answer)
Correct answer: 100 mA or less
Acceptable parasitic draw is generally 50 mA or less for most vehicles; some manufacturers allow up to 100 mA, making 350 mA significantly excessive.
Question 2: To isolate a parasitic draw to a specific circuit, the technician should:
- Disconnect the battery and check individual fuses with a test light in series (Correct answer)
- Remove and reinstall the battery repeatedly
- Use a voltmeter across the battery terminals with the car off
- Start the engine and check for AC ripple on the alternator
Correct answer: Disconnect the battery and check individual fuses with a test light in series
Placing a test light or ammeter in series with each fuse while monitoring current change allows the technician to isolate the draw to a specific circuit.
Question 3: A CAN (Controller Area Network) bus fault can cause:
- Only the engine to fail to start
- Multiple unrelated DTCs across various modules simultaneously (Correct answer)
- Only fuel injector faults to appear
- Just an inoperative radio
Correct answer: Multiple unrelated DTCs across various modules simultaneously
Since many modules communicate over the CAN bus, a bus fault can produce numerous DTCs across multiple unrelated systems at once.
Question 4: An alternator with an open diode will produce:
- Zero charging output
- Reduced output and AC ripple on the charging circuit (Correct answer)
- Overcharging above 15 volts
- Normal output with no noticeable effect
Correct answer: Reduced output and AC ripple on the charging circuit
An open diode reduces alternator output by preventing conversion of part of the AC waveform to DC, and causes measurable AC ripple.
Question 5: Battery sulfation typically occurs when a battery is:
- Overcharged repeatedly
- Left discharged for extended periods (Correct answer)
- Charged too quickly with a fast charger
- Exposed to temperatures below freezing
Correct answer: Left discharged for extended periods
Sulfation occurs when lead sulfate crystals harden on the battery plates during prolonged discharge, reducing the battery's capacity permanently.
Question 6: A technician uses an inductive ammeter clamp on the negative battery cable and reads 1.8 amps with the car in sleep mode. The FIRST thing to verify is:
- Whether the alternator has a bad diode
- That all modules have fully entered sleep mode (wait 20–30 minutes after key-off) (Correct answer)
- That the battery is fully charged
- That the test light method is used instead
Correct answer: That all modules have fully entered sleep mode (wait 20–30 minutes after key-off)
Many modules remain active for several minutes after key-off; a high reading shortly after shutdown may simply indicate normal module sleep transition.
ASE4 Engine Electrical Systems 2
A parasitic draw test finds 350 mA of current drain with the vehicle in sleep mode.
Maximum acceptable is typically: