Electrical Systems & Emissions Control Flashcards
7 cards from real NAPA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems & Emissions Control flashcards as text
What type of signal does a Hall-effect crankshaft position sensor produce?
Answer: A digital square wave
Hall-effect sensors switch on and off, producing a digital square-wave signal with constant amplitude.
How does the output of a magnetic (variable reluctance) crank sensor change as engine speed increases?
Answer: AC voltage amplitude and frequency both increase
A magnetic pickup generates its own AC voltage, which grows in amplitude and frequency as the reluctor spins faster.
How does the resistance of a typical engine coolant temperature (NTC thermistor) sensor change as the engine warms up?
Answer: Resistance decreases
A negative temperature coefficient thermistor loses resistance as temperature rises.
What reference voltage does the PCM typically supply to a throttle position sensor?
Answer: 5 volts
Most three-wire sensors such as the TPS receive a regulated 5 V reference from the PCM.
What does a hot-wire mass airflow sensor actually measure?
Answer: The mass of air entering the engine
The sensor measures the current needed to keep a heated element at temperature, which corresponds to air mass.
How does the PCM on an OBD II vehicle typically detect an engine misfire?
Answer: By monitoring crankshaft speed fluctuations
A misfiring cylinder causes the crankshaft to slow briefly, which the PCM sees through the crank position sensor.
What is a typical primary winding resistance specification for an ignition coil?
Answer: 0.4 to 2 ohms
The primary winding uses few turns of heavy wire, so its resistance is very low compared to the secondary.