Automotive Service Excellence (ASE) A6 Electrical/Electronic Systems flashcards

A procedure to measure the amount of current drawn from the battery when the vehicle's ignition is off and all systems are in their 'sleep' state, used to identify excessive battery drain.

• Measured in series with the battery.
• Vehicle must be 'asleep'.
• Acceptable draw typically 20-50 mA.

Memory trick: To find the battery ghost, pull fuses one by one, watching the current meter.

A wiring repair method that ensures long-term electrical integrity, mechanical strength, and environmental protection, often involving proper crimping, soldering (where appropriate), heat-shrink sealing, and proper routing.

• Durable and robust.
• Resistant to vibration and moisture.
• Matches or exceeds OEM standards.

Memory trick: Don't just patch, make it last; a permanent fix beats a quick blast.

A circuit design where a constant voltage is supplied to a component, and a switch or control module completes the circuit by providing a ground path.

• Component always has power
• Switch/module provides ground to activate
• Common in lighting and relay circuits

Memory trick: Manual works, door fails; ground path prevails.

A systematic approach to identifying faults in an electrical circuit, typically involving checks of power, ground, and component integrity.

• Always check both power and ground paths.
• Voltage drop tests identify resistance under load.
• Intermittent issues often point to loose connections or wiring.

Memory trick: Follow the path: Power, Ground, Component.

A starter solenoid can fail internally, preventing the starter motor from engaging, even when it receives the correct control voltage from the ignition switch.

• Commonly caused by worn or pitted internal contacts.
• Symptoms include no starter motor engagement and no solenoid click.
• Requires solenoid or starter motor replacement.

Memory trick: Key turns, power flows, but the solenoid's silent show.

The flasher relay is an electrical component in a vehicle's turn signal and hazard light circuits responsible for intermittently interrupting the current to cause the lights to flash.

• Creates the on-off blinking action for turn signals and hazard lights.
• Can be thermal, electromechanical, or electronic.
• Failure often results in no flashing (lights stay on or off) or incorrect flash rate.

Memory trick: No Flash? Check the Flasher!

The battery warning light (L terminal) circuit is typically designed to illuminate when there is a voltage difference across the light bulb (ignition voltage on one side, ground from the regulator on the other), and turn off when the alternator output voltage matches ignition voltage, effectively removing the ground.

• Provides initial field excitation.
• Regulator controls its ground path.
• Stays on if regulator fails to remove ground when charging.

Memory trick: Light on, charge fine? Regulator's line is out of sync design.

Dual-filament bulbs contain two separate filaments for different lighting functions (e.g., high/low beam, park/turn). One filament can fail while the other continues to operate, leading to partial lighting functionality.

• Common in older headlights (H4) and combination park/turn signals (1157).
• Failure of one filament does not necessarily affect the other.
• Diagnosis involves checking continuity of each filament and voltage at socket.

Memory trick: One filament down, the other still shines around!

An alternator may be considered undersized if it cannot meet the vehicle's total electrical current demands, especially under heavy load (all accessories on). Symptoms include voltage drop and battery light flickering under load, despite appearing to charge normally under light load.

• Alternator rated output must exceed maximum vehicle load.
• Symptoms appear only under heavy electrical load.
• Voltage drops significantly, battery light may flicker.

Memory trick: Big load, tiny gen, voltage low, start again.

A method of permanently joining electrical wires by melting solder over the twisted or crimped wires, then insulating with heat-shrink tubing.

• Provides a strong, low-resistance electrical connection.
• Requires proper technique to avoid cold solder joints.
• Always insulated with heat-shrink tubing for protection.

Memory trick: Solder and Shrink: A Lasting Fix for Rodent's Gnaw.

When a starter solenoid clicks but the starter motor does not crank, it typically indicates worn or pitted internal contacts within the solenoid, which prevents the high current flow to the starter motor windings, even though the solenoid plunger engages.

• Solenoid control circuit is working (it clicks).
• Main battery power is reaching the starter/solenoid.
• Internal solenoid failure to pass high current is the cause.

Memory trick: Click but no crank, solenoid's tired, a high-current tank.

Problems with the alternator's drive belt, such as wear, looseness, or glazing, can reduce the alternator's rotational speed, leading to insufficient power output, especially at lower engine RPMs.

• Causes intermittent or constant battery light.
• Leads to undercharging.
• Often accompanied by squealing noises.

Memory trick: If the belt is loose, the alternator is just cruising.

With the engine off (Key On, Engine Off - KOEO), a Manifold Absolute Pressure (MAP) sensor should output a voltage signal corresponding to atmospheric pressure. A significantly lower or incorrect reading at KOEO indicates a faulty MAP sensor.

• KOEO MAP voltage should reflect atmospheric pressure (e.g., 4.5-5.0V for 14.7 psi).
• Lower voltage indicates higher vacuum (or faulty sensor).
• Higher voltage indicates lower vacuum/higher pressure (or faulty sensor).

Memory trick: KOEO MAP, if it's low, the sensor's bad, it won't go.

Troubleshooting the low-current side of a relay circuit to ensure the control module is properly commanding the relay to activate.

• Relays have a control side (coil) and a power side (contacts).
• Control module commands the relay by powering/grounding the coil.
• Scan tool can often monitor switch inputs and relay output commands.
• If input is good but output command fails, check module or control wiring/relay coil.

Memory trick: INPUT makes BCM COMMAND the RELAY.

A high voltage drop on the power side of a circuit indicates excessive resistance in the path from the power source to the component, reducing the voltage available to operate the component.

• Measured between the power source (+) and the component's (+) terminal.
• Acceptable drop is typically <0.5V.
• Causes include corroded wires, loose connections, faulty switches/relays.

Memory trick: High drop on power, resistance is sour!

Confirming the presence of all necessary power and ground signals at a relay's input terminals to determine if the relay itself or its control circuit is faulty.

• Requires checking constant power, switched power/ground, and constant ground.
• If inputs are good but output is missing, suspect the relay.
• Often uses a multimeter or test light.

Memory trick: Inputs Good, Relay Next: Swap it Out, See the Start.

An internal fault within a Body Control Module (BCM) can cause specific output circuits to fail (e.g., DRLs, interior lights) even if other functions and inputs are working, and DTCs may not always be present.

• BCMs control many vehicle electrical functions.
• Internal component failure (e.g., transistor, driver) can affect single circuits.
• Lack of DTCs can make BCM diagnosis challenging; requires checking outputs directly.

Memory trick: BCM's quiet, DRLs riot!

A relay requires both control (coil) power and load (switched) power to operate correctly and deliver voltage to a component.

• Coil energization closes internal contacts.
• Switched power must be present for output voltage.
• Absence of switched power results in no output voltage.

Memory trick: Relays need two types of power to make things flow, coil to click, switched to glow.

Smart charging systems rely on various sensors (e.g., battery current, temperature, voltage) to provide data to the PCM, which then calculates the optimal 'Desired Charge Voltage'. Faulty sensor inputs can lead to incorrect charging strategies and system performance issues.

• PCM controls charging based on sensor inputs.
• Battery current sensor measures charge/discharge.
• Faulty sensor leads to inaccurate 'Desired Voltage'.

Memory trick: Desired's wild, actual's mild, sensor's child, system's riled.

Faults in the alternator's stator windings, such as opens or shorts, directly reduce the alternator's ability to generate its full rated alternating current, leading to undercharging and reduced maximum output.

• Stator windings generate AC before rectification.
• Shorts reduce effective turns, lowering output.
• Opens can cause complete loss of a phase, severely reducing output.

Memory trick: If the amps are low, the stator's flow might be slow.

Wiring diagrams use specific alphanumeric designations to identify connectors, helping technicians locate and test them in the vehicle.

• Commonly starts with 'C' for connector.
• Followed by a unique number.
• Often includes pin numbers for individual wires.

Memory trick: C marks the spot where wires connect, a number makes it perfect to detect.

A rapid flashing rate of a turn signal indicating a burnt-out bulb or reduced load in that circuit.

• Caused by reduced current draw due to a missing/burnt bulb.
• A diagnostic feature of turn signal flashers.
• Check all bulbs on the affected side.

Memory trick: Fast blink, bulb's brink!

Excessive resistance in the starter motor's ground path can prevent sufficient current flow, leading to 'click, no crank' symptoms.

• Ground circuit resistance should be very low (typically < 0.2V drop).
• High resistance restricts current, reducing motor torque.
• Often caused by corroded connections or loose cables.

Memory trick: Ground's High Drop Steals the Starter's Crank Power.

Electronic flasher relays, unlike thermal ones, can have more complex failure modes beyond simply not flashing. They might flash incorrectly, flash only one side, or provide steady power without flashing.

• Uses solid-state components, no moving parts.
• Often integrated into a BCM or dedicated module.
• Failure can manifest as hyper-flashing, no flashing, or steady illumination.

Memory trick: Steady light, flasher's plight!

A malfunction in the voltage regulator prevents the alternator from maintaining the correct charging voltage, leading to undercharging or overcharging.

• Regulates alternator output voltage.
• Internal or external component.
• Failure can cause battery undercharge/overcharge.

Memory trick: Regulate and Charge, or the Battery's in the Dark.

Positive fuel trim values (STFT, LTFT) indicate that the Powertrain Control Module (PCM) is adding fuel to the engine to correct a lean air-fuel mixture, as detected by the oxygen sensors.

• PCM adds fuel to compensate for excess oxygen in exhaust.
• Common causes include vacuum leaks, low fuel pressure, dirty injectors, unmetered air.
• Values above +/- 10% often indicate a problem.

Memory trick: Positive trim means fuel's a must, to fix the lean, we trust.

A fault in an electrical circuit where the connection is temporarily broken, often due to loose terminals, damaged wiring, or corroded connectors, causing intermittent component operation.

• Signal disappears completely
• Often related to movement or vibration
• Difficult to diagnose without dynamic testing

Memory trick: Wave's a ghost, where'd it go? Wiring's toast, or connection's slow.

Troubleshooting backup lights involves verifying power at the switch, then at the bulbs, and finally checking grounds and bulbs if power is present throughout the circuit.

• Typically activated by a switch on the transmission when in reverse.
• Power flows from fuse to switch, then to bulbs.
• Common issues include faulty switch, open wiring, or burnt bulbs.

Memory trick: Backup's dark? Power's lost its spark!

An engine sensor that monitors the rotational speed and position of the crankshaft, providing critical input to the engine control module (ECM) for fuel injection and ignition timing.

• Primary source of engine RPM signal.
• Essential for engine starting and running.
• Faulty sensor can cause no-start, stalling, or misfires.

Memory trick: Crankshaft Position is KEY to starting.

Using an oscilloscope to analyze the voltage and current patterns in the primary circuit of an ignition coil to diagnose ignition system faults.

• Firing line: voltage required to jump spark plug gap.
• Spark duration: time spark is maintained across the plug gap.
• Worn plugs or high resistance in secondary circuit shorten spark duration.
• Opens in primary or secondary circuits cause distinct waveform anomalies.

Memory trick: Waveform tells the spark's TALE.

The ability of a catalytic converter to reduce harmful emissions, assessed by comparing the activity of upstream and downstream oxygen sensors.

• Upstream O2 sensor should switch rapidly (0.1V-0.9V).
• Downstream O2 sensor should be relatively steady (around 0.6-0.7V) for a good converter.
• If downstream O2 sensor starts switching like upstream, converter efficiency is low (P0420).

Memory trick: Upstream WAVES, Downstream STAYS for good cats.

Alternators require an initial small current, known as excitation current, to flow through the rotor's field winding to create a magnetic field, which is necessary for the alternator to begin producing output voltage.

• Usually provided via the 'L' terminal or a dedicated excitation wire.
• Often routed through the battery light circuit.
• Without excitation, the alternator will not charge.

Memory trick: If the 'L' isn't lit, the field won't get its bit.

Troubleshooting circuits managed by a BCM involves verifying BCM input, BCM output, and wiring integrity to the load.

• BCM acts as an intelligent switch/relay.
• Check input signals to BCM (e.g., switch position).
• Check output signals from BCM to component.
• Wiring integrity between BCM and component is crucial.

Memory trick: BCM's path, wiring's wrath!

An electrical fault where a wire or circuit unintentionally comes into contact with a voltage source, causing an incorrect voltage reading or component operation.

• Often due to damaged insulation.
• Can be intermittent or constant.
• Causes unintended circuit activation or incorrect sensor readings.

Memory trick: Voltage where it shouldn't be, means a wire's touching, can't you see?

Normal voltage readings for a healthy 12V automotive battery and a properly functioning charging system.

• Fully charged 12V battery: ~12.6V (engine off).
• Normal charging voltage: 13.5V - 14.7V (engine running).
• Voltage outside these ranges indicates a potential issue.

Memory trick: 12.6 is FULL, 14.2 is CHARGING.

A momentary switch, typically located in the door frame, that completes or breaks a ground circuit to control interior lights or other functions when a door is opened or closed.

• Activates with door position.
• Often provides ground signal.
• Prone to intermittent failure.

Memory trick: Door switch: open, it grounds; closed, it's free. Test its ground-making ability.

The voltage output from a Manifold Absolute Pressure (MAP) sensor, which varies inversely with manifold vacuum/pressure and is used by the ECM to calculate engine load.

• Voltage changes with manifold pressure
• Should be stable at steady RPM/load
• Erratic signal causes fueling/timing issues

Memory trick: MAP's all jumpy, engine's grumpy.

A voltage drop test measures the resistance within a specific circuit segment by comparing voltage readings at different points, indicating how much voltage is 'lost' across that segment under load.

• Performed with a voltmeter across the component or wire.
• Lower voltage drop indicates lower resistance.
• Typically, <0.2V drop is acceptable for main power/ground cables.

Memory trick: If the voltage drops high on the cable, its resistance is a stable fable.

An ignition primary waveform exhibiting a lower peak voltage during coil turn-on and a shorter spark line duration suggests a short circuit in the secondary ignition system (spark plug, wire), preventing proper high voltage buildup and discharge.

• Lower primary peak voltage indicates less energy stored/released.
• Shorter spark line shows rapid discharge of secondary voltage.
• Often caused by carbon tracking, fouled spark plugs, or damaged plug wires.

Memory trick: Low peak, short spark, secondary short leaves its mark.

Measuring the voltage lost across a conductor or component in an accessory circuit while it is operating, indicating resistance in that part of the circuit.

• Acceptable voltage drop is typically 0.2V to 0.5V, depending on manufacturer and circuit type.
• Excessive voltage drop reduces the voltage available to the load, causing slow or inoperative function.
• Performed under load to accurately reflect circuit performance.

Memory trick: High drop on positive, means resistance is the culprit.

When a circuit has power to the component but the component does not operate, and it operates when a known good external ground is supplied, the fault lies in the component's original ground circuit, typically an open or high resistance.

• Component has power but doesn't work.
• Works when external ground is applied.
• Indicates original ground path is faulty.
• Common issues: loose connection, corrosion, broken wire.

Memory trick: Dome light has power, but needs a friend (ground) to shine. If it lights up with a new friend, the old one's gone.

Failure of an alternator's internal bearings leads to increased friction, whining or grinding noises, excessive heat, and eventually a seized pulley, preventing the alternator from rotating and producing output. This often results in a burning smell.

• Whining/grinding noises.
• Excessive heat in pulley/alternator housing.
• Difficult or impossible to turn by hand.
• Burning smell from friction/overheating.

Memory trick: Pulley's stuck, bearing's cooked, output's plucked, future looks crooked.

Using live data from upstream and downstream oxygen sensors to evaluate the effectiveness of the catalytic converter in reducing emissions.

• Upstream O2 sensor: Rapidly switches (0.1V-0.9V) reflecting air/fuel mixture control.
• Downstream O2 sensor: Should be slow and relatively flat/high voltage (0.7-0.9V) for an efficient converter.
• If downstream O2 sensor mirrors upstream or switches significantly, the converter is inefficient.

Memory trick: Upstream dances, downstream should snooze; if it moves too much, the cat's a dud.

The 'S' (sense) terminal on an alternator provides the voltage regulator with a direct feedback voltage from the battery or main power distribution, allowing the regulator to accurately monitor and maintain the vehicle's system voltage.

• Crucial for accurate voltage regulation.
• Often connected to battery positive or a main fuse box.
• An open circuit here can cause undercharging or no charging.

Memory trick: If 'S' has no volts, the regulator's sense jolts.

Electronic flasher relays monitor current draw to detect bulb failures. A reduced current (due to an open circuit like a blown bulb) can cause the remaining bulbs on that side to illuminate steadily or hyper-flash, and the dash indicator to behave similarly.

• Flasher relays detect current changes.
• Open circuit (blown bulb) reduces current.
• Steady illumination or hyper-flash indicates a bulb issue.
• Affects only the side with the fault, not both.

Memory trick: If the light is stuck 'on' and not blinking, it's probably missing its buddy bulb.

An excessive air gap between an inductive wheel speed sensor and its tone ring can cause intermittent signal drop-outs or erratic readings, especially at higher wheel speeds, due to a weakened magnetic field.

• Inductive sensors generate voltage from changing magnetic fields.
• Signal strength is inversely proportional to air gap.
• Damaged tone rings (missing teeth, warping) can also cause similar symptoms.

Memory trick: Wobbly signal, high speed's bane, air gap's wide, causing pain.

Worn carbon brushes in an alternator can lead to poor contact with the slip rings, reducing the field current and consequently the alternator's current output capacity.

• Brushes supply current to rotor.
• Wear reduces contact area.
• Results in low or intermittent current output.

Memory trick: Low Amps, High Suspects: Check Brushes and Wires.

The primary fuse or circuit breaker protects the entire headlight and taillight circuit from overcurrent, ensuring that a fault in one part does not disable the entire electrical system.

• Often a single fuse protects both headlights and taillights.
• Failure leads to complete loss of these lights.
• Other circuits remain operational if their fuses are separate.

Memory trick: Lights out, but everything else is bright, check the big light fuse first, not the dimmer switch.

An oscilloscope displays electrical signals as waveforms over time, making it invaluable for capturing and analyzing intermittent electrical faults, such as momentary open circuits or signal dropouts.

• Displays voltage over time.
• Can capture transient events.
• Useful for identifying glitches and dropouts.

Memory trick: Intermittent opens are ghost faults; only an oscilloscope can see their fleeting presence.

The rectifier assembly within an alternator converts the alternating current (AC) produced by the stator windings into direct current (DC) required by the vehicle's electrical system and battery.

• Consists of multiple diodes (usually 6 or 8).
• Essential for converting AC to DC power.
• Failure leads to no or low charging output.

Memory trick: Rectifiers are the AC/DC bridge, if they fail, the power won't flow.

Diagnosing an excessive parasitic draw involves measuring the current draw with the vehicle off and then systematically isolating the faulty circuit by pulling fuses until the current draw returns to an acceptable level (typically 20-50 mA).

• Excessive draw drains battery overnight.
• Acceptable draw: 20-50 mA (varies by vehicle).
• Fuse pulling isolates the faulty circuit.

Memory trick: Draw is high, battery dies, pull the fuse, find the lies.

A fault in the multi-function switch (turn signal switch) can prevent power from reaching specific lighting circuits, leading to a complete failure of lights on one side or particular functions.

• Controls turn signals, sometimes wipers, high beams, and cruise control.
• Internal contacts can wear or corrode, preventing current flow.
• Failure affects functions routed through that specific part of the switch.

Memory trick: One side out? Switch it about!

Hall-effect sensors are digital sensors that produce a clean square wave output, switching between a high and low voltage state as a trigger wheel passes, signaling position or speed.

• Digital output.
• Produces square wave.
• Voltage switches abruptly.

Memory trick: Hall effect: a square dance of ON and OFF states.

When the alternator cannot supply enough current to meet the vehicle's electrical demands, leading to voltage drops and flickering lights.

• Occurs with engine running and electrical loads on.
• Indicates a weak alternator, loose belt, or poor connections.
• Can be diagnosed by measuring charging voltage under load.

Memory trick: Load's a pain, alternator's stain!

The 'L' (Lamp) terminal on an alternator typically provides a ground signal to illuminate the battery warning light when the alternator is not charging or is undercharging. When charging correctly, this terminal is usually pulled high or open, turning the light off.

• L-terminal: Lamp control.
• Low signal (ground) = light on (no charge).
• High/open signal = light off (charging).

Memory trick: L is low, light will glow, charge is slow, or no show.

A diagnostic test performed with the circuit operating under its normal electrical load, measuring the difference in voltage between two points to identify excessive resistance.

• Performed under load.
• Measures unwanted resistance.
• Identifies circuit section with high resistance.

Memory trick: Dim lights mean voltage is shy; find its hiding spot with a drop test.

A door jamb switch typically completes a ground circuit to activate interior lights when a door is opened. Testing its resistance to ground with the door open can confirm its functionality.

• Commonly provides a ground signal.
• Low resistance to ground (near 0Ω) indicates a closed switch and good ground.
• High resistance or open indicates a faulty switch or wiring.

Memory trick: Door open, light off: check ground switch, or you're lost.

A dimmer switch (rheostat or electronic) controls the intensity of interior illumination. Failure can result in complete loss of power to the controlled lights or inability to adjust brightness.

• Typically controls instrument panel, radio, and HVAC panel illumination.
• Can be a variable resistor (rheostat) or electronic module.
• Failure often leads to all controlled lights being off or stuck at one brightness.

Memory trick: Dash dark? Dimmer's mark!

A switch, typically located in the door frame, that detects if a door is open or closed, often controlling interior lights or door ajar warnings.

• Usually a normally closed switch that opens when the door closes.
• Provides a ground or signal to the body control module (BCM).
• A stuck switch can lead to lights staying on or not turning on.

Memory trick: The dome light's always on, like a never-ending party, because a door switch is stuck in 'open' mode.

Component Location Diagrams within service information provide visual and textual guidance for the physical location of electrical components, sensors, and multi-pin connectors on a vehicle.

• Essential for physically locating components identified on wiring diagrams.
• Often include illustrations, photos, and descriptions.
• May be part of 'Electrical' or 'Body' sections of service manual.

Memory trick: Need to find a plug? Component diagrams give a hug.