General Electrical/Electronic Diagnosis
26%of exam
Ohm's LawVoltage DropDMM TestingCAN BusCircuit Protection
Battery & Starting
18%of exam
OCV ReadingsLoad TestAGM vs FloodedStarter DrawVoltage Drop
Charging System
10%of exam
Alternator OutputAC RippleVoltage RegulationSmart Charging
Lighting Systems
12%of exam
HID vs LEDHyperflash FixAdaptive HeadlightsDRL Method
Body Electrical Systems
34%of exam
HMI ClusterComfort AccessoriesSRS SafetySecurity SystemsHeated Accessories
Quick Facts
- Exam
- ASE A6
- Credential
- Electrical/Electronic Systems
- Questions
- 60 total / 50 scored
- Time
- 90 minutes
- Pass
- Scaled score, ~70% guide
- Format
- Computer-based, Prometric
- Level
- Master tech required
- Blueprint
- 2026 ASE Study Guide
Ohm's Law Triangle
V over I times R
V = I x RI = V / RR = V / I
Fuse vs Fusible Link
Fuse
- One-time sacrificial device
- Opens at fixed rating
Fusible Link
- Smaller-gauge wire section
- Must match original spec
Device vs wire
Test Tool Picker
- Need volts, ohms, amps→DMM
- Need signal over time→Oscilloscope
- Need current, no break→Amp clamp
- Circuit stays energized, loaded→Voltage drop test
- Circuit must be de-energized→Resistance or continuity test
- Need scan data or DTCs→Scan tool
Electrical Fundamentals
- Ohm's Law
- V = I x R
- Watt's Law
- P = V x I
- Series circuit
- One current path, voltage divides
- Parallel circuit
- Multiple paths, equal voltage each
- Open circuit
- Broken path, no current flows
- Short circuit
- Unwanted low-resistance path forms
- Ground
- Circuit's return path to battery
Voltage Drop Thresholds
0.1V connector, 0.2V starter cable
Connector: 0.1V maxStarter cable: 0.2V maxGround point: 0.1V max
Series vs Parallel Circuits
Series
- One current path
- Voltage divides across loads
Parallel
- Multiple current paths
- Same voltage each branch
Current same vs voltage same
DMM & Test Equipment
- DMM
- Measures volts, ohms, amps
- Voltage drop test
- Circuit energized and under load
- Max drop per connector
- 0.1V per connection point
- Starter cable max drop
- 0.2V on positive cable
- Parasitic draw normal
- 20-50 mA key-off
- Ohmmeter rule
- Test only de-energized circuits
- Oscilloscope use
- View signal changes over time
- Amp clamp
- Reads current without breaking circuit
CAN Bus Voltage States
Recessive 2.5V both, dominant splits apart
Recessive: both near 2.5VDominant: CAN-H up, CAN-L down
CAN Bus vs LIN Bus
CAN
- Two wires, high speed
- Powertrain, safety-critical systems
LIN
- Single wire, low speed
- Non-critical body functions
Critical vs convenience
Networks & Circuit Protection
- CAN bus
- Two-wire, high-speed module network
- CAN idle voltage
- Both lines near 2.5V
- CAN bus resistance
- 60 ohms, two terminators parallel
- LIN bus
- Single-wire, low-speed body network
- Gateway module
- Translates between bus protocols
- Bus-off condition
- Module disabled its own transmitter
- Fuse
- One-time sacrificial overcurrent device
- Circuit breaker
- Resettable overcurrent protection device
- Fusible link
- Replace with identical link only
- Wiring diagram dot
- Solid dot means spliced connection
Voltage Drop vs Resistance Test
Voltage Drop
- Circuit energized
- Under normal load current
Resistance Test
- Circuit de-energized
- Meter supplies test current
Powered vs unpowered
Battery State of Charge
12.6 full, 12.4 75%, 12.2 half
12.6V: 100%12.4V: 75%12.2V: 50%12.0V: 25% or less
AGM vs Flooded Battery
AGM
- Absorbed glass mat
- Sealed, deep-cycle tolerant
Flooded
- Free liquid electrolyte
- Needs maintenance and venting
Stop-start vs standard
Starting Fault Picker
- Rapid solenoid clicking→Load test the battery
- Slow or no crank→Voltage drop test cables
- Won't crank in gear→Check neutral safety switch
- High starter current draw→Suspect dragging starter
- Battery good, still no start→Test starter circuit drop
Battery Types & Testing
- Full charge OCV
- About 12.6 volts resting
- 50% charge OCV
- About 12.2 volts resting
- AGM battery
- Sealed, absorbed glass mat electrolyte
- EFB battery
- Enhanced flooded, entry-level stop-start
- Load test spec
- Half CCA, 15 seconds, 9.6V+
- Conductance test
- AC signal measures internal resistance
- Battery state of charge
- Each 0.2V step is 25%
Load Test vs Conductance Test
Load Test
- Applies heavy DC load
- Reads voltage sag directly
Conductance Test
- Sends small AC signal
- Estimates internal resistance value
Direct load vs signal
Starting System Diagnosis
- Starter draw, 4-cyl
- Roughly 50-100 amps
- Starter draw, 8-cyl
- Roughly 100-200 amps
- Starter cable voltage drop
- Max 0.2V during cranking
- Rapid solenoid click
- Weak battery or high resistance
- Neutral safety switch
- Blocks crank outside Park/Neutral
- Slow crank cause
- Battery, cables, or starter drag
- No crank cause
- Open circuit or dead battery
Charging Fault Picker
- Voltage below 13.5V→Suspect undercharge
- Voltage above 14.5-15V→Suspect overcharge
- Ripple above 500 mV→Suspect failed diodes
- Lamp on, engine running→Check belt, circuit, alternator
- Output weak under load→Test alternator output
Charging System Diagnosis
- Normal charging voltage
- 13.5 to 14.5 volts
- Undercharging sign
- Below 13.5V, weak output
- Overcharging sign
- Above 14.5-15V, bad regulator
- AC ripple normal
- Under 100-200 mV
- AC ripple failure
- Above 500 mV, bad diodes
- Charge lamp stays lit
- Belt, circuit, or alternator fault
- Smart charging
- PCM commands variable alternator output
- Output test spec
- 90% rating near 2000 RPM
HID vs LED Headlights
HID
- Gas discharge, needs ballast
- Fades or shifts blue
LED
- Solid-state diode source
- Draws far less current
Ballast vs diode
Lighting Systems & Components
- HID dimming/blue shift
- Aging or failing HID bulb
- LED hyperflash cause
- Flasher reads low LED current
- Hyperflash fix
- Load resistors or LED flasher
- DRL method
- Reduced voltage or PWM headlights
- Adaptive headlight inputs
- Steering angle plus vehicle speed
- Multiple lights fail together
- Suspect shared fuse or ground
- Trailer brake control
- Dedicated relays and control module
Body Electrical Fault Picker
- Fault follows one component→Isolate that component first
- Fault spans several circuits→Suspect shared fuse or ground
- SRS lamp lit→Scan for stored codes
- Camera shows no image→Check power, ground, signal
- Immobilizer blocks starting→Check transponder code match
HMI & Instrument Cluster
- Multiplexed cluster data
- Arrives over CAN or LIN
- Stepper motor gauge
- Digital, precise needle positioning
- Air-core gauge
- Older analog crossed-coil design
- Fuel gauge false reading
- Sender or ground circuit fault
- HMI systems
- Cluster, info display, infotainment
Comfort & Convenience Accessories
- Power window slow both ways
- Shared power or ground fault
- Memory seat function
- Position sensors report to module
- One door lock fails
- Isolate to that door's actuator
- Blower runs high only
- Resistor block or PWM module
- Heated seat no warmth
- Check element continuity, thermostat
- Defroster grid break
- Voltage drop test finds it
Security, SRS & Safety Systems
- Transponder immobilizer
- Chip code must match module
- Weak keyless entry range
- Fob battery is weakening
- Anti-theft blocks crank
- Module failed to disarm
- SRS lamp stays on
- Fault stored, airbags disabled
- Clock spring
- Coiled cable feeds steering wheel
- Before SRS service
- Disconnect battery, wait per spec
- Wiper won't park
- Check park switch circuit first
- Backup camera no image
- Check power, ground, signal path
Common Traps
Voltage Drop ≠ Resistance Test
Drop test: circuit energized ≠ Resistance test: circuit de-energized
Fuse ≠ Fusible Link
Fuse: one-time sacrificial device ≠ Fusible link: harness wire section
AGM ≠ Standard Flooded Battery
AGM: sealed, deep-cycle ready ≠ Flooded: free liquid, maintainable
CAN Bus ≠ LIN Bus
CAN: two wires, fast ≠ LIN: one wire, slow
Load Test ≠ Conductance Test
Load test: heavy DC draw ≠ Conductance test: small AC signal
HID Fade ≠ LED Hyperflash
HID: bulb ages, dims and blues ≠ LED: flasher misreads low current
Last Minute
- 1.Domain weights: 26-18-10-12-34%
- 2.60 total, 50 scored questions
- 3.90 minutes, computer-based test
- 4.Passing score is scaled, not fixed
- 5.Ohm's Law: V = I x R
- 6.Voltage drop needs energized circuit
- 7.Resistance test needs de-energized circuit
- 8.Max connector drop: 0.1 volts
- 9.Max starter cable drop: 0.2 volts
- 10.AGM seals; flooded needs maintenance
- 11.CAN bus: two wires, high-speed
- 12.Body Electrical: 34%, largest area
- 13.Retake wait: 30 full days
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