Automotive Electrical and Electronic Systems
Core concepts
Understand basic electrical theory: voltage, current, resistance and Ohm's law, plus series and parallel circuits. Know battery construction, testing and charging, starting and charging systems, and the operation of relays, fuses and switches. Understand wiring diagrams, connector repair, voltage drop testing and the difference between a short to ground and an open circuit. Cover sensors and actuators, engine control units, CAN bus networks and the effect of high resistance on signal circuits. Know safe practices for high-voltage hybrid and electric vehicles, including isolation and PPE.
Traps
Questions often test whether a test light or a multimeter is appropriate, and whether voltage should be measured with the circuit loaded. Watch for confusion between voltage drop and resistance, and for the assumption that a blown fuse is always the root cause rather than a symptom. Another trap is probing connectors carelessly and damaging terminals.
Worked example
A starter cranks slowly. Measure battery voltage at rest and during cranking. Then perform a voltage drop test from the battery positive to the starter terminal while cranking. A drop greater than about 0.5 volts indicates excessive resistance in the cable or connections, which should be repaired before condemning the starter.
Rule of thumb
Test under load. A circuit that reads correct voltage unloaded can still fail when current flows.