Automotive Electrical and Electronic Systems
Electrical fundamentals
Understand Ohm’s law, series and parallel circuits, voltage drop, resistance and current flow. Know battery construction and testing, charging and starting systems, fuses, relays, grounds, switches and multiplexed networks. Sensors may be analogue or digital; actuators need supply, ground and control. CAN and LIN buses require correct termination, twisted pairs and module wake-up behaviour. High-voltage systems demand isolation, PPE and manufacturer procedures.
Traps
A test light can load a sensitive circuit or fail to reveal a high-resistance connection; use a meter and wiring diagram. Resistance testing must be done with the circuit off and the component isolated; voltage-drop testing under load is often better. A battery that reads 12.6 V at rest may still fail a load test. Do not assume a module is faulty because communication codes are present: check powers, grounds and bus voltage first. Replacing a blown fuse without finding the cause invites a repeat failure.
Worked example
For a slow crank: measure battery voltage during cranking at the battery posts, then at the starter feed and engine block. A drop of more than about 0.5 V on a cable or connection under load indicates excessive resistance. Rule of thumb: test voltage drop under load, not open-circuit resistance alone.
Exam approach
Work from power and ground outward to the signal. Use the wiring diagram, confirm circuit operation, and avoid parts-swapping without a measured fault.