Vehicle Maintenance, Servicing, and Diagnostics
Domain 7 tests scheduled servicing, systematic fault-finding and correct use of test equipment.
Servicing
Daily checks cover engine oil, coolant, brake fluid, tyre pressure and tread, lights and wipers. Periodic services at set kilometre intervals replace engine oil, oil filter, air filter and fuel filter, and inspect belts, brakes, suspension, battery and steering. Preventive maintenance is planned; breakdown maintenance follows a failure. Keep a job card and record every replacement.
Diagnostics
Read fault codes (DTCs) with a scan tool through the OBD-II port, then test the circuit - a code points to a system, not a specific failed part. A compression test reveals ring, valve or gasket faults; a vacuum gauge or smoke test finds intake leaks. Exhaust colour: white = coolant burning, blue = oil burning, black = rich mixture.
Worked example
A tyre is worn on both shoulders. Reasoning: the centre of the tread bows outward when pressure is low, so the shoulders carry the load - the cause is under-inflation. Wear only in the centre means over-inflation; wear on one edge means camber or toe error; patchy wear means imbalance or worn dampers. Check pressure cold before suspecting alignment.
Traps that cost marks
Erasing codes without repairing the fault; checking tyre pressure when hot; condemning a battery without a load test; treating white smoke on a cold morning as a fault when it is condensation; using a torque wrench to loosen nuts.