Emission Control and Vehicle Inspection/Roadworthy Checks
Core concepts
Understand the major emission control systems: positive crankcase ventilation, evaporative emissions, exhaust gas recirculation, catalytic converter, diesel particulate filter and selective catalytic reduction. Know how each reduces specific pollutants and their common failure symptoms. Cover exhaust gas analysis, oxygen sensor operation and the effect of misfire on converter life. Understand roadworthy inspection requirements: braking performance, steering play, suspension condition, tyre tread and condition, lighting, seat belts, structural integrity and fluid leaks.
Traps
Questions often test whether removing a catalytic converter improves performance (it does not legally or practically) and whether a DPF can be cleaned by simply driving (passive regeneration requires specific conditions). Watch for confusion between pollutants: hydrocarbons, carbon monoxide, oxides of nitrogen and particulates each have different sources and controls.
Worked example
During a roadworthy inspection, a vehicle has a leaking shock absorber. The component is recorded as defective, the customer is advised, and the vehicle is not passed until repaired. Document the defect with a clear description and photograph, and note the customer's instructions.
Rule of thumb
Inspection is evidence-based. Record what you see, not what you assume.