Vehicle knowledge and technical operation of the vehicle
This domain tests the daily care and technical understanding that keep a heavy vehicle legal and controllable: pre-trip inspection, brakes and air systems, tyres, emissions systems, warning lamps, and safe coupling of tractor and trailer.
Daily inspection
Walk around the combination before the first trip: tyres, tread and pressures, lights and reflectors, mirrors, leaks under the engine, coolant and oil levels, AdBlue, washer fluid and load-securing equipment. Start the engine and watch air pressure build; listen for leaks and confirm the low-pressure warning goes out before moving. Test the service brake, parking brake and trailer brake.
Systems you must understand
ABS and EBS prevent wheel lock and manage brake distribution; an amber EBS lamp means degraded braking, not "carry on". ESC, ASR and the retarder are safety systems. Diesel particulate filters need periodic regeneration at temperature - repeated short urban runs clog them. SCR uses AdBlue at roughly 3–5% of diesel consumption; running the tank dry derates the engine.
Coupling
Check that the fifth-wheel jaws are closed and the release handle secured, the kingpin greased, the landing legs fully raised, the air lines connected in the right order, the electrical cable seated and the trailer brake released before pulling away. Do a tug test.
Worked example
On a pre-trip check the air pressure stalls at 6 bar. Reasoning: the compressor or a circuit is leaking and the parking brake may not release fully, so the vehicle is unroadworthy. Report it and have it repaired rather than "trying it later".
Traps
- Treating amber warnings as cosmetic.
- Checking tyre pressure hot and adjusting down.
- Opening a hot cooling system.
- Riding the brakes down a long descent.