Cold-start faults on a Euro VI tractor unit
A 2019 Euro VI 6x2 tractor unit has been parked overnight at -18 °C. At 05:30 the driver starts the engine; it runs roughly for 10 minutes, then the yellow engine warning lamp comes on and torque is limited to about 60%. The dashboard shows an AdBlue warning 'SCR efficiency low' and a DPF regeneration request. The driver added 20 litres of AdBlue from a plastic can that had been stored in an unheated container since last winter. The air pressure gauge shows 7.8 bar and rising slowly on circuit 1; circuit 2 is at 8.2 bar. The fuel filter has a water-in-fuel warning. The driver must leave at 06:00 for a 3-hour drive to a terminal.
1. Diagnose the most likely causes and rank them by safety criticality.
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The most safety-critical item is the air pressure. Circuit 1 is only 7.8 bar and rising slowly, which suggests a leak or a frozen air dryer or drain valve. A vehicle must not depart with a slow pressure build or a pressure drop. Next is the fuel system: the water-in-fuel warning at -18 °C raises the risk of paraffin gelling and filter blockage, which can stop the engine. The rough running and derate may be caused by fuel starvation as well as by the SCR fault. The AdBlue warning is likely caused by contaminated or diluted AdBlue from the old can, or by a frozen DEF line that has not thawed; SCR efficiency low will eventually derate the engine. The DPF regeneration request is probably caused by cold idling and short operation, but it is less immediately critical than air and fuel. Rank: air pressure, fuel quality, AdBlue/SCR, DPF.
2. What should the driver do before departure, and what should he not do?
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Before departure, drain the water from the fuel filter and check that the vehicle has winter-grade diesel. Only approved anti-gel additive should be used, following the manufacturer's instructions. Do not add petrol, kerosene or ether; those can damage the engine and fuel system. Check the air system for leaks, drain the air tanks and allow pressure to build to the normal operating range. If circuit 1 remains slow or drops, the vehicle is defective and must not be driven. For AdBlue, do not top up with more from the old can. If possible, drain and refill with AdBlue that meets ISO 22241 from a clean source, then allow the SCR system to thaw and run. For the DPF, a steady-speed drive may allow regeneration, but idling will not fix it. If the derate remains at 06:00, the driver should not leave; the workshop or recovery must be called.
3. How does the fault affect driving and rest time, and what are the driver's obligations if the vehicle is not ready at 06:00?
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If the vehicle is not ready at 06:00, the driver must not drive it. The time spent waiting for repair or recovery is not driving time. Depending on whether the driver is free to rest, it may be recorded as break, rest or availability; it must not be recorded as driving. The driver must inform the dispatcher, record the delay honestly and avoid manipulating the tachograph to hide the waiting time. If the delay threatens the daily or weekly driving limits, the transport must be replanned. The driver also has a duty to refuse to drive an unsafe vehicle, even if the customer is waiting. The correct sequence is: report the defect, get authorisation for repair, record the time correctly, and only depart when the air, fuel and emissions faults are resolved or the vehicle is cleared by a workshop.