Viano Diesel engine power loss and smoke

A defective diesel particulate filter (DPF) is indeed a common issue, particularly with the symptoms you describe. I had a similar experience with my Vito, though I didn't see smoke. The engine light is a key indicator. Before jumping to a filter replacement, which can be expensive, have you tried initiating a regeneration cycle? Sometimes, the filter becomes clogged, and a forced regeneration, either through the vehicle's computer or by a workshop, can clear it. It might be worth investigating if there are any fault codes related to the differential pressure sensor. This sensor monitors the pressure difference across the DPF; a faulty reading can prevent regeneration and lead to the symptoms you're seeing.

Thank you for the information. Could you elaborate on the regeneration cycle? I am unfamiliar with the procedure and whether it is something I can perform myself or if it necessitates specialized equipment.

Certainly. Regeneration is essentially a process where the exhaust system raises the temperature of the DPF to burn off accumulated soot. There are typically two types: passive and active. Passive regeneration occurs automatically during normal driving at higher speeds and engine loads. Active regeneration is triggered by the engine control unit (ECU) when the soot load reaches a certain threshold. If your driving style is mostly short trips, passive regeneration might not occur frequently enough. A forced, active regeneration requires a diagnostic tool to command the ECU to initiate the process. If the engine light is on, it is likely that the ECU has already tried and failed to regenerate the filter. Given your description, and the fact that you are seeing smoke, I would recommend taking it to a workshop to have the exhaust system and the DPF thoroughly inspected. A sensor fault could also be preventing regeneration, but with the engine light on and smoke present, it may be beyond a simple fix.

I appreciate the comprehensive explanation. I will heed your advice and schedule an appointment with a qualified workshop to conduct a thorough inspection of the exhaust system, including the DPF and associated sensors. They have confirmed the DPF is defective and the filter replacement with a new unit will cost 1550€. Thank you again for your assistance.