Citan Diesel VANOS Issue and Fuel Consumption

A check engine light coupled with increased fuel consumption certainly suggests a VANOS issue warrants investigation. Before assuming the worst, have you verified the power supply to the camshaft solenoid valves? A faulty power supply can mimic a defective solenoid. Furthermore, is there any history of infrequent oil changes? Neglecting oil changes can lead to sludge buildup, potentially affecting VANOS operation. Could you describe the driving conditions when the check engine light initially appeared?

Thanks for the quick response. I haven't specifically checked the power supply to the solenoids, that's a good point. Oil changes have been regular, but could there still be sludge despite that? What would be the best way to verify the power supply without specialized tools?

While regular oil changes are beneficial, the quality of oil and driving habits can still contribute to sludge formation over time. Regarding the power supply, a multimeter is the ideal tool to check for voltage at the solenoid connector. However, lacking that, visually inspect the wiring for any damage or corrosion. Given the potential complexity and the symptoms presented, the most prudent course of action might be a diagnostic assessment by a qualified workshop. Do you agree?

Thanks for the advice. I took your suggestion and had it checked by a mechanic. Turns out it was a faulty camshaft solenoid valve and a wiring issue. Repair cost was around 250€. The check engine light is now off and the fuel consumption is back to normal.