P2026 Fault in 2006 Smart Fortwo: Lights On Triggering Dashboard Warning Lines

Dear Team, I recently noticed three lines appearing on the dashboard of my 2006 Smart Fortwo whenever I turn on the headlights. The warning triangle also activates at this time. I have already replaced all the light bulbs, and they function properly—yet the issue persists. Every time I switch on the lights, the dashboard lines and warning symbol reappear. A mechanic performed a diagnostic check and identified fault code P2026. I'm confused because the problem only occurs when turning on the headlights. How can this be resolved? What could be causing this specific behavior? Any insights or solutions for owners of 2006 Smart Fortwo experiencing this issue would be greatly appreciated.