Mokka Preheating Lamp and Smoke

Sounds like a preheating issue. Since you're seeing smoke, it might be more than just the glow plug light. Have you checked the glow plugs themselves or just the control unit connection?

I've only looked at the control unit connections and wiring for damage. I haven't checked the glow plugs. Is there an easy way to test them without removing them?

Testing glow plugs in place is tricky without special tools. Given the symptoms and mileage, it's likely a defective part. I'd get it checked at a workshop rather than trying to diagnose it yourself.

Thanks for the advice. The workshop confirmed it was the preheating control unit, specifically a faulty plug connection. Repair cost was 95€. Problem solved.