C3 Diesel Preheating Lamp Issue

Whoa, that sounds like a headache! My C3 had a similar engine light issue once, and it turned out to be a dodgy sensor. Have you checked the basics like battery voltage and the glow plug relays? Sometimes it's the simple stuff that throws us off. Also, that smoke could be serious - what color is it?

Thanks! Battery voltage seems okay. The glow plug relays need a closer look. How do I check those? The smoke is greyish.

Greyish smoke points to incomplete combustion, which aligns with your glow control unit idea. If the relays seem okay, honestly, with those symptoms, it’s probably beyond basic DIY. Get it hooked up to a proper diagnostic tool, or just take it to a workshop before you do more damage. Playing around too much with a diesel engine without the right gear can be a really bad move.

Understood. I took it to a workshop. They found a defective cable connection to the glow control unit and replaced it. Total cost was 95€ Thank you!