Twingo preheating lamp stays on

I had a similar issue with my Opel Corsa, but it was a petrol engine. The glow plug light stayed on, and it was a faulty connection to the ignition system. Have you checked the fuses?

Thanks! I'll check the fuses. When you say faulty connection to the ignition system, do you mean the cable or plug connection? Is it worth checking the control unit?

Yeah, in my case, it was the cable connection. I'm no expert, but with those symptoms, a defective cable or plug connection could be the problem. I'd take it to a workshop; they can diagnose it properly.

Thanks so much! Took it to the workshop, and you were right. It was a defective cable or plug connection. The preheating control unit needed replacing. The repair was 95€.