Vectra preheating lamp issue

Sounds familiar! I had a similar issue with my Vectra (diesel too). Engine light was on, and it was like driving a tractor on a cold morning. Have you checked the glow plugs themselves? Could be a simple fix.

I haven't yet, but you're right, that's next. Did your Vectra also have the preheating lamp staying on constantly, like it's stuck in some kind of loop?

Yep, that preheating light was always on! After a week, I took it to a workshop. Turned out to be a faulty glow control unit, just like you suspected. Saved me a headache.

Thanks! Took it to the workshop. You nailed it: faulty glow control unit and dodgy connection. Cost me 95€, but at least the smoke screen is gone. Appreciate the help!