Seat Formentor Diesel Preheating Issue

Sounds like a similar issue I had with my Formentor. The preheating lamp stayed on, and the check engine light popped up. Have you checked the glow plugs themselves? Sometimes a faulty glow plug can trigger those symptoms.

Thanks for the suggestion. I haven't checked the glow plugs individually. Where are they located, and is it a straightforward process to test them? I'm reasonably handy, but I don't want to mess with the ignition system if it's too complex.

It could be the glow plugs, but more likely it's the heating module itself. Same thing happened to me, and while glow plugs are a common culprit, the diagnostics pointed to the control unit. Unless you have the proper diagnostic tools, I'd suggest taking it to a workshop. They can pinpoint the exact fault within the car preheater system.

Thank you for the input. It turned out to be a defective cable connection to the preheating control unit, as suspected. The repair cost me 95€, which is much better than replacing the entire heating module.