SMAX Temperature Sensor Fault

Incorrect temperatures and a slow warm-up on a diesel S-MAX? Is the engine actually overheating, or just reporting it? Because if it's not overheating and taking ages to warm up, and the check engine light's on, sounds like your cooling grille might be stuck closed! Does your S-MAX have the active grille shutters?

Yes, it has active grille shutters. If that's the problem, what's the next step?

If you've got active grille shutters and those symptoms, it's almost certainly the culprit. Could be a faulty sensor, a broken motor, or even just a wiring issue. Honestly, with those shutters being electronically controlled and impacting engine temps, I'd get it to a workshop. Could save you from a bigger headache (and bill) down the road. They'll have the diagnostic tools to pinpoint the exact problem.

I took it to a workshop. It was a defective fuse for the active grille shutter system. The repair was 52€. It's all working now, and the symptoms are gone.