Thalia hard steering and vibration

Sounds familiar. I also drive a Thalia. I had similar symptoms a while back: hard steering, vibrations. Have you checked your wheel alignment? A bad alignment can put extra strain on the power steering system and steering angle sensor, or the electronic stability program.

Thanks. I haven't checked the wheel alignment specifically. Could a faulty coding of the steering angle sensor cause these problems, including the electronic stability?

Yes, incorrect coding or a failing steering angle sensor can definitely cause those issues. It affects the signal sent to the power steering and stability control. If the sensor provides the wrong data the alignment will be off. I ended up having to take mine to a workshop to get it sorted. It's a pain, but worth it for safety.

Thanks for the advice. I had the steering angle sensor replaced and re-coded at a workshop. The repair cost 195€. Seems to have resolved the issues. Much appreciated!