Saxo brake pedal vibration

Interesting. Undervoltage affecting the brakes is plausible, especially if it's an intermittent issue. Are you sure your brake rotors are fine? Warped rotors can cause pedal pulsation. It could also be an issue with the hydraulic system itself, or even just worn brake pads. Have you checked those? Are they metal brakes or do you have brake shoes at the back?

Thanks for the quick response! I haven't physically checked the rotors or pads myself, but I've had a quick look and they seem OK. How would undervoltage actually affect the brakes? Is it like when you don't give enough energy to the motor?

Think of it like this: the ABS system relies on consistent power to function correctly. If you're getting voltage drops, the ABS modulator might be glitching, causing that pulsing sensation. That said, brake issues can be tricky to diagnose remotely. Given your symptoms and the age of the car, I would strongly recommend taking it to a workshop to get the brake system thoroughly inspected. It could be many things.

Thanks for the advice, I appreciate it! I took it to a mechanic and you were right, it was more complex than just a simple voltage issue. Turns out I needed new brake pads and rotors. The whole job came to around 240€. Thanks again for pointing me in the right direction!