C2 Brake Booster Pressure Sensor Fault

The symptoms you're describing do sound like a faulty brake booster pressure sensor, especially considering the error code. Has any work been done on the brake system recently, perhaps involving bleeding?

Yes, I had the brake lines flushed and bled about a month ago after replacing a caliper. Is it possible they didn't do it properly?

It's certainly plausible that an improper bleeding procedure could lead to air in the system, affecting the brake booster's performance and triggering the sensor. Given the potential safety implications with the ABS system and braking, I strongly advise having a workshop inspect the entire system. It could prevent more damage.

Thanks for the advice. I took it to a shop, and it turned out the brake system hadn't been bled correctly, causing the pressure sensor to fail. They re-bled the system and replaced the sensor. Total cost was 90€. All sorted now!