C5 Electronic Parking Brake Failure

The symptoms suggest a problem within the electronic parking brake system. The error message and warning light back up the lack of function. Given the hybrid nature of your C5, diagnostics can be complex. Before component-level troubleshooting, have you checked the vehicle's 12V battery condition? A weak battery can cause spurious electronic faults. Also, are there any other error messages related to the ABS or stability control systems, as they are often interconnected with the parking brake?

Thank you. The 12V battery appears to be in good condition, and there are no other error messages related to the ABS or stability control systems. What would you recommend as the next step?

Given that the battery is sound and no other related systems are reporting errors, the most probable cause points towards a defect in the electric motor within one or both of the rear brake calipers. These motors are known to fail, particularly at higher mileage. The next step would ideally involve a diagnostic scan using Citroen-specific diagnostic equipment to pinpoint the affected caliper. Repair often entails replacing the entire caliper assembly. I'd recommend taking your vehicle to a reputable workshop with experience in Citroen electronic brake systems for a proper diagnosis and repair.

I appreciate the explanation. Based on your assessment, I took the vehicle to a workshop, and the diagnosis confirmed a defective electric motor in the brake caliper. The repair, including parts and labor, came to 505€. Thank you for your assistance in identifying the likely cause.