DASHBOARD WARNING
“Brake system fault - stop carefully”
Applies to: Audi
What it means
The car has detected a fault in the braking system and is asking you to stop. On Audi models using the Bosch ESP9 ABS unit this message can appear with the code C123EF0, where the ABS/ESP unit has switched off hydraulic brake assist.
Typical symptoms
- Red brake warning light
- ABS and traction control lights on
- Brake pedal feels hard or lacks assistance
Safety guidance
Do not drive
Stop somewhere safe as soon as you can and do not continue driving. Braking assistance may be reduced.
This guidance applies to: Audi models from 2015 with Bosch ESP9 ABS units, plus some VW and Bentley models.
Common causes
- A brake booster vacuum or pressure sensor fault recorded repeatedly
- Vacuum supply problems (vacuum pump, hoses, servo)
How we diagnose and fix it
We read the stored codes, test the vacuum and sensor circuits, then repair the underlying fault and the affected unit. Book a diagnostic so we can test the car in person.
Related services
Business-supplied dashboard message and guidance.
Get this checked
A fault code on its own does not confirm a diagnosis, and a code lookup cannot tell you whether your vehicle is safe to drive. Book a diagnostic and we will test the car in person.
- Basic Diagnostic Check – £45 (Autel MS906)
- Security-locked vehicles – £80–£150 depending on make and model
Priced after diagnostic check, agreed with you before any further work.
A booking request is not a confirmed appointment: the garage confirms availability with you, and any further work is agreed with you before it starts.
