C0230 C0xxx · Chassis (C) High severity
Brake Booster / Vacuum or Electric Assist Sensor Fault
The brake assist system cannot verify booster performance. Pedal effort may increase and braking distances can lengthen.
Severity guidance: High — stop driving and diagnose now; risk of further damage
Symptoms you will notice
- Hard brake pedal
- Longer stopping distance
- Brake warning lamp
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed boost pressure sensor
- 2 Vacuum leak to the booster
- 3 Faulty electric vacuum pump
- 4 Wiring fault
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Check pedal feel first — a genuinely hard pedal means assist is lost.
- ✓ Inspect vacuum hoses and the one-way valve.
- ✓ Test the electric vacuum pump where fitted.
- ✓ Read live boost pressure and compare with specification.
Repair options
- Replace the vacuum hose or one-way valve
- Replace the vacuum pump
- Replace the boost sensor
C0230 — frequently asked questions
Is it safe to drive? +
If the pedal is hard, braking distance increases significantly. Have it recovered rather than driven.
Why is it worse on a cold start? +
A leaking one-way valve or weak pump shows up before manifold vacuum stabilises.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.