C055D: Brake Hydraulic Circuit B Leak

Brake Hydraulic Circuit B Leak: a leak has been detected in this brake-hydraulic circuit, which reduces braking pressure. Safety-critical.

High severity. Can I keep driving?The regular brakes usually keep working, but without ABS or the driver aids. Drive very carefully and go to a repair shop; if the pedal feel changes, do not keep driving.

Symptoms

ABS warning light on
ESC/stability control deactivated
Possible reduced brake assist
Speedometer may behave erratically

Most likely causes

Brake fluid leak in circuit B

What to check, in order

Start with the simplest. You can tick off each step.

Check that the brakes respond normally and check the fluid level
Read the ABS codes with a multi-system scanner
Check the wheel sensors, connectors, and wiring
Compare the speeds of all four wheels in live data
Leave any work on the hydraulic circuit to a professional

Good to know

Repair difficulty: hard
It can trigger limp mode.

What each character of C055D means

C: Chassis
0: Generic code: same on every make
5: Subsystem depends on the code range
5D: Specific fault in that system

Frequently asked questions

Can I keep driving with code C055D?

The regular brakes usually keep working, but without ABS or the driver aids. Drive very carefully and go to a repair shop; if the pedal feel changes, do not keep driving.

What causes code C055D?

The most common causes are: brake fluid leak in circuit B.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.