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.
What C055D means
C055D is a generic OBD-II chassis code in the ABS & brakes group. In plain English: the computer found an electrical fault in that circuit: an open, short or bad connection, or a failed component.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Yes
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
Common causes
- 01Brake fluid leak in circuit BMost likely
Can I drive with C055D?
Not recommended beyond getting it to a shop.
This fault can put the vehicle in limp mode with reduced power, which can make merging and passing unsafe. Have it diagnosed as soon as possible.
Why we rate it urgent
- Can put the vehicle in limp mode (reduced power)
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose C055D
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just C055D. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for C055E, C05B0, C05B1. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Test the circuit
Inspect the wiring and connector at the brake circuit b for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Brake fluid leak in circuit B. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
C055D repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- Brake circuit B
C055D FAQ
What does C055D mean?
C055D means “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.
Is C055D serious? Can I keep driving?
We rate C055D as urgent severity. Not recommended beyond getting it to a shop. This fault can put the vehicle in limp mode with reduced power, which can make merging and passing unsafe. Have it diagnosed as soon as possible.
What causes C055D?
The most common causes, from most to least likely: Brake fluid leak in circuit B. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix C055D?
Typical labor is about $125–$750 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix C055D myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will C055D clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.