C0100 critical

Brake Fluid Level Sensor Circuit Malfunction

The C0100 code means the vehicle's onboard diagnostic system has detected: Brake Fluid Level Sensor Circuit Malfunction. This is a critical severity code.

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Keep driving?: Short distances only
DIY difficulty: easy
Estimated cost: $10 - $300 (parts and labor)

Read ABS Codes

BlueDriver Bluetooth Pro Scanner

Basic scanners cannot read ABS codes. BlueDriver reads all systems including ABS, SRS, and transmission through your phone.

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Read ABS Codes

LAUNCH CRP123X (Reads ABS + Chassis)

Basic scanners cannot read ABS codes. This one reads all four systems so you know exactly which sensor failed.

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Common Symptoms

Brake warning light on dashboard
Low brake fluid warning message
ABS and traction control lights on
Brake fluid level reads incorrect
Warning light on but fluid level appears normal

Probable Causes (Ranked by Likelihood)

Low brake fluid level due to worn brake pads Very High
Faulty brake fluid level sensor in reservoir High
Brake fluid leak in system Moderate
Corroded sensor connector Low

Step-by-Step Diagnostic Procedure

Visually check brake fluid level in master cylinder reservoir
Inspect brake lines and calipers for leaks
Check brake pad thickness at all wheels
Test fluid level sensor by raising and lowering float manually
Check sensor connector for corrosion

Frequently Asked Questions

Why does brake fluid drop when brake pads wear?

As brake pads wear thin, the caliper pistons extend further out, taking up more fluid from the reservoir. This is normal and the fluid level will drop as pads wear.

Should I just add brake fluid to fix this?

Only add fluid after checking for leaks and inspecting brake pad thickness. If the fluid is low because pads are worn, adding fluid without replacing pads masks the real problem.

Is a brake fluid leak dangerous?

Yes. A brake fluid leak can lead to partial or complete loss of braking ability. If you see fluid on the ground or a sudden drop in the reservoir, do not drive and have the vehicle towed.