ABS Low Brake Fluid Circuit
What does C0128 mean?
The C0128 code means the vehicle's onboard diagnostic system has detected: ABS Low Brake Fluid Circuit. This is a critical severity code.
Common Symptoms
- ABS warning light on
- Brake warning light on
- Low brake fluid level in reservoir
- Spongy brake pedal
- Longer stopping distances
Probable Causes (Ranked by Likelihood)
- Low brake fluid level from worn brake pads Very High
- Brake fluid leak at a caliper, line, or hose High
- Faulty brake fluid level sensor in master cylinder reservoir Moderate
- Corroded sensor connector or wiring Moderate
- Master cylinder internal leak Low
Step-by-Step Diagnostic Procedure
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Check brake fluid level in the master cylinder reservoir
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Inspect all four brake calipers and hoses for fluid leaks
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Check brake lines underneath the vehicle for rust-through or damage
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Test the brake fluid level sensor by unplugging and reconnecting it
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Inspect brake pads -- low pads cause fluid to fill the calipers, lowering reservoir level
Frequently Asked Questions
Why is my brake fluid low?
The most common reason is worn brake pads. As pads wear down, the caliper pistons extend further, which draws more fluid from the reservoir. Topping off fluid without replacing worn pads is only a temporary fix.
Can I just add brake fluid to fix C0128?
If brake pads are worn, adding fluid is a temporary fix -- you need new pads. If there is a leak, adding fluid will not fix it and is dangerous. Always determine why the fluid is low before just topping it off.
Is it dangerous to drive with low brake fluid?
Yes. Low brake fluid can cause brake failure. If the level drops below the minimum mark, air can enter the brake lines causing a soft or non-functional brake pedal. Do not drive the vehicle until the cause is found and fixed.