Chassis, generic

C0128 Low Brake Fluid Indicated

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

C0128 is not part of the accessible J2012 tables. GM lists it among its chassis codes in bulletin PIP5094, and the GM-based ABS table published by AA1Car words it Low Brake Fluid Circuit Low. The input comes from the level switch in the master cylinder reservoir: a float carrying a magnet closes a reed contact once the fluid drops, as patents from ITT and from Nabco/Nissan show. FMVSS 135 requires the red brake warning to light when the level falls below the maker's safe mark or a quarter of a compartment, whichever is higher. A genuinely low level usually means worn pads or a leak and calls for a brake check before driving on; a full reservoir with the code points to a stuck float, a shorted switch or chafed wiring.

Likely causes

Fluid level genuinely low from pad wear or a leak
Stuck float or shorted reed switch in the reservoir
Chafed switch wiring shorted to ground

Symptoms

  • Red brake warning lamp or low fluid message
  • Possibly longer pedal travel if fluid is really missing

Repair estimate

DifficultyEasyDIY possible
Parts and labour€10–400
Time0.2–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

brake fluid level switchmaster cylinder reservoir

Related codes

C0201

References: static.nhtsa.gov, aa1car.com, law.cornell.edu, patents.google.com.