C004B Brake Fluid Level Sensor/Switch Circuit/Open

Covers an electrical fault, specifically an open or out-of-range circuit, in the brake fluid level sensor or switch, as opposed to C0049 which reports an actual low-level condition. The float switch or level sensor in the reservoir provides a defined signal to the brake or stability module; this code is set when that circuit is open, shorted or gives an implausible value so the module can no longer trust the level reading. Because the level warning is a safety function, the module may illuminate the red brake warning indicator and treat the level as unknown. A fault is usually a broken wire, a corroded connector or a failed switch rather than low fluid itself. Patents show the usual float magnet acting on a reed or Hall switch. No manufacturer documents this code publicly.

Likely causes

Symptoms

• Red brake warning indicator on
• Brake fluid level reads as unknown
• Intermittent low-fluid warnings

Repair estimate

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

Parts involved

Related codes

References: patents.google.com, rosap.ntl.bts.gov, en.wikipedia.org.