System: Chassis (C-Code)
SAE Standard (Generic)
Family: Brake Fluid Level Wear Sensor Circuit
Code C004B: Brake Fluid Level Sensor/Switch Circuit/Open
Diagnostic & Technical Explanation
Code C004B (Brake Fluid Level Sensor/Switch Circuit/Open) sets when the module detects a low brake fluid condition, an open circuit at the fluid level float switch, or an open circuit in a brake pad wear-indicator wire, all of which share a simple low-current warning-lamp circuit rather than a precision sensor. The most common causes are fluid dropping below the float threshold from worn brake pads taking up caliper piston travel, a float switch stuck in one position, or a wear-indicator wire that has been ground through by a worn-out brake pad backing plate. Because this circuit is directly tied to the low-brake-fluid warning lamp, it is worth confirming actual fluid level and pad thickness before assuming an electrical fault.
First-listed procedure
Rank #1
Check brake fluid level and top off
Easy DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: Brake Fluid Level Wear Sensor Circuit
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)