🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Temperature Sensor B Circuit High
This code is a Chassis code monitored by the Electronic Brake Control Module (EBCM), which also manages the electric brake booster assembly. Code C057A indicates that the EBCM has detected a voltage reading from the ‘B’ temperature sensor circuit of the brake booster pump/motor assembly that is higher than the expected calibrated range. This sensor monitors the internal operating temperature of the electric brake booster unit to prevent overheating during repeated hard braking or pump cycling. A ‘circuit high’ fault typically points to an open circuit, a short to a voltage source, a corroded connector pin, or a failing sensor element within the booster assembly itself. When this fault is active, the EBCM may restrict brake assist functions, disable certain stability control features, or trigger a warning light on the instrument cluster to alert the driver that reduced power assist braking may be present.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair involves diagnosing a sensitive sensor circuit integrated into the electric brake booster module, which often requires specialized scan tools capable of reading bi-directional EBCM data and performing module resets or bleeding procedures. Due to the safety-critical nature of brake assist systems and the need for precise connector and wiring diagnostics with a digital multimeter, this is not recommended as a DIY repair.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and connector leading to the brake booster assembly for signs of chafing, corrosion, melted insulation, or loose pins. Check the ground connections near the booster pump housing, as a poor ground can mimic a high-voltage signal reading. - Step 2: Diagnostic Verification
Using a capable scan tool, access the EBCM module data stream and observe the live voltage reading for Temperature Sensor B. Compare this reading to Temperature Sensor A (if equipped) to see if there is a discrepancy. Backprobe the connector with a digital multimeter to confirm whether the voltage matches the scan tool reading; a reading pegged near 5V or system voltage typically confirms an open circuit or short to power. - Step 3: Resolution & Reset Process
If wiring and connectors test correctly but the voltage remains abnormally high, the internal temperature sensor within the brake booster pump assembly has likely failed and the booster unit must be replaced as the sensor is not typically serviced separately. After replacement, use the scan tool to clear the stored fault code and perform any required brake system bleed or calibration procedure specified for the electric booster unit to ensure proper reinitialization.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: OEM-level bi-directional scan tool, digital multimeter, replacement electric brake booster/pump assembly, electrical contact cleaner
- Average Component Price: $250 – $650 USD
- Estimated Labor Hours: 1.5 – 3.0 hours
- Total Estimated Budget: $400 – $900 USD