🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Temperature Sensor C Circuit Range/Performance
C05B6 is a Chassis code monitored by the Electronic Brake Control Module (EBCM), which may also interface with the hydraulic brake booster control unit on vehicles equipped with electro-hydraulic or electric brake booster assist systems. This specific code indicates that the EBCM has detected a Range/Performance fault on the ‘C’ temperature sensor circuit associated with the brake booster pump/motor assembly. Rather than a complete circuit failure (open or short), a Range/Performance code means the sensor is returning a voltage signal, but that signal falls outside the expected operating parameters for current conditions — meaning the reported temperature doesn’t logically match the vehicle’s operating state (e.g., the sensor reports an implausibly high or low temperature relative to pump run-time or ambient conditions). This sensor exists to protect the brake booster pump motor from thermal damage during repeated hard braking events or ABS/traction control activations, and a fault here can cause the EBCM to restrict or disable brake assist functions, illuminate the ABS or brake warning lights, and potentially increase required pedal effort. This code strictly concerns chassis braking hydraulics and sensor circuits — it has no relationship to engine performance, Check Engine Light conditions, or powertrain operation.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires a bidirectional scan tool capable of reading live ABS/EBCM data streams and manufacturer-specific bleed/calibration procedures for the brake booster pump system. Because this code involves the hydraulic brake assist circuit, improper diagnosis or a botched repair can result in a dangerous loss of brake assist, making this unsuitable for casual DIY repair. A digital multimeter is needed for wiring and resistance checks, but final verification and system bleeding should be performed by a qualified brake systems technician.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and connector leading to the brake booster pump/motor assembly, specifically looking for the temperature sensor (sensor ‘C’) pigtail connection. Check for corrosion, chafed insulation, pinched wires near the pump bracket, or a loose/degraded ground connection. Inspect the booster pump housing for signs of overheating, fluid leaks, or physical damage that could create abnormal thermal readings. - Step 2: Diagnostic Verification
Connect a capable scan tool to the vehicle’s diagnostic port and access live EBCM data specifically for the booster temperature sensor circuit. Compare the reported temperature value against known-good baseline values at key-on/engine-off and after several brake applications. Use a digital multimeter to check resistance across the sensor terminals (with the connector disconnected and the ignition off), comparing readings to OEM-specified resistance-to-temperature charts. A reading that is erratic, fixed, or inconsistent with ambient/operating temperature confirms a sensor or wiring fault rather than a hydraulic mechanical issue. - Step 3: Resolution & Reset Process
If wiring/connector damage is found, repair or replace the affected harness section and confirm continuity. If the sensor itself is confirmed faulty via resistance testing, replace the integrated temperature sensor or, on most platforms, the complete brake booster pump/motor assembly (as the sensor is often non-serviceable separately). After repair, clear the stored DTC using the scan tool, perform the manufacturer-required brake system bleed/initialization procedure, and road test while monitoring live EBCM data to confirm the temperature sensor reads within normal range and no ABS/brake warning lights return.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: OEM Brake Booster Pump/Motor Assembly (with integrated temp sensor), wiring harness repair kit (if applicable), bidirectional scan tool with ABS module access
- Average Component Price: $180 – $450 USD
- Estimated Labor Hours: 1.5 – 3.0 hours
- Total Estimated Budget: $300 – $650 USD