🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor B Phase U-V-W Circuit Range/Performance
This code is set by the Electronic Brake Control Module (EBCM) when it detects an electrical range or performance fault within the three-phase (U, V, W) winding circuit of the electric brake booster’s internal motor. Modern brake booster assemblies use a brushless DC motor to provide hydraulic assist independent of engine vacuum, and this motor relies on precise phase sequencing between the U, V, and W windings to rotate smoothly and apply correct brake assist pressure. When the EBCM commands a specific torque output but the feedback signal from the motor’s phase circuits falls outside the expected voltage, resistance, or timing range, it indicates a performance degradation rather than a complete circuit failure. This can stem from a partially shorted winding, degraded motor bearings causing rotational resistance, corrosion at a booster motor connector, or an internal EBCM driver stage fault. Because this directly affects brake pedal assist and stopping power, this code often triggers a reduced brake assist mode, illuminated brake warning lamp, and traction/stability control deactivation until the fault is cleared.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires specialized bi-directional scan tool access to communicate directly with the EBCM, along with a digital multimeter capable of measuring low-resistance three-phase motor windings. Because the brake booster assembly is a safety-critical hydraulic component requiring brake system bleeding, pressure bleeding equipment, and potential module calibration after replacement, this is not recommended as a DIY repair.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Visually inspect the brake booster motor wiring harness and connector for corrosion, frayed insulation, or loose pins at the EBCM and booster motor connector. Check for signs of brake fluid contamination near the connector, as fluid intrusion is a common cause of phase circuit degradation. - Step 2: Diagnostic Verification
Using a scan tool, access EBCM-specific data streams and command a booster motor actuation test while monitoring live U-V-W phase voltage and current values. Follow up with a digital multimeter to measure resistance across each phase winding pair at the connector (with the harness disconnected and ignition off), comparing readings to OEM-specified winding resistance values to identify an imbalance between phases. - Step 3: Resolution & Reset Process
If a winding imbalance or out-of-range resistance is confirmed, the brake booster motor/pump assembly will need to be replaced as a unit, since individual phase windings are not serviceable. After replacement, the brake hydraulic system must be properly bled using the scan tool’s brake bleed procedure, and the EBCM should undergo a booster motor calibration/relearn sequence. Clear the stored code and perform a road test with hard brake applications to confirm no code resets and that brake assist and feel are restored to normal.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: OEM Electric Brake Booster/Pump Motor Assembly, Bi-Directional Scan Tool with Brake Bleed Function, Digital Multimeter, Brake Fluid (DOT 3/4 as specified)
- Average Component Price: $350 – $950 USD
- Estimated Labor Hours: 2.5 – 4.0 hours
- Total Estimated Budget: $600 – $1,450 USD