🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor A Phase U-V-W Circuit Range/Performance
This is a Chassis-side diagnostic trouble code monitored by the Electronic Brake Control Module (EBCM), which is responsible for managing the electric brake booster assist system. The code indicates that the EBCM has detected a Range/Performance fault on the three-phase (U, V, W) motor winding circuit that drives the brake booster’s electric motor/pump assembly. This motor is responsible for generating hydraulic or vacuum-equivalent assist pressure to help the driver apply braking force. A ‘Range/Performance’ designation specifically means the module is seeing electrical feedback from the U-V-W phase windings that falls outside of expected parameters during motor operation — this is different from a simple open or short circuit, and instead suggests the motor is turning unevenly, struggling under load, has excessive internal resistance, or the EBCM is receiving inconsistent position/rotation feedback from the phase circuits. This condition can lead to reduced brake assist, a stiff brake pedal, illumination of the brake warning or stability control indicator lamps, and in some cases disabling of the traction control and stability control systems as a protective measure. This is strictly an ABS/brake booster chassis concern and has no relationship to engine or powertrain operation.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires a professional-grade scan tool capable of reading EBCM-specific live data (motor phase current, duty cycle, and feedback voltages) as well as a digital multimeter capable of measuring AC ripple and resistance across three-phase windings. Because this code involves a safety-critical brake assist system, improper diagnosis or repair carries significant liability, and any wiring or motor replacement work should be followed by proper bleeding procedures and module calibration using dealer-level or OEM-equivalent diagnostic software.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and connector leading to the brake booster motor assembly for signs of chafing, corrosion, pinched wires, or water intrusion. Check the connector pins for looseness or corrosion, and confirm that the EBCM itself has no visible signs of moisture damage or burnt connections. Inspect the brake booster motor housing for any unusual noise, binding, or physical damage that could indicate internal motor failure. - Step 2: Diagnostic Verification
Using a capable scan tool, access EBCM live data streams and monitor the U, V, and W phase voltage and current readings while activating the brake booster motor (via a bi-directional control test if available). Compare these readings against OEM specifications to identify irregular current draw, voltage dropout, or phase imbalance. Follow this with a static multimeter test across each of the three phase wires to check winding resistance values — all three legs should read nearly identical resistance. Significant deviation on any single phase points to a bad motor winding, while identical abnormal readings across all phases may indicate a wiring or EBCM driver circuit issue. - Step 3: Resolution & Reset Process
If testing confirms a wiring or connector fault, repair or replace the damaged harness section and reseal connections to prevent future corrosion. If the motor winding resistance is out of specification or the motor fails to respond correctly under bi-directional testing, the brake booster motor/pump assembly will need replacement as a unit. After repair, clear the stored fault code, perform a system bleed if required by the booster design, and run the manufacturer-specified EBCM relearn or calibration procedure to confirm the motor phase feedback returns to normal operating range before road testing the vehicle.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake booster motor/pump assembly, wiring harness repair kit or connector (if needed), OEM-level or professional bi-directional scan tool
- Average Component Price: $250 – $650 USD (brake booster motor assembly)
- Estimated Labor Hours: 1.5 – 3.0 hours (includes diagnosis, replacement, bleeding, and calibration)
- Total Estimated Budget: $400 – $950 USD