🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor “B” Performance
This code is a Chassis code and is monitored by the Electronic Brake Control Module (EBCM) or an associated Power Steering/Brake Booster control module. The fault indicates that the secondary (or redundant) booster motor circuit — labeled Motor “B” in multi-motor electric brake booster assemblies — is not performing within the expected parameters set by the module. This typically occurs on vehicles equipped with an electro-hydraulic or fully electric brake booster system, where two internal motors work together to generate the hydraulic pressure needed for brake assist. When the EBCM commands a specific pressure output from Motor B but the resulting feedback signal (via internal position sensors or pressure transducers) falls outside of the expected range, this code sets. Causes can include a failing booster motor, a degraded motor control circuit, excessive resistance in the wiring harness, a weak vehicle battery/charging system causing voltage starvation, or an internal fault within the booster pump assembly itself. This is a safety-critical code because it directly affects brake pedal assist and stopping power; the vehicle may exhibit a hard brake pedal, reduced brake assist, illuminated ABS/Brake warning lights, or a disabled traction/stability control system.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
Diagnosing and repairing this code requires a bi-directional scan tool capable of actuating the brake booster motors individually, along with a digital multimeter to check voltage drop and resistance across the motor control circuits. Because this fault affects the hydraulic brake assist system, any misdiagnosis or improper repair carries significant safety liability, and the booster assembly itself often requires special bleeding procedures and module calibration only available through professional-grade scan tools.
🛠️ Resolution Steps
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Step 1: Preliminary Inspection
Begin by visually inspecting the electric brake booster assembly, typically located near the master cylinder, for signs of corrosion, loose connectors, or damaged wiring harnesses. Check the vehicle’s battery voltage and charging system output, as voltage irregularities are a common cause of motor performance faults in these systems. Inspect the ground straps near the booster assembly for corrosion or looseness. -
Step 2: Diagnostic Verification
Connect a capable scan tool to pull live data from the EBCM, specifically monitoring Motor B’s commanded output versus actual feedback values (voltage, current draw, or position/pressure sensor readings). Use a digital multimeter to check for proper voltage supply and ground at the motor connector with the key on, and perform a voltage drop test across the motor circuit under load if possible. Compare readings against the manufacturer’s specified values to confirm whether the fault lies in the wiring, connector, or the motor/pump assembly itself. -
Step 3: Resolution & Reset Process
If wiring or connector issues are found, repair or replace the damaged harness section and ensure connectors are properly seated and sealed. If the motor itself is confirmed faulty through testing, replace the brake booster/pump assembly as a unit (most are non-serviceable internally). After any component replacement, perform a system bleed of the brake hydraulic circuit per OEM procedure, then clear the stored code and run a verification test using the scan tool to confirm the module no longer detects a performance fault. A static or dynamic relearn/calibration procedure may also be required to fully reset the EBCM’s adaptive values.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Electric brake booster/pump assembly, wiring harness repair kit (if needed), OEM-level bi-directional scan tool for calibration
- Average Component Price: $350 – $900 USD (brake booster assembly varies widely by make/model)
- Estimated Labor Hours: 2.5 – 4.5 hours (includes diagnosis, replacement, and system bleed/calibration)
- Total Estimated Budget: $600 – $1,500 USD