🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor B Position Sensor Circuit/Open
This code is set by the Electronic Brake Control Module (EBCM) when it detects an open circuit or an out-of-range signal from the position sensor associated with Motor ‘B’ on the electro-hydraulic or electric brake booster assembly. This sensor is critical because it tells the control module the exact rotational position of the booster motor, allowing the module to precisely modulate brake pressure during both standard stops and Automatic Emergency Braking (AEB) events. If the circuit is open—meaning the wiring has broken, corroded, or a connector has backed out—the module loses the feedback signal needed to verify motor movement. Without this data, the module cannot safely command the booster motor, as it would be operating ‘blind’ regarding pedal feel and pressure application. This typically results in a hard brake pedal, loss of power assist, and the disabling of the Stability Control and Traction Control systems until the fault is cleared.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires a bidirectional scan tool capable of accessing brake module-specific data streams, as standard code readers often cannot see live sensor voltage data for internal booster components. Additionally, due to the high-pressure hydraulic nature of modern brake boosters and the safety-critical calibration required after a sensor or pump replacement, this job should not be attempted by a home mechanic. Specialized bleeding procedures and module resets are required to ensure the brakes function safely after repair.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Locate the electric brake booster/pump assembly, usually mounted near the master cylinder or under the vehicle near the brake lines. Visually inspect the wiring harness connector for the booster pump for signs of corrosion, pushed-out pins, or chafed wires rubbing against the chassis or subframe. - Step 2: Diagnostic Verification
Using a digital multimeter, probe the signal wire for Motor B’s position sensor to check for a steady reference voltage (usually 5V) while the ignition is on. If the voltage is missing or erratic, verify the ground circuit integrity. If wiring and voltage check out, the diagnosis points toward an internal sensor failure within the booster pump assembly itself. - Step 3: Resolution & Reset Process
If wiring is damaged, repair or replace the affected harness section and secure it with proper loom to prevent future chafing. If the internal sensor has failed, the entire brake booster pump assembly typically requires replacement as the sensor is usually not serviced separately. After installation, the brake system must be properly bled and the EBCM must be re-initialized/calibrated using a scan tool to clear the fault code and restore full ABS/Stability Control functionality.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake Booster Pump Assembly, Wiring Harness Connector (if needed), Bidirectional Scan Tool for calibration
- Average Component Price: $350 – $750 USD
- Estimated Labor Hours: 1.5 – 3.0 hours
- Total Estimated Budget: $450 – $1,100 USD