🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor B Position Sensor Supply Circuit/Open
This is a chassis-related diagnostic trouble code monitored by the Electronic Brake Control Module (EBCM), which oversees the electric brake booster assembly. The code indicates that the EBCM has detected an open circuit or loss of reference voltage supply to the Position Sensor ‘B’ associated with the brake booster motor. This sensor is responsible for providing real-time feedback on the position of the booster’s actuator motor, allowing the EBCM to precisely modulate brake assist force. When the supply circuit to this sensor is interrupted—due to a severed wire, corroded connector pin, or internal sensor failure—the module loses the ability to accurately verify motor positioning. As a safety precaution, the system will likely reduce brake assist (resulting in a firmer pedal feel), illuminate the brake warning indicator, and may disable certain traction control or stability control functions until the fault is cleared.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair involves diagnosing and potentially replacing a safety-critical braking component within the electric brake booster assembly, which often requires specialized bi-directional scan tools capable of communicating with the EBCM. A digital multimeter is necessary to verify sensor supply voltage and circuit continuity, but due to the complexity of the booster unit and the need for post-repair system bleeding/calibration, this job should be performed by a qualified technician with proper brake system training.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and connector leading to the brake booster motor assembly, typically located near the master cylinder. Look for signs of chafed insulation, corrosion at the connector terminals, or any pinched wiring that could cause an open circuit. Also check the EBCM harness connector for bent or pushed-out pins. - Step 2: Diagnostic Verification
Using a scan tool, pull up live data for the brake booster position sensor circuits to check for an active or intermittent open condition. With the key off and harness disconnected, use a digital multimeter to check for proper reference voltage (typically 5V) at the sensor connector, and perform a continuity test across the supply wire back to the EBCM to confirm there is no break in the circuit. - Step 3: Resolution & Reset Process
If a wiring fault or corroded connector is found, repair or replace the affected harness section and connector. If the supply circuit tests normal but voltage is still not reaching the sensor, the position sensor itself (often integrated into the booster motor assembly) will need replacement. After repairs, clear the stored code with a scan tool, cycle the ignition, and verify the sensor data returns to normal operating parameters. A brake system bleed and booster calibration procedure may be required per manufacturer specifications.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake booster motor/position sensor assembly, wiring harness repair kit or connector, bi-directional scan tool with brake system access
- Average Component Price: $150 – $450 USD
- Estimated Labor Hours: 1.5 – 3.0 hours
- Total Estimated Budget: $300 – $750 USD