🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor A Position Sensor Supply Circuit/Open
This code is a Chassis code monitored by the Electronic Brake Control Module (EBCM), which governs the electro-hydraulic or electro-mechanical brake booster assist system. The fault indicates that the EBCM has detected an open or out-of-range condition on the reference voltage supply circuit feeding the position sensor for Brake Booster Motor ‘A’. This sensor tells the control module the precise rotational or linear position of the booster motor’s actuator, which is essential for calculating correct brake assist force. When the supply circuit is open, the module cannot receive a valid position signal, so it cannot safely command the motor to provide appropriate brake boost. This typically results in the stability control and traction control warning indicators illuminating, a noticeably harder or inconsistent brake pedal feel, and the EBCM restricting brake assist functions until the fault is cleared and verified safe.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair involves working directly within the brake booster motor assembly and its control wiring harness, which carries safety-critical functions. A digital multimeter and a bidirectional scan tool capable of reading live EBCM data and performing module resets/calibrations are required. Due to the complexity of the brake assist system and potential brake performance risks, this should be handled by a trained technician with proper safety procedures.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Visually inspect the wiring harness and connector leading to the brake booster motor position sensor for chafing, corrosion, pinched wires, or a disconnected plug. Check the harness routing near the brake booster/hydraulic unit for signs of heat damage or rodent intrusion, and verify the connector is properly seated and locked. - Step 2: Diagnostic Verification
Using a digital multimeter, verify battery reference voltage (typically 5V) is present and stable at the sensor supply circuit with the connector disconnected, then check continuity to ground for shorts. With a scan tool, monitor live position sensor data for Motor A to see if the signal is flatlined, erratic, or missing entirely, confirming an open circuit rather than an intermittent fault. - Step 3: Resolution & Reset Process
If wiring is damaged, repair or replace the affected harness section and connector terminals using proper automotive-grade splices and dielectric sealing. If the supply circuit tests correctly but the fault persists, replace the brake booster motor/position sensor assembly as a unit, since these components are typically not sold separately. After repair, use the scan tool to clear stored codes, perform any required EBCM brake booster relearn or calibration procedure, and road test while monitoring pedal feel and warning indicators.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake booster motor/position sensor assembly, wiring harness repair kit (connectors/terminals), bidirectional scan tool with EBCM calibration capability
- Average Component Price: $180 – $450 USD
- Estimated Labor Hours: 1.5 – 3.0 hours
- Total Estimated Budget: $320 – $750 USD