🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor B Position Sensor Circuit Range/Performance
This code is a Chassis (C) code, indicating that the diagnostic concern resides within the braking system’s electronic control architecture, specifically monitored by the Electronic Brake Control Module (EBCM) or the Power Steering/ABS control module. The code sets when the control module detects that the position sensor signal for ‘Motor B’ within the electric brake booster assembly is reporting data outside of its expected range, or the signal does not correlate logically with the commanded position during a brake apply event. Modern electro-hydraulic and electro-mechanical brake boosters use precision motors to generate brake assist pressure (replacing traditional vacuum boosters), and a secondary position sensor (Motor B) tracks the exact rotational placement of the actuator. If the sensor’s voltage output doesn’t match the expected curve relative to the motor’s commanded movement—due to mechanical binding, sensor degradation, or wiring resistance—the module flags a Range/Performance fault to protect brake assist functionality and may trigger reduced brake assist, a stability control warning, or an ABS/Brake warning lamp on the dash cluster.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires access to a bi-directional scan tool capable of actuating the brake booster motor and reading live position sensor data in real time, as well as a digital multimeter to check resistance and voltage drop across the sensor harness. Because this is a safety-critical brake assist component, any disassembly, bleeding, or recalibration must be performed by a certified technician with experience in electro-mechanical brake systems to avoid compromising brake performance.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and electrical connector leading to the brake booster motor assembly. Look for corrosion, chafed insulation, pinched wires near the pedal box, or a loose/unseated connector pin. Also inspect the booster unit itself for any signs of fluid intrusion or physical damage near the motor position sensor housing. - Step 2: Diagnostic Verification
Connect a capable scan tool to pull live data for the Motor B position sensor. Command the booster motor through its range (if bi-directional controls are supported) and compare the commanded position against the actual reported sensor voltage. Use a digital multimeter at the connector to verify reference voltage (typically 5V), ground integrity, and signal return voltage, checking for erratic readings, dropouts, or resistance exceeding manufacturer specification in the harness. - Step 3: Resolution & Reset Process
If wiring and connectors test within specification but the sensor signal remains erratic or out of range, the brake booster assembly (including the integrated Motor B position sensor) will need replacement, as these sensors are typically not sold or serviced separately from the booster unit. After installation, the system must undergo a mandatory brake booster initialization/calibration procedure using the scan tool, followed by a stability control system self-test and clearing of stored chassis codes.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Electric Brake Booster Assembly (with integrated Motor B position sensor), OEM-level bi-directional scan tool, Digital Multimeter, Brake fluid for system bleed
- Average Component Price: $350 – $750 USD
- Estimated Labor Hours: 2.5 – 4.0 hours (includes booster replacement, system bleed, and calibration)
- Total Estimated Budget: $550 – $1,150 USD