🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Motor B Current Sensor Circuit Range/Performance
This code is set by the Electronic Brake Control Module (EBCM) when it detects that the current sensor monitoring Motor B within the electro-hydraulic brake booster pump assembly is reporting a value outside of the expected operating range. Many modern brake booster units use dual-motor or dual-winding pump assemblies to generate the hydraulic pressure needed for brake assist, since traditional vacuum-based boosters are not used in these systems. The EBCM continuously monitors the current draw of Motor B to confirm that the pump is working efficiently and generating appropriate pressure during brake apply events, panel pre-charging, or automated braking interventions tied to the stability control and traction control systems. When the measured current deviates from the calibrated range — either too high, too low, or erratic — the EBCM flags this as a performance fault rather than a simple open/short circuit fault. This typically points to a partially degraded motor winding, a failing current sensor inside the booster pump control circuit, corrosion at the connector terminals, or a wiring harness issue causing resistance changes. Because this fault affects the brake booster module’s ability to generate assist pressure, it can also trigger an illuminated ABS or Brake Warning Indicator in the instrument cluster.
🚨 Repair Difficulty Tier
- Difficulty Rating: Professional Only
This repair requires a bidirectional scan tool capable of accessing EBCM-specific current and voltage parameters, as well as the ability to command the brake booster pump motor during active testing. Due to the safety-critical nature of the brake hydraulic system and the need for specialized bleeding and calibration procedures after replacement, this is not recommended as a DIY repair.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness and connector pins leading to the brake booster pump assembly, checking for corrosion, bent pins, chafed insulation, or signs of moisture intrusion. Confirm the integrity of the ground strap connections near the booster pump housing, as poor grounding is a common contributor to current sensor performance faults. - Step 2: Diagnostic Verification
Using a capable scan tool, access live data parameters for Motor B current draw while commanding the pump through a bidirectional test routine. Compare the observed current readings against the manufacturer’s specified range at idle and under simulated brake apply conditions. Follow up with a digital multimeter to check resistance across the motor windings and verify voltage drop across the current sensor circuit to isolate whether the fault lies in the sensor itself or the motor assembly. - Step 3: Resolution & Reset Process
If testing confirms a failed current sensor or degraded motor winding, replace the brake booster pump motor assembly (often serviced as a complete unit with the EBCM housing depending on platform). After installation, perform a full brake system bleed using the scan tool’s automated bleed procedure to purge air introduced during the pump replacement, then clear the stored fault code and complete a brake system relearn or calibration cycle as specified by the EBCM software.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake Booster Pump/Motor Assembly, OEM-level bidirectional scan tool, digital multimeter, brake fluid (DOT 3/4 as specified)
- Average Component Price: $350 – $950 USD
- Estimated Labor Hours: 2.5 – 4.5 hours
- Total Estimated Budget: $550 – $1,450 USD