Code
C058E
Generic
C — Chassis
Brake Booster Motor B Position Sensor Circuit Range/Performance
Views:
UK: 21
EN: 23
RU: 20
AI status
Completed
Completed
100%
Causes
- Open or short in the sensor signal/return wiring
- Poor or corroded connector or pin contact at the sensor or control module
- Faulty Brake Booster Motor B position sensor (internal failure)
- Contaminated or mechanically binding booster/motor preventing correct sensor movement
- Low or intermittent sensor reference voltage or ground
- Faulty body/brake control module or software/calibration fault
Symptoms
- Brake warning lamp or ABS/Brake system lamp illuminated
- Increased or inconsistent brake pedal travel or a change in pedal feel
- Reduced or intermittent brake assist (longer pedal effort) on vehicles with electric booster
- Diagnostic Trouble Code present on scan and freeze-frame data showing abnormal sensor values
- Possible limp mode for brake assist on some vehicles
What to check
- Visual inspection of brake booster, harness, and connectors for damage, corrosion, or water ingress
- Use a scan tool to read freeze frame and live data for booster position sensors (A/B/C) while operating the brake pedal
- Backprobe sensor connector: check for reference voltage (commonly 5 V), signal voltage, and ground continuity to the module
- Wiggle test harness and observe live data for intermittent changes
- Check battery voltage and charging system while testing — low voltage can affect sensor behavior
- Inspect for mechanical binding of the booster drive/motor while commanded or manually moved (follow safety procedures)
Signal parameters
- Typical sensor reference: 5.0 V (verify with factory specification)
- Typical signal range: ~0.5–4.5 V (varies by manufacturer) — sensor should vary smoothly with pedal/booster movement
- Signal ground: continuity to chassis ground and control module ground required
- No high-frequency noise spikes; signal should be steady or smoothly varying during movement
- Exact voltages, resistances and waveforms: consult vehicle manufacturer specification sheet
Diagnostic algorithm
- Read and record all stored codes and freeze-frame data with a capable scan tool. Note related codes (ABS, brake control module).
- Visual inspection: check connectors, wiring harness, and booster for physical damage, loose pins, moisture or corrosion. Repair any obvious damage.
- With key on (engine off unless specified), backprobe the position sensor connector: verify reference voltage, signal voltage and ground continuity against manufacturer values. Record readings.
- With scan tool monitoring live data, slowly operate the brake pedal (or use diagnostic actuator if available) and observe Channel B signal. Sensor output should change smoothly and correlate with Channel A or expected movement. Look for dropouts, jumps, or stuck values.
- Wiggle wiring and connectors while observing live data to find intermittent faults. Check connector pins for corrosion/loose fit — repair or replace connectors as needed.
- If reference or ground missing/incorrect, trace wiring back to the control module and repair short/open/poor ground. Verify power supply and fuses for booster control circuit.
- If wiring and connectors are good but signal is out of range or non-correlating, replace the position sensor (or the booster/motor assembly if sensor is integral).
- After repair, clear codes, perform any required relearn or calibration procedures for the brake booster per manufacturer, then road test and re-scan.
- If fault persists after component replacement, test or replace the brake control module and verify software level/updates with the factory tool. Follow high-voltage safety procedures where applicable.
Likely causes
- Faulty position sensor in the electric brake booster (most likely)
- Damaged harness or pin-to-pin fault at the booster connector
- Corrosion or poor mating at connector terminals
- Mechanical interference in booster/motor assembly causing sensor to read out-of-range
- Faulty or missing 5 V reference or ground from control module
Fault status
Status
Brake Booster Motor B Position Sensor Circuit — signal out of expected range or performance inconsistent with commanded booster position.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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