Code
C058B
Generic
C — Chassis
Brake Booster Motor B Position Sensor Circuit/Open
Views:
UK: 21
EN: 27
RU: 19
AI status
Completed
Completed
100%
Causes
- Open or high-resistance wiring in the sensor signal or ground circuit
- Corroded, loose, or damaged connector at the brake booster motor/sensor
- Faulty brake booster motor position sensor (Hall or potentiometer)
- Short to battery or short to ground on the sensor signal or reference circuit
- Failed brake booster motor assembly or integrated sensor module
- Faulty ABS/BRK control module (rare)
Symptoms
- Brake warning lamp or ABS warning on dash
- Reduced or intermittent power brake assist; heavier pedal feel
- Check engine/BRK/ABS lamp may set along with related faults
- Possible inconsistent brake boost or pulsation during stop/start cycles
- Stored fault code(s) and freeze frame data
What to check
- Retrieve freeze frame and live data with a scan tool; note sensor values and status
- Visually inspect connector and wiring at the brake booster motor for damage, corrosion or water
- Wiggle test wiring while observing live data for intermittent changes
- Check for other related DTCs (ABS, brake pressure, CAN communication)
- Confirm vehicle battery/charging system voltage is normal
Signal parameters
- Reference voltage (varies by manufacturer): typically ~5 V reference to the sensor (verify with service data)
- Sensor output voltage (typical Hall/pot style): ~0.5–4.5 V depending on position; should change smoothly with movement
- Open-circuit: infinite resistance / no output; short-to-ground: near 0 V; short-to-battery: near VBAT
- If PWM-type, signal frequency and duty cycle will vary with position — typical frequencies range from a few hundred Hz to several kHz (refer to OEM spec)
Diagnostic algorithm
- Connect a scan tool and confirm C058B and any related codes; record live sensor values and status.
- Visually inspect the brake booster motor connector and harness for corrosion, pin damage, chafing or water entry; repair damaged insulation and connectors as needed.
- With ignition ON (engine off), backprobe the sensor connector: verify reference voltage (typically ~5 V) and good chassis or sensor ground per OEM spec.
- Observe sensor signal while moving brake booster motor actuator (or command motor via actuator control if service tool supports it); signal voltage should change smoothly. No change indicates open/failed sensor.
- If no reference or signal, perform continuity/ resistance checks from the sensor connector back to the ABS/brake module pins to find opens or high resistance.
- Check for shorts to battery or ground by measuring voltage at the sensor harness with connector disconnected while comparing to harness pin voltage with connector connected.
- If wiring and connectors are good but sensor output incorrect, remove and bench-test or replace the brake booster motor assembly or the internal position sensor per service instructions.
- After repairs, clear codes, perform relearn/calibration if required by manufacturer, and road-test to confirm proper operation and that code does not return.
Likely causes
- Open or damaged wiring between the sensor and module
- Corroded/loose connector at the sensor or module
- Failed position sensor inside the brake booster motor assembly
- Water/dirt intrusion causing intermittent/open connection
Fault status
Status
Brake Booster Motor B Position Sensor Circuit/Open — the brake control module is not receiving a valid position signal from the booster motor B sensor (open or circuit fault).
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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