Code
C058A
Generic
C — Chassis
Brake Booster Motor A Position Sensor Circuit Range/Performance
Views:
UK: 14
EN: 26
RU: 20
AI status
Completed
Completed
100%
Causes
- Faulty Brake Booster Motor A position sensor (encoder/potentiometer/Hall sensor)
- Damaged or corroded wiring/connectors between sensor and control module
- Open, short to ground, or short to battery in the sensor circuit
- Incorrect reference voltage or poor ground at the sensor
- Contaminated or mechanically binding brake booster actuator affecting sensor movement
- Faulty brake booster control module or ECU input circuit
Symptoms
- Brake assist reduced or unavailable (hard brake pedal)
- Brake warning lamp or ABS/ESP warning illuminated
- Diagnostic trouble code C058A stored
- Inconsistent or erratic brake feel or pedal travel
- Possible limp/reduced functionality of brake-assist system
What to check
- Scan for stored DTCs and capture freeze frame and live data
- Visually inspect sensor connector and wiring for damage, corrosion, or water intrusion
- Check harness routing for chafing against sharp edges or heat sources
- Verify connector terminals are fully seated and locked
- Measure reference voltage and ground at sensor connector with ignition on
- Observe sensor output while operating booster or actuating pedal (with safe, controlled method)
Signal parameters
- Reference voltage commonly 5 V (check OEM spec)
- Sensor output typical range: ~0.5–4.5 V or 0–5 V depending on sensor type
- Output may be PWM or analog — duty cycle 0–100% for PWM style
- Circuit resistance: not applicable for active Hall encoders; check OEM values if available
- Signal should change smoothly and proportionally with actuator/pedal movement
Diagnostic algorithm
- Connect a diagnostic scanner, read all fault codes and freeze frame data. Note related brakes/ECU codes.
- Perform a visual inspection: unplug the booster sensor connector, inspect pins for corrosion, bent or pushed-back terminals, and inspect wiring for damage.
- With ignition ON (engine off unless specified by OEM), measure sensor reference voltage and ground at the connector. Compare to OEM spec (typically ~5 V reference and solid ground).
- Backprobe the sensor signal wire and monitor signal while slowly actuating the brake pedal or commanding actuator per OEM service procedure. Confirm the signal changes smoothly across full travel and stays within expected voltage/duty-cycle range.
- If signal is missing, stuck, or out of range, perform a continuity and short-to-power/ground check between sensor and control module harness pins (with battery disconnected for continuity tests).
- Wiggle the harness and connector while monitoring the signal to detect intermittent faults. Check for related codes that may indicate harness or module issues.
- If wiring, reference voltage, and ground are good but signal is faulty, replace the Brake Booster Motor A position sensor or the booster assembly per OEM instructions.
- If sensor replacement does not restore proper signal, inspect and test the brake booster control module / ECU input circuit. Consider module replacement or repair if diagnostics point to internal faults.
- After repairs, clear codes and perform functional test and road test to verify correct operation and that the code does not return.
Likely causes
- Connector corrosion or loose terminal at the booster sensor
- Broken or chafed wiring in harness near booster or engine bay
- Failed position sensor inside the booster assembly
- Missing or low reference voltage (5V) or bad ground at sensor
Fault status
Status
Control module detected Brake Booster Motor A position sensor signal out of range or not performing. Fault logged and brake assist may be limited until corrected.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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