C058D

Code

Generic C — Chassis

Brake Booster Motor B Position Sensor Circuit High

Brand: Generic

Type: C — Chassis

Views: UK: 18 EN: 19 RU: 18

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Page language: EN

Causes

Open, short to voltage, or intermittent wiring/connector fault on the sensor output circuit
Corroded or poorly connected sensor connector or terminal
Failed Brake Booster Motor B position sensor
Faulty braking/booster motor control module (ABS/ECU) or its internal circuitry
External power feed leaking into the sensor circuit (backfeed)
Water intrusion or mechanical damage to sensor or harness

Symptoms

Brake assist may be reduced or ABS/brake-related warning lamp(s) illuminated
Fault is stored in the ABS/Brake control module and may cause limp or degraded mode
Possible reduced pedal feel or unexpected brake assist behavior
Intermittent or permanent warning light on dash (ABS, BRAKE, or traction control)
Fault reoccurs after cleaning or moving the harness if wiring damage is present

What to check

Read and record freeze-frame and live data for Brake Booster Motor B sensor output
Perform a visual inspection of sensor, harness, and connectors for damage, corrosion, or water
Check for related stored codes (ABS, traction, body) and recent repairs
Measure connector voltage at key ignition states (key ON, engine OFF and running if safe)
Verify good ground and reference voltage to the sensor
Wiggle harness and connectors while monitoring live data to reproduce fault

Signal parameters

Normal position sensor output typically varies across ~0.1–4.9 V depending on design; mid-position often around ~2.5 V
High fault condition: sensor output above upper threshold (commonly >4.6–4.9 V) or near battery voltage
Open-circuit can present as high or floating voltage on module input if internal pull-up/pull-down exists
Reference (Vref) often 5 V ±0.25 V; ground should be
If sensor is Hall or PWM-type, expect specified frequency/amplitude from OEM data; deviation indicates fault

Diagnostic algorithm

Obtain freeze-frame and live data. Note when the code sets and any correlated events (moisture, steering, braking).
Visually inspect the B position sensor, its connector, and wiring for damage, corrosion, or pin deformation. Repair as needed.
Unplug the sensor connector. With ignition ON (do not start), measure the sensor output pin at the connector while monitoring the control module input (use a back-probe). If the open connector still shows a high voltage at the module side, suspect wiring short to battery or module internal fault.
Measure reference voltage (Vref) and ground at the connector. Confirm Vref is within spec (approx. 5 V) and ground continuity to chassis. Repair poor ground or Vref issues.
Check continuity and shorts: between sensor output and battery positive (short to B+), between output and ground, and to the control module. Repair any short or open circuits.
If wiring checks good, swap with known-good identical sensor (if available) or bench-test sensor per OEM procedure. Replace sensor if it fails.
If sensor and wiring are good but high signal remains at module input, suspect control module internal fault. Confirm with module bench test or replacement/flash per manufacturer guidance.
After repairs, clear codes and perform functional test under conditions that previously set the code (vehicle start, brake booster actuation). Verify no recurrence and that live data returns to expected ranges.

Likely causes

Damaged or disconnected wiring at sensor connector (open or short to battery voltage)
Corroded connector pins causing poor contact or inadvertent supply connection
Failed position sensor (internal short/pull-up) on the booster motor
Control module output/input stage fault
Aftermarket equipment or recent repairs that disturbed wiring

Fault status

⚠️ Status

Brake Booster Motor B position sensor circuit reporting high voltage — position input above expected range. Inspect wiring, connector, sensor, and module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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