C05BE

Code

Generic C — Chassis

Brake Booster Motor B Position Sensor Supply Circuit High

Brand: Generic

Type: C — Chassis

Views: UK: 27 EN: 35 RU: 29

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Short to battery voltage on the sensor supply circuit
Failed Brake Booster Motor B position sensor (internal short or internal regulator failure)
Poor or corroded connector or pin that is causing intermittent/high voltage readings
Faulty wiring (chafed insulation, pinched, or damaged conductor) allowing a high-voltage feed
Faulty control module / ECU driving the sensor supply (internal regulator or driver failure)
Aftermarket modifications or jump-start wiring error

Symptoms

Brake system warning light or ABS/ESC lamp illuminated
Reduced or altered brake boost behavior or degraded assist
Brake booster motor may not operate or operates unpredictably
Stored DTC(s) related to brake booster/position sensor
Possible limp or reduced-function braking mode

What to check

Retrieve freeze frame and live data with a scan tool; note battery voltage and sensor supply voltage
Visually inspect harness and connectors for damage, corrosion, or loose terminals at the sensor and module
Measure voltage at the sensor supply pin with key ON (engine OFF) and compare to vehicle reference (nominal 5 V)
Check for a short to battery on the supply wire (back-probe and compare to battery voltage)
Verify good ground(s) related to the booster and module
Perform wiggle tests while monitoring supply voltage to reproduce fault

Signal parameters

Nominal sensor supply voltage: typically approximately 5.0 V (varies by manufacturer)
High/suspect condition: supply voltage significantly above nominal (commonly >5.5 V) or equal to battery voltage
Sensor signal output: position sensor normally sends 0–5 V proportional to position (verify with live data)
Expected behavior: supply stable with key ON/engine OFF and not tied to ignition-switched battery voltage when not intended

Diagnostic algorithm

Safety: Park vehicle on level, engage parking brake, turn ignition OFF. If performing live-voltage tests, follow manufacturer safety and battery disconnect procedures as needed.
Scan for codes and record freeze-frame/live data. Note battery voltage and supply/signal values for the affected sensor.
Visually inspect the sensor connector and wiring for damage, corrosion, bent pins, or water ingress. Repair or replace damaged connectors as needed.
With ignition ON (engine OFF), back-probe the sensor supply pin and measure voltage. If voltage is at or near battery voltage, suspect a short to battery on the supply circuit.
If supply is high, isolate the sensor: disconnect the sensor connector and re-measure the supply at the harness side. If the harness side is still high, suspect wiring/ECU. If it drops to nominal with sensor disconnected, suspect the sensor.
Check continuity between the sensor supply pin and the control module supply output. Look for low resistance to battery + (short) or unexpected connections.
Verify ground(s) for the module and booster are clean and low resistance to chassis/battery negative.
If wiring and connectors test good, scan and consider bench testing or replacing the sensor. If a replacement sensor clears the fault, retest. If fault persists, investigate/reprogram/replace control module per manufacturer procedures.
After repairs, clear codes and perform road or functional test while monitoring live data to ensure correct supply and signal behavior and that the DTC does not return.