C05CE00 - C05CE00 Master Cylinder Position Sensor B Circuit Voltage Low

C05CE00 Master Cylinder Position Sensor B Circuit Low Voltage: Fault Depth Definition

In intelligent power brake system architecture, this DTC indicates that the Control Unit has detected an electrical signal anomaly in Master Cylinder Position Sensor B channel. The Master Cylinder Position Sensor acts as a physical position sensing device, responsible for collecting displacement or angular changes during driver braking pedal application in real time and converting analog physical quantities into digital pulse signals uploaded to the controller. When "B circuit" voltage is low, it indicates that the power signal on this feedback path cannot maintain a normal logic high level state, causing the control unit to be unable to accurately obtain real-time dynamic data of the pedal position, thereby affecting regenerative braking allocation or hydraulic boost adjustment functions. This DTC falls under the signal integrity monitoring category, core being determining excessive external circuit resistance or grounding short that causes voltage drop, disrupting the closed-loop feedback mechanism of the intelligent power brake system.

Common Fault Symptoms

When the system records this fault, drivers can perceive the following manifestations:

• Dashboard fault indicator lights up, displaying intelligent power brake system related warning information;
• Vehicle enters restricted protection mode, causing partial power brake assist functions to fail or run in degraded condition;
• No other direct physical feedback abnormality on dashboard, but Master Cylinder Position Sensor B channel values in background data stream show logic low level.

Core Fault Cause Analysis

The triggers of this fault can be located by technical positioning in the following three dimensions:

• Hardware Component Failure: Internal circuit damage within Master Cylinder Position Sensor B, aging of signal output terminal or power pin open circuit, resulting in inability to output normal logic levels, constituting direct failure at the physical component level;
• Wiring and Connector Issues: Open circuits in the Master Cylinder Position Sensor B supply wiring, excessively high contact resistance, or ground short (Ground Short) caused by external interference, causing voltage to be pulled below the threshold; Fuse blowout is the direct physical manifestation of this circuit protection triggering, typically indicating interruption of prior-stage power supply;
• Controller Internal Logic Failure: Damage to the internal signal processing module within the Intelligent Power Brake Controller or drift in the reference voltage source, leading the system to misjudge as low voltage input, belonging to logic computation abnormality within the control unit itself.

Technical Monitoring and Trigger Logic

The control unit determines this fault occurs based on the following logic states:

• Set Conditions: System monitors sensor circuit signals continuously when the ignition switch is in the ON position; if this condition is not met, the system typically does not store a fault record;
• Monitoring Objectives: Focused detection of Master Cylinder Position Sensor B circuit voltage signals below the preset low-voltage threshold to ensure signals remain within normal impedance ranges;
• Determination Mechanism: During brake pedal stationary or dynamic operation, if the B circuit input signal remains continuously at a low level and does not conform to normal impedance characteristics, fault recording is triggered and relevant indicators are illuminated.