C004900 - C004900 Brake Fluid Level Below Normal Threshold

C004900 Brake Fluid Level Below Normal Threshold Technical Specification Document

Fault Depth Definition

DTC C004900 Brake Fluid Level Below Normal Threshold is a critical safety monitoring code for the Intelligent Power Braking System. In the vehicle hydraulic braking architecture, this fault code indicates that the Control Unit has detected the volume of brake medium within the reservoir dropping below the preset safe baseline. This code not only implies a physical abnormality in liquid level state but directly relates to the state determination of Intelligent Power Braking System Partial Function Failure. From a system logic perspective, this is an activation of the Controller's safety redundancy monitoring mechanism for execution mechanism fluid medium, indicating potential leakage risk or insufficient replenishment in the current hydraulic circuit, leading to the inability to maintain full assistance efficiency under extreme operating conditions; it serves as a warning signal for vehicle driving safety.

Common Fault Symptoms

When the control system records and confirms this fault code, the driver and onboard diagnostic interface may observe the following phenomena:

• Instrument Cluster Feedback: The brake fluid level warning light or power steering related indicator lights on the combination instrument panel may abnormally illuminate.
• System Function Limitation: The assistance function of the Intelligent Power Braking System is partially reduced, manifested as increased pedal travel or delayed braking force response.
• Dynamic Monitoring Intervention: Under specific driving conditions (e.g., high-speed emergency braking), the system may automatically limit auxiliary current output to protect the hydraulic circuit.
• Fault Light Status Retention: Even after resetting under satisfied trigger conditions, related indicator lights will illuminate again upon startup signal as long as the fault is not cleared.

Core Fault Cause Analysis

Based on the Control Unit's analysis of underlying data, this fault is usually triggered by hardware or logic component anomalies in the following three dimensions:

1. Brake Fluid Level Sensor (Hardware Component) As a key component of the perception layer, its internal float, conductive contacts, or signal generator may be damaged. When the sensor cannot accurately convert liquid level height into standard electrical signals, it causes deviation in the feedback loop. The term "sensor failure" here covers reduced sensitivity due to hardware aging or signal transmission interruption.

2. Harness or Connectors (Circuit Connection) Physical damage exists on the transmission path connecting the Control Unit and the fluid level sensor. This includes insulation layer damage caused by external crushing of the harness, excessive contact resistance due to connector oxidation, or electromagnetic interference introduced by poor shielding ground connection, all causing signal distortion and triggering the logical judgment of detected sensor output voltage inconsistent with target set value.

3. Intelligent Power Braking Controller (Logic Operation) As the decision core, abnormality may occur in the internal processing circuits or software logic of the controller. When the controller reads a voltage signal, if its internal A/D conversion circuit calibration is erroneous or the fault judgment threshold drifts, it may also falsely report this code, belonging to logic operation deviation on the control end.

Technical Monitoring & Trigger Logic

The system monitors brake fluid level in real-time dynamic monitoring through a closed-loop feedback mechanism, and its determination process strictly follows the following logical architecture:

• Monitoring Target The controller continuously monitors the analog output voltage signal from the brake fluid level sensor in real time and compares it with the target set value stored in the map calibration. The core focus is whether the signal voltage amplitude falls within a normal linear range.

• Trigger Conditions

  • Ignition Switch Placed on ON Gear: Fault monitoring is executed only after the ignition switch is turned on; this fault is not recorded when the engine or vehicle is powered on but not started.
  • Data Validity Verification: The system must ensure signal voltage stability without intermittent jumps.

• Fault Setting Conditions When the controller calculates that the difference between detected sensor output voltage and target set value exceeds the preset tolerance range, or if inconsistent status persists within an ignition cycle, the system determines abnormality. At this point, the control unit will freeze fault code logic, write the state of "Intelligent Power Braking System Partial Function Failure" into the diagnostic memory, and illuminate corresponding warning lights on the instrument panel.