C003B00 - C003B00 Right Rear Wheel Speed Sensor Supply Voltage Low

Fault Depth Definition

DTC C003B00 (Right Rear Wheel Speed Sensor Supply Voltage Low) is a critical diagnostic fault code within an intelligent power braking system, with its core being the real-time assessment of the sensor terminal's supply state by the control unit. Within the vehicle's feedback loop, the right rear wheel speed sensor acts as a key data acquisition component, requiring stable excitation power to generate pulse signals used for real-time feedback of motor rotation speed and physical position. The triggering of this fault code indicates that the system detected electrical parameters supplied to the sensor deviating from normal standards, resulting in an unduly low voltage level. This implies not only abnormal energy transmission at the hardware level but also potentially directly diminishing the control unit's analysis accuracy for wheel speed data, thereby affecting the normal operating status of anti-lock braking logic (ABS) or Electronic Brake Force Distribution (EBD) systems.

Common Fault Symptoms

After the control unit identifies the aforementioned voltage anomaly, the vehicle enters a protective operation mode. Specific perceptible driving feedback includes:

• Brake System Warning Light Illuminated: The intelligent power braking system warning light or ABS light on the instrument cluster remains constantly lit.
• Degraded Function Operation: Some auxiliary functions of the intelligent power braking system (e.g., traction control) may become ineffective, preventing the vehicle from fully exerting its active safety performance.
• Fault Storage: Fault code C003B00 will be permanently recorded in the onboard diagnostic system until the corresponding reset operation is completed.

Core Fault Cause Analysis

Based on current system architecture, the root causes leading to low supply voltage are mainly concentrated in the following three technical dimensions:

• Line/Connector Physical Connection Anomalies: The wiring harness from the controller extending to the right rear wheel speed sensor may experience open circuits, insulation layer damage, or excessive contact resistance; connector terminals oxidized, loose, or pins recessed due to poor connection prevent current transmission and produce significant voltage drop.
• Hardware Component Internal Performance Degradation: The coil winding inside the right rear wheel speed sensor itself is damaged, or the power supply pin internal circuit is open, preventing it from maintaining normal working levels under standard power input.
• Controller Logic Operation and Voltage Regulation Anomalies: The power management module inside the intelligent power braking controller fails, unable to provide stable voltage excitation to the output end, resulting in a sensor supply voltage reading below the threshold lower limit.

Technical Monitoring and Trigger Logic

The judgment of this fault code follows strict Electronic Control Unit (ECU) self-check protocols, with its working logic as follows:

• Monitoring Target: The system continuously monitors the instantaneous voltage level on the power pin connected to the right rear wheel speed sensor in real-time.
• Trigger Condition: When the driver places the start switch into the ON position, the entire vehicle electrical system activates, and the control unit enters active diagnostic mode.
• Judgment Condition: In the ignition ON state, if the control unit detects that the voltage value supplied to the sensor remains continuously below the preset normal operating range threshold, the system will immediately mark this state as "low supply voltage" and record DTC C003B00. This monitoring process covers both vehicle stationary and driving phases, ensuring protection of sensor signal integrity even under dynamic conditions.