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C003B04

DTC C003B04 indicates the ABS control unit detects an electrical fault in the right rear wheel speed sensor signal circuit, including open circuit, short to ground, short to power, or abnormal signal — Atto 3

Braking System

DTC C003B04 indicates the ABS control unit detects an electrical fault in the right rear wheel speed sensor signal circuit, including open circuit, short to ground, short to power, or abnormal signal.

The wheel speed sensor (typically utilizing Hall effect or electromagnetic principles) serves as a key input component for the ABS/ESC system.

It converts wheel speed into electrical signals and transmits them to the control unit to calculate slip ratio, vehicle speed, and travel direction.

Triggering this DTC degrades or disables functions such as Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Program (ESP), and Automatic Emergency Braking (AEB).

The instrument cluster illuminates the ABS/ESC warning lamp to alert the driver.

In models such as the BYD E5, the sensor typically integrates into the wheel hub assembly and connects to the ABS control unit via the floor wiring harness.

The wiring routes through wear-prone areas like the chassis side member, frequently developing hidden faults after long-term use.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

Wiring harness chafed through to ground, causing ABS warning light to illuminate intermittently.

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BYD F3 with approximately 103,000 km. ABS warning light intermittently illuminated while driving. Live data showed right rear wheel speed at 2252 km/h (other wheels at 0). Replaced the sensor; no change. Measured wiring and found continuity to body. Found white-red wire chafed through at bottom of right side member. Taped and secured wiring. Fault cleared.
Original source ↗
BYD DTC AI Analysis

Internal break in floor wiring harness causes faults on bumpy roads

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When driving on rough roads, the dashboard displayed 'Automatic Emergency Braking function limited, please check ESP system'; flat roads normal. VDS scan showed C003B04 and other codes. Sensor voltage tested normal, but fluctuated abnormally when tugging the wiring harness. Diagnosed internal break in floor wiring harness. Replaced floor wiring harness assembly; fault resolved.
Original source ↗
BYD DTC AI Analysis

Replacement part number mismatch caused sensor failure

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ESP warning lamp on; VDS reported C003B04. Checked sensor power supply — normal. Replaced wheel hub unit assembly (including sensor); fault remained. Swapped left/right sensor harnesses; fault transferred, confirming the new part was defective. Found ordered PN was HAD-3630330, while the original vehicle had HAD-3630330A (A suffix). Installed the correct PN; fault cleared.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.