AU
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.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Wheel speed sensor damaged: Internal Hall element failure, coil open circuit, or short circuit prevents signal generation or distorts the signal.
  • 2Harness wear or crushing: Long-term vibration and friction damage the harness insulation under the chassis and at the bottom of the longitudinal beam, causing a short to ground or intermittent open circuit.
  • 3Internal open circuit in the floor wiring harness: The copper conductor inside the harness is broken but the insulation remains intact. Vehicle jolts cause poor contact, resulting in an intermittent fault.
  • 4Spare part model mismatch: Replacement wheel hub unit assembly or sensor model does not match the original factory specification (e.g., missing suffix letter), causing incompatible electrical parameters or signal characteristics.
  • 5Incorrect sensor installation gap or abnormal tone ring: An excessive or insufficient sensor-to-tone ring gap, or a tone ring that is deformed, missing teeth, or contaminated produces an unreliable signal, triggering a circuit fault judgment.
What To Do
  • 1
    Use the VDS diagnostic tool to read the fault codes and freeze frame data. Check the data stream for an abnormal right rear wheel speed signal (e.g., an unreasonable value like 2252 km/h, or an excessive difference from other wheel speeds).
  • 2
    Visual inspection: Check the right rear wheel speed sensor installation. Inspect the connector for looseness, water ingress, or oxidation. Measure the sensor supply voltage (with ignition ON, voltage should be approximately 12V or 5V, depending on vehicle model).
  • 3
    Sensor inspection: Measure sensor resistance (typical standard value for magnetic induction type: 1-1.5 kΩ) or check the signal output waveform (Hall type should output a square wave signal). Compare readings with the left rear wheel to determine condition.
  • 4
    Circuit continuity check: Disconnect the ABS control unit and sensor connectors. Measure the harness resistance between them (less than 1 Ω), and measure the insulation resistance to ground/power supply (greater than 10 MΩ).
  • 5
    Dynamic wiring harness test: Wiggle and pull the sensor wiring harness (especially the floor harness section and the underside of the chassis rail) while monitoring the scan tool data stream or measuring voltage changes to check for intermittent open circuits.
  • 6
    Tone ring inspection: Raise the vehicle. Inspect the tone ring on the right rear driveshaft or wheel hub for deformation, missing teeth, cracks, contamination (such as metal filings, mud, or sand), or demagnetization.
  • 7
    Spare part verification: If replacing the part, verify the new part number matches the original factory part exactly (note suffix differences, such as HAD-3630330 and HAD-3630330A). If necessary, cross-check by swapping the left and right sensors.
  • 8
    Repair verification: After rectifying the fault, clear the DTC and perform a road test (including flat and bumpy roads) to confirm the data stream is normal, the fault lamp is off, and system function recovers.
Real-World Cases
BYD DTC AI Analysis

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

✓
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

✓
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

✓
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
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 overview →
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.