AU
C050300

DTC C050300 indicates a short to battery positive (B+) in the left front wheel speed sensor (WSS) power supply circuit — Seal U

Braking System

DTC C050300 indicates a short to battery positive (B+) in the left front wheel speed sensor (WSS) power supply circuit.

Normally, the IPB (Integrated Power Brake) supplies 5V or 12V to the wheel speed sensor (depending on sensor type).

A "short to battery" condition means the power supply line shorts to a vehicle constant power circuit, or the internal sensor power terminal breaks down to the signal or ground terminal.

This causes the control unit to detect an abnormally high voltage (approximately 12V battery voltage).

This prevents the IPB from correctly reading the left front wheel speed signal, triggers the safety protection mechanisms of systems such as ABS, ESP, and Automatic Emergency Braking, and disables the related functions.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged insulation on the left front wheel speed sensor wiring harness contacts body power wiring (such as the headlight power supply or horn wire), causing a short circuit.
  • 2Internal sensor power circuit breakdown causes a short circuit between the power terminal and the housing or signal wire.
  • 3Water ingress, corrosion, or bent pins at the wheel speed sensor connector causing the power supply terminal to short to an adjacent power terminal.
  • 4After a front-end accident repair, improper wiring harness routing or detached retaining clips cause the wiring harness to rub against sharp edges, resulting in damage.
  • 5IPB control unit internal power supply drive circuit fault causing abnormally high output voltage.
What To Do
  • 1
    Connect the VDS diagnostic tool, read and record the freeze frame data for DTC C050300, and confirm the vehicle speed and voltage status at the time of the fault.
  • 2
    Turn off the ignition, disconnect the left front wheel speed sensor connector, and check the connector terminals for corrosion, deformation, or signs of water ingress.
  • 3
    Turn the ignition switch to ON (do not start). Use a multimeter to measure the voltage between the sensor wiring harness connector power supply terminal and ground. A reading of 12V (battery voltage) confirms a short to power. The normal voltage is 5V or 12V (depending on vehicle configuration) and must remain stable within the sensor specification.
  • 4
    Disconnect the IPB control unit connector. Measure the continuity of the left front wheel speed sensor power supply circuit between the sensor and the IPB. Measure the insulation resistance of this circuit to the power supply (B+). The resistance must be greater than 10MΩ.
  • 5
    Check sensor body resistance. The normal range is typically 1.0-1.5 kΩ (magnetic induction type) or matches Hall sensor specifications. If resistance is abnormal, replace the sensor.
  • 6
    If the wiring harness has a short circuit, repair the damaged wiring (rewrap or replace the harness section). If the sensor is faulty, replace it with a genuine wheel speed sensor. Clear the fault code and perform a road test to confirm normal ABS operation.
Real-World Cases
BYD DTC AI Analysis

Left front wheel speed sensor harness worn through, short to power

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Vehicle: Song PLUS DMi 2022 model, 12,000 km. Symptoms: ABS and ESP warning lights constantly on; DTC C050300. Diagnosis: Lifted the vehicle and found the left front wheel speed sensor harness chafed through at the steering knuckle mounting point. The damage exposed internal copper wires that were touching the headlight power supply wire, causing a 12V short. Measured 12.5V at the sensor supply (abnormal). Fix: Soldered the damaged harness and insulated it with double-layer heat shrink tubing. Re-routed and secured the harness to prevent interference with steering components. Replaced the left front wheel speed sensor (possibly damaged by the short). Fault cleared.
BYD DTC AI Analysis

Water in the sensor connector caused a power supply short circuit.

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Vehicle: BYD Han EV. C050300 DTC set after driving through water. Found clear water staining and corrosion inside the left front wheel speed sensor connector. The power supply terminal had shorted to an adjacent constant-power terminal (possibly for the steering assist light). Cleaned and dried the connector, applied conductive grease, measured normal insulation, and cleared the fault. Recommend checking front wheel arch sealing.
BYD DTC AI Analysis

Aftermarket headlight modification damaged the wheel speed sensor wiring

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Vehicle: BYD Qin PLUS DMi. During a DIY LED headlight install, the owner secured the wiring with a clip that pierced the left front wheel speed sensor harness, shorting the sensor power feed to the headlight supply. The ABS warning light lit intermittently while driving. The scanner read C050300. Supply voltage changed with the headlight switch position. Repaired the harness and rerouted the wiring to resolve the fault.
Other Seal U Fault Codes
B1108For 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.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.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.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.
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.