AU
C050200

This DTC indicates the IPB (Intelligent Integrated Braking System) control unit detects an abnormally low-resistance connection between the left front wheel speed sensor (WSS) power supply circuit (typically a 12V DC supply) and body ground (GND), indicating a short to ground — Atto 3

Braking System

This DTC indicates the IPB (Intelligent Integrated Braking System) control unit detects an abnormally low-resistance connection between the left front wheel speed sensor (WSS) power supply circuit (typically a 12V DC supply) and body ground (GND), indicating a short to ground.

The wheel speed sensor uses a two-wire design (multiplexed power/signal or independent power and ground).

When the power supply circuit shorts to ground, the sensor fails to receive normal operating voltage.

This causes a complete loss of the left front wheel speed signal and prevents the IPB from monitoring the left front wheel speed.

This fault directly degrades or completely disables systems including the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Traction Control System (TCS), Automatic Emergency Braking (AEB), and Electronic Parking Brake (EPB).

The vehicle may enter a safety protection mode (limp mode) and brake pedal feel may change, severely compromising driving safety.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Damaged left front wheel speed sensor wiring harness insulation. Suspension movement causes the harness to rub against metal body components (such as the steering knuckle, lower control arm, or fender liner retaining screws), shorting the power wire to ground.
  • 2Internal breakdown of the wheel speed sensor drive circuit (e.g., shorted Zener diode or filter capacitor), shorting the power supply pin to the housing (ground).
  • 3Wheel speed sensor connector seal failure (seal ring aging or improperly installed); water or electrolyte ingress causes a short circuit between the power pin and ground pin.
  • 4Breakdown of the MOSFET or related protection component in the IPB control unit internal power supply drive circuit for the left front wheel speed sensor causes the output terminal to short to ground.
  • 5During vehicle modifications (such as installing fender liners or sound insulation) or accident repairs, retaining screws crush, clips pinch, or hole edges cut the wiring harness, damaging the insulation.
What To Do
  • 1
    Visual inspection: Raise the vehicle, remove the left front wheel, and check the routing of the wheel speed sensor wiring harness near the fender liner, suspension spring seat, steering knuckle, and lower control arm. Inspect the harness for wear, damaged insulation, pinching, or burn marks. Inspect the connector for looseness, water ingress, corrosion, or backed-out pins.
  • 2
    Voltage measurement: Disconnect the left front wheel speed sensor connector, turn the ignition switch to ON, and measure the voltage between the harness-side power supply pin and ground. Normal voltage is 12V (battery voltage). A reading of 0V or very low (<1V) indicates a short circuit in the wiring harness or at the IPB end. A normal reading indicates a possible internal short to ground in the sensor.
  • 3
    Resistance measurement: Turn off the ignition switch and disconnect the IPB control unit connector (or wheel speed sensor connector). Use a multimeter to measure the resistance between the left front wheel speed sensor power supply circuit and body ground. Normal resistance is greater than 10MΩ (infinite). If the resistance is less than 1Ω or continuity exists on the buzzer setting, confirm a short to ground.
  • 4
    Section-by-section fault tracing: If confirming a wiring harness short circuit, use the section-by-section measurement method (progressively peel back the harness sheath or disconnect intermediate connectors from the sensor end toward the IPB end) to pinpoint the short circuit location. Focus inspection on areas where the harness passes through body openings, retaining clips, moving suspension components, and the section running parallel to the front wheel brake hose.
  • 5
    Component isolation check: If the entire wiring harness measures normal (infinite resistance to ground), replace the left front wheel speed sensor and test. If the fault persists, reconnect the wiring harness and measure the resistance to ground at the corresponding output pin of the IPB control unit. Continuity indicates an internal short circuit in the IPB; replace the IPB assembly.
  • 6
    Repair verification: After repairing the wiring harness (re-wrapping with insulating tape or heat shrink tubing, or replacing the wiring harness assembly) or replacing the component, restore all connections. Clear the fault code using the diagnostic tool. Perform a wheel speed sensor signal consistency check (read the data stream to confirm the left front wheel speed signal changes synchronously with the right front and rear wheel speeds during driving). Road test the vehicle to confirm the ABS/ESC warning lamp turns off and the system functions normally.
Real-World Cases
BYD DTC AI Analysis

Song Plus DMi left front wheel speed sensor harness rubbing against suspension causing C050200

✓
While driving on rough roads, the ABS and ESC warning lights occasionally illuminated on the dash, clearing after an ignition cycle. The scanner retrieved DTC C050200, with freeze frame data showing the fault occurred at approximately 30km/h. Raised the vehicle and found the left front wheel speed sensor wiring harness had come loose from its retaining clip near the lower control arm, allowing the harness to rub against the suspension spring seat. Long-term chafing wore through the insulation, exposing the copper strands of the power wire and causing an intermittent short to ground. Repaired the damaged section by re-soldering the wires and insulating with heat shrink tubing. Re-routed and secured the harness, ensuring minimum 20mm clearance from all moving parts. Replaced the cable ties and protective sleeving. Fault eliminated.
BYD DTC AI Analysis

Internal circuit breakdown in the left front wheel speed sensor caused a short to power.

✓
After washing the vehicle, C050200 set immediately at startup and would not clear; the brake system warning light stayed on constantly. Disconnected the left front wheel speed sensor connector and measured 12V at the harness side, confirming normal IPB supply voltage. However, measuring between the sensor body pins and housing showed 0.3Ω between the supply pin and metal housing—an internal short to ground. Replaced the genuine left front wheel speed sensor (part number must match the IPB system version), cleared the fault codes, performed wheel speed sensor static calibration (Steering Angle Sensor and WSS Zero Calibration), and road-tested to confirm the repair. The sensor seal failed, allowing moisture into the internal circuit board and causing the power management chip to fail.
BYD DTC AI Analysis

Left front wheel speed sensor connector short circuit due to water ingress during rainy season

✓
After continuous heavy rain, the dashboard displayed a 'Brake System Fault' warning. Read DTC C050200. Inspection found water and green corrosion inside the left front wheel speed sensor connector, causing the power terminal to short to the ground housing and adjacent signal terminal. The connector seal had deteriorated and was missing, allowing water to splash in while driving through standing water. Cleaned the male and female terminals with electrical contact cleaner, sanded off the oxidation layer, replaced the waterproof seal, and applied insulating silicone grease at the connector mating surface to prevent further water ingress. Repaired the damaged corrugated tubing on the wiring harness to ensure waterproofing. Fault resolved.
BYD DTC AI Analysis

Internal drive circuit fault in IPB integrated brake unit

✓
PDI inspection on a new vehicle revealed DTC C050200; the code would not clear and the vehicle had not been driven. The left front wheel speed sensor harness showed no visible damage. At the sensor connector, the power supply line measured 0 Ω to earth (short circuit). They disconnected the 40-pin connector between the IPB control unit and harness and measured both sides: harness side pin 39 (left front WSS power supply) showed infinite resistance to earth (normal), while pin 39 on the IPB side showed continuity to earth. This indicated an internal short to earth in the IPB left front wheel speed sensor power supply drive circuit, likely from a production batch component defect. They replaced the IPB assembly (Intelligent Power Brake integrated braking unit), bled the system, calibrated the wheel speed sensor and longitudinal acceleration sensor, and cleared the fault.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.