AU
C050576

This DTC indicates the IPB (Integrated Intelligent Braking System) detects a correlation plausibility fault in the left front wheel speed sensor signal — Atto 8

Braking System

This DTC indicates the IPB (Integrated Intelligent Braking System) detects a correlation plausibility fault in the left front wheel speed sensor signal.

Specifically, the frequency or amplitude of the sensor pulse signal logically conflicts with the actual vehicle motion state, the other three wheel speed signals, or the longitudinal acceleration sensor data, failing the system plausibility check algorithm.

This fault typically indicates intermittent sensor signal interruption, electromagnetic interference, magnetic ring (magnetic encoder) demagnetization, or out-of-tolerance mechanical installation clearance.

These conditions prevent the ABS/ESC from accurately identifying the actual left front wheel speed, triggering the ABS warning light and ESC OFF light, and degrading the automatic emergency braking system.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Open or short circuit in the internal coil of the front left wheel speed sensor (magnetic induction type), or Hall element signal drift, resulting in unstable output signal amplitude.
  • 2Deformed sensor mounting bracket, loose retaining bolts, or missing washer causes the air gap between the sensor and magnetic ring to exceed the standard range (0.3-1.2 mm).
  • 3Heavy iron filings or mud accumulate on the surface of the wheel hub bearing magnetic encoder (magnetic ring), or the encoder has physical damage or demagnetization.
  • 4Sensor wiring harness insulation worn through at a suspension movement interference point, or oxidation or looseness at IPB control unit connector terminals B05/B06 interrupts signal transmission.
  • 5Mismatched tyre sizes (e.g., fitting a non-full-size spare tyre) or severely low left front tyre pressure causes the wheel speed difference to continuously exceed the system calibration threshold.
What To Do
  • 1
    Connect the VDS2000/VDS3100 diagnostic tool and read the C050576 freeze frame data. Record the vehicle speed, left front wheel speed, steering wheel angle, and longitudinal acceleration at the time of the fault. Check for other accompanying sub-codes in the C050500-C050599 series.
  • 2
    Raise the vehicle until the wheels are off the ground. Visually inspect the left front wheel speed sensor wiring harness for wear or stretching at the steering knuckle and lower control arm retaining clips. Inspect the connector waterproof sealing ring for aging.
  • 3
    Remove the left front wheel speed sensor and use a multimeter to measure the sensor resistance: the standard value for the magnetic induction type is 1.0-1.5 kΩ (20°C); for the Hall type, check the supply voltage (12V/5V) and signal output. Inspect the sensor tip for metal debris.
  • 4
    Clean the magnetic encoder surface. Check the magnetic ring for cracks, missing teeth, or demagnetization (use a gauss meter to measure the magnetic field strength). Check if the wheel hub bearing axial/radial play exceeds specifications.
  • 5
    Use a feeler gauge to measure the installation gap between the sensor and the magnetic ring. If the gap exceeds 1.2 mm, replace the mounting bracket or adjust the shims. Reinstall the sensor and tighten to the specified torque (usually 8-12 N·m).
  • 6
    Perform a dynamic test: Shift to D and slowly rotate the wheels. Read the data stream to verify the left front wheel speed signal synchronizes with the other wheel speeds without spikes. Perform a road test to verify ABS/ESC function recovery, then clear the fault code.
  • 7
    If the above checks are normal, measure continuity and insulation between the IPB control unit terminals and the sensor wiring harness. If necessary, update the IPB software to the latest version or replace the IPB assembly.
Real-World Cases
BYD DTC AI Analysis

Worn sensor wiring harness causing intermittent fault — Song PLUS DM-i

✓
ABS warning light illuminated intermittently when driving on rough roads. Scan tool read C050576 as an intermittent fault. Inspection revealed the left front wheel speed sensor wiring harness had chafed through the insulation at the lower control arm mounting point, causing the copper conductors to intermittently short to ground. Repaired the damaged harness, rerouted the wiring with corrugated tube protection, and secured it with cable ties clear of moving parts. Fault resolved.
BYD DTC AI Analysis

Metal debris on reluctor ring surface caused erratic signal

✓
The owner reported premature ABS activation during braking. Inspection found the left front wheel hub magnetic encoder had accumulated significant brake dust and metallic road debris, causing wheel speed sensor signal amplitude fluctuations. Cleaned the magnetic ring and test drove, but fault codes still appeared intermittently. Further inspection revealed the sensor tip was worn. Replaced the left front wheel speed sensor and thoroughly cleaned the magnetic ring. Fault resolved.
BYD DTC AI Analysis

Excessive wheel bearing play caused the reluctor ring to scrape

✓
The ESC warning light suddenly illuminated at highway speed. Live data revealed the left front wheel speed signal intermittently dropping to zero. Disassembly revealed the left front wheel hub bearing radial clearance exceeded specifications (>0.1 mm), causing dynamic interference between the magnetic ring and sensor. The sensor tip was scratched. Replaced the left front wheel hub bearing assembly (including magnetic ring) and wheel speed sensor. Fault eliminated.
BYD DTC AI Analysis

Non-full-size spare tyre caused wheel speed variance to exceed limits

✓
Replaced the left front tyre with a space-saver spare and drove. Multiple system warnings lit up on the dash. Scanner logged C050576 rationality fault. Found the spare diameter ~6% smaller than the standard tyre, causing the left front wheel speed to read consistently higher than the others. Fitted a standard-spec tyre, adjusted pressure to 2.5 bar, cleared the fault codes. System returned to normal.
BYD DTC AI Analysis

IPB software calibration error caused false alarm.

✓
During new vehicle PDI, found active fault C050576. Sensor and wiring harness checked normal; signal waveform standard. Technical service bulletin revealed IPB software V1.2 on this batch has an overly sensitive wheel speed rationality algorithm. Upgraded IPB control unit software to V1.5, performed sensor calibration, and eliminated the fault.
Other Atto 8 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.