AU
C050B76

DTC C050B76 indicates the IPB (Intelligent Integrated Braking System) detects a correlation fault in the right front wheel speed sensor signal — Seal U

Braking System

DTC C050B76 indicates the IPB (Intelligent Integrated Braking System) detects a correlation fault in the right front wheel speed sensor signal.

This fault does not indicate a simple signal loss (open circuit).

Instead, the sensor pulse signal output logically mismatches actual vehicle dynamics (e.g., other wheel speeds, vehicle speed, acceleration, yaw rate), or the signal characteristics (frequency, amplitude, duty cycle) exceed calibrated thresholds.

The IPB algorithm compares the correlation of all four wheel speed sensors.

The system sets this code when the right front signal differs excessively from the other wheel speeds, exhibits erratic signal jumps, or experiences an intermittent fault in the sensor power supply or ground circuit.

This fault directly affects the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Automatic Emergency Braking (AEB), and energy recovery functions.

It may increase braking distance or cause abnormal brake pedal feel.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Right front wheel speed sensor performance degradation or internal coil inter-turn short circuit causes insufficient output signal amplitude or waveform distortion. Signal quality degrades especially at high temperatures or high wheel speeds.
  • 2Abnormal air gap between the sensor and the magnetic encoder ring (tone ring) (greater than 1.2 mm or less than 0.3 mm). Common causes include a loose sensor retaining bolt, a deformed bracket, or bearing wear causing axial hub play.
  • 3Damage to the right front wheel hub unit magnetic encoder ring (demagnetization, cracking, or attached iron filings) causes uneven magnetic flux changes, generating signal noise or missing tooth signals.
  • 4Intermittent sensor wiring harness fault, including poor contact at IPB control unit connector pin 26 (signal) or pin 25 (power supply), poor contact in the body ground circuit, or wiring harness chafing and shorting during suspension movement.
  • 5Inconsistent tyre sizes or severely unbalanced tyre pressures cause the actual speed of the right front wheel to systematically deviate from the other wheels, triggering an IPB correlation check failure.
What To Do
  • 1
    Use a diagnostic tool to read freeze frame data and confirm vehicle speed, wheel speed values, and IPB supply voltage when the fault occurred. Check for accompanying fault codes (e.g., C050A00, U0121). Clear the fault codes and perform a road test. Observe if the right front wheel speed data stream spikes or is out of sync with other wheel speeds.
  • 2
    Raise the vehicle and visually inspect the right front sensor. Verify the mounting bolt torque (standard: 8-12N·m). Check the wiring harness for tension at the steering limit positions. Measure the sensor resistance (standard: 1.5-2.5kΩ at 20°C). Measure the sensor supply voltage (standard: 12V±0.5V with ignition ON).
  • 3
    Remove and inspect the right front wheel speed sensor. Use a feeler gauge to measure the radial gap between the sensor tip and the magnetic encoder ring (standard: 0.3-1.2 mm). Inspect the encoder ring surface for scratches, corrosion, or foreign matter. Clean the ring and check magnetic pole integrity (use iron filings to test magnetic distribution).
  • 4
    Monitor the sensor signal waveform using an oscilloscope. Slowly rotate the wheel and verify a regular square/sine wave. Check for spikes, flat tops, or missing pulses. Compare with the left front wheel waveform to confirm consistent amplitude and frequency.
  • 5
    If the above checks are normal, perform the IPB system calibration procedure (using the diagnostic tool, access IPB Special Functions → Wheel Speed Sensor Calibration) and verify the IPB software is the latest version (compare against the TPI technical bulletin). If the fault is intermittent, inspect pin 26 (right front wheel speed signal) of IPB harness connector X1 for looseness or oxidation.
Real-World Cases
BYD DTC AI Analysis

Worn right front bearing on Song PLUS DM-i causing excessive clearance

✓
A 2021 Song PLUS DM-i with 60,000 km intermittently illuminated the ABS and ESC warning lights on the instrument panel. The scan tool retrieved DTC C050B76. Freeze frame data showed the fault occurred at 60 km/h when the right front wheel speed signal suddenly dropped to zero. Inspection found 0.8 mm of axial play in the right front hub bearing, causing the air gap between the magnetic encoder ring and sensor to vary dynamically while driving. Replaced the right front hub assembly (including the encoder ring) and adjusted the sensor air gap to 0.6 mm. Fault resolved.
BYD DTC AI Analysis

Sensor harness chafed at steering knuckle and shorted

✓
DTC C050B76 appeared after the vehicle drove through water, accompanied by restricted Automatic Emergency Braking function. Inspection found the right front wheel speed sensor wiring harness chafed where it passes through the steering knuckle bracket, with the copper core intermittently shorting to the body. The fault showed normal operation at low speeds but signal abnormalities during high-speed cornering when the harness stretched. Repaired the damaged wiring, reinforced the insulation with heat shrink tubing, and re-secured the harness routing to prevent contact with suspension components.
BYD DTC AI Analysis

Mismatched tyre specifications caused related faults

✓
The owner replaced the right front tyre; the warning light illuminated the next day showing DTC C050B76. Inspection revealed the new tyre was size 225/55R18, while the original and other three tyres were 225/60R18, causing the right front rolling circumference to differ from the other wheels by approximately 3%. The IPB system flagged the right front sensor signal as faulty based on four-wheel speed differential logic. Fitting the correct size tyre and performing tyre pressure calibration cleared the fault.
BYD DTC AI Analysis

Oxidized IPB control unit connector caused signal drift

✓
Southern humid region vehicle. After one week parked, C050B76 triggered immediately at startup. Sensor power supply normal, but signal line voltage fluctuated between 0.5–3V (normal: 0–12V pulse). Disconnected IPB control unit connector; pin 26 (right front wheel speed signal) showed green corrosion. Cleaned connector with electronic contact cleaner, applied conductive grease, and replaced terminals as needed. Fault resolved.
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.