AU
C050A00

DTC C050A00 indicates the IPB (Intelligent Integrated Braking System) ECU detects the air gap between the right front wheel speed sensor (WSS) and the signal tone ring exceeds the calibrated tolerance range (typically 0 — Seal U

Braking System

DTC C050A00 indicates the IPB (Intelligent Integrated Braking System) ECU detects the air gap between the right front wheel speed sensor (WSS) and the signal tone ring exceeds the calibrated tolerance range (typically 0.3-1.2mm), or the sensor signal amplitude/phase exhibits intermittent erratic characteristics.

This is a plausibility fault, distinct from a direct short or open circuit.

The IPB system uses an active Hall-effect wheel speed sensor highly sensitive to the installation air gap.

An excessive gap attenuates the signal, while an insufficient gap causes the sensor head to rub against the tone ring.

The ECU sets this fault when algorithmic compensation cannot verify wheel speed signal reliability.

This fault degrades or disables ABS, ESP, TCS, and Automatic Emergency Braking (AEB) functions.

In severe cases, it illuminates the brake system warning lamp continuously.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Loose wheel speed sensor installation, or mud, sand, or foreign matter in the mounting hole, causes the actual air gap to deviate from the standard value.
  • 2Excessive axial play or wear in the right front wheel hub bearing causes axial displacement of the integrated signal tone ring (magnetic encoder ring), changing the air gap.
  • 3Bottoming out, stone strikes, or long-term wear physically damages the wheel speed sensor head, affecting the magnetic field distribution.
  • 4The tone ring (magnetic encoder ring) is deformed, damaged, or has a heavy buildup of iron filings/mud on the surface, causing signal distortion and a false air gap diagnosis.
  • 5Installed non-genuine wheel hub bearing or sensor; component dimensional tolerances do not meet IPB system accuracy requirements.
What To Do
  • 1
    Use VDS2000 or the BYD dedicated diagnostic tool to read complete fault codes, confirm if the fault is current (Present), and record freeze frame data (vehicle speed, temperature, etc.).
  • 2
    Raise the vehicle. Check the right front wheel speed sensor exterior and wiring harness connector for damage or water ingress. Check the sensor tip for wear marks or attached foreign matter.
  • 3
    Remove the right front wheel speed sensor. Use a feeler gauge or dedicated air gap measuring tool to measure the air gap between the sensor tip and the tone ring (standard value: 0.3-1.2 mm). Rotate the wheel hub one full revolution and measure at multiple points to verify the air gap is uniform.
  • 4
    Check the wheel hub bearing axial play: Grip the top and bottom of the tire with both hands and push and pull to check for obvious play. If present, replace the wheel hub bearing assembly.
  • 5
    Check the signal tone ring: Inspect the magnetic encoder ring for cracks, deformation, or missing teeth. Clean iron filings and dirt from the tone ring surface.
  • 6
    If the air gap is abnormal but the bearing and tone ring are normal, check the sensor mounting seat for deformation. Replace the sensor if necessary (some models use a sensor shim; confirm the shim is intact).
  • 7
    After installing the new sensor or bearing, remeasure the air gap to verify it is within the standard range. Tighten the sensor retaining bolt (typical torque: 8-12 N·m).
  • 8
    Clear the fault code, calibrate the wheel speed sensor (if required by the workshop manual), perform a road test (including straight-line driving and cornering), and confirm the IPB system has no abnormalities.
Real-World Cases
BYD DTC AI Analysis

Dolphin ESP false trigger: Bearing wear increased air gap

✓
Symptoms: The BYD Dolphin’s ESP warning light illuminated intermittently while driving, with a kick-back sensation through the brake pedal. Scan tool retrieved DTC C050A00 (Right Front Wheel Speed Sensor Air Gap Abnormal). Diagnosis: Raised the vehicle and inspected the right front wheel speed sensor; it appeared undamaged. Measured the sensor air gap and found a maximum of 1.8 mm (exceeding specification). The wheel bearing also showed noticeable axial play—0.5 mm of vertical movement when pushing the tire up and down. The worn hub bearing caused the integrated ABS tone ring to sink, creating an uneven air gap. Repair: Replaced the right front wheel hub bearing assembly (including the ABS tone ring). Reinstalled the OEM sensor and adjusted the air gap to 0.6 mm. Cleared the fault codes and road-tested; ESP function returned to normal.
BYD DTC AI Analysis

Signal plate deformed after Yuan Plus bottomed out

✓
Symptoms: Right front wheel struck a curb. Dashboard displayed 'Braking System Fault'. DTCs C050A00 and C003400 retrieved (right front wheel speed sensor signal fault). Diagnosis: Removed right front wheel. Found slight scrape marks on the wheel speed sensor head and localized denting on the tone ring (magnetic ring), causing periodic air gap variation during rotation. Resolution: Replaced right front wheel speed sensor and wheel hub bearing unit together (tone ring is integrated with the bearing). Set air gap to workshop manual specifications during installation. Fault resolved.
BYD DTC AI Analysis

BYD Seal intermittent fault: Silt in mounting hole causing abnormal air gap

✓
Symptoms: After driving through water, the BYD Seal's ESP warning light flashed intermittently. The scanner logged intermittent DTC C050A00. Diagnosis: Checked the sensor connector for water ingress; none found. Measured sensor resistance; normal. Removed the sensor and found heavy sediment buildup in the mounting bore preventing full seating, resulting in an air gap exceeding specification. After cleaning and reinstalling, the air gap remained slightly over the upper limit at 1.3mm. Resolution: Thoroughly cleaned the mounting seat. Installed a new sensor with adjustment shim. Used a feeler gauge to check multiple points and verified air gap within 0.3-1.2mm. Cleared the DTC; the fault has not recurred.
BYD DTC AI Analysis

Qin PLUS DM-i Aftermarket Bearing Dimensional Deviation

✓
Symptoms: Following replacement of the right front wheel hub bearing at an independent workshop, the BYD Qin PLUS DM-i showed constant ABS/ESP warning lights and set DTC C050A00. Diagnosis: Comparing the old and new bearings revealed the aftermarket unit's magnetic encoder ring position deviated approximately 0.5 mm axially from the OEM part. This left the sensor air gap too small after installation (measured at 0.2 mm), saturating the sensor signal. Solution: Installed an OEM wheel hub bearing assembly, adjusted the air gap to specification, calibrated the wheel speed sensor with a diagnostic tool, and cleared 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.