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C024501

DTC C024501 indicates a general Wheel Speed Sensor Fault in the BYD ABS/ESP system — Seal U

Braking System

DTC C024501 indicates a general Wheel Speed Sensor Fault in the BYD ABS/ESP system.

The ABS control unit (ECU) sets this code when it detects an abnormal or completely lost wheel speed signal from at least one wheel while the vehicle is moving.

Specifically, the ECU triggers this DTC if the vehicle speed exceeds 2 km/h and the ECU fails to receive a pulse signal from a wheel speed sensor, or if the speed difference between the affected wheel and the opposite wheel on the same axle (or the reference vehicle speed) exceeds the set threshold (typically 6%) for longer than the specified time (typically 500 ms).

This fault forces the Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Electronic Stability Program (ESP), Traction Control System (TCS), Auto Hold, and energy recovery systems into a degraded or inoperative mode.

This severely compromises braking safety and driving stability.

This DTC represents a circuit or signal fault and does not involve a mechanical actuator.

However, mechanical or electrical issues with the sensor body, wiring harness, connector, or signal tone ring can cause the fault.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Wheel speed sensor internal fault: Hall element aging or failure, internal coil open/short circuit, physical damage to the sensor tip, or magnetic degradation, preventing the generation of a valid wheel speed pulse signal.
  • 2Wiring harness and connector issues: Sensor wiring harness insulation chafes due to chassis vibration, causing a short to ground or intermittent open circuit; connector pins oxidize, loosen, or back out; or water ingress after wading causes corrosion and increases contact resistance.
  • 3Abnormal signal tone ring: Missing teeth, broken or deformed tone ring (e.g., after an impact), or iron filings, mud, sand, ice, or snow adhering to the tone ring surface, altering magnetic flux and disrupting sensor signal acquisition.
  • 4Installation gap out of tolerance: A loose sensor retaining bolt or failure to apply the specified torque (usually 10 N·m) during repairs causes an excessive air gap between the sensor and the tone ring (exceeding the 1.2 mm standard), resulting in insufficient signal strength.
  • 5Inconsistent tyre specifications: Excessive tread depth difference between tyres on the same axle, severely mismatched tyre pressures, or the installation of non-OEM specification tyres causes the actual wheel speed difference to exceed the system calibration threshold, leading the ECU to misdiagnose a sensor fault.
What To Do
  • 1
    Fault confirmation and localization: Use VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Check if a specific wheel sub-fault code (such as C003708) accompanies C024501. Enter live data stream mode and drive at 10-30 km/h. Observe the four wheel speed signals to identify the abnormal wheel signal (showing 0 km/h, erratic, or differing excessively from the other wheels).
  • 2
    Visual and connection inspection: Raise the vehicle. Inspect the affected wheel speed sensor connector for looseness, oxidation, or water ingress. Trace the sensor wiring harness routing and inspect for wear, damaged insulation, or interference with the vehicle body. Focus the inspection on the harness protection where it passes through sheet metal holes and moving suspension parts.
  • 3
    Sensor electrical measurement: Disconnect the sensor connector and measure the sensor body resistance (magnetic type standard is usually 1.0-1.5kΩ; for Hall type, apply power before measuring signal voltage). Check the connector supply voltage (should be 12V±0.5V) and ground wire continuity. Use an oscilloscope to test the signal waveform and verify a stable square-wave or sine-wave output.
  • 4
    Mechanical component inspection: Inspect the sensor head for attached iron filings or physical damage. Inspect the tone ring for missing teeth, cracks, or deformation, and clean any foreign matter from the tone ring surface. Measure the gap between the sensor and the tone ring using a feeler gauge (standard is usually 0.3-1.2 mm), and check the sensor retaining bolt for looseness.
  • 5
    Repair and replacement: Based on inspection results, replace the damaged sensor, repair the damaged wiring harness (seal with heat-shrink tubing after soldering and protect with corrugated conduit), and replace the deformed tone ring or bearing assembly. Verify the sensor installation gap meets the standard, secure the connector, and apply conductive grease.
  • 6
    System verification: Clear all fault codes and perform a road test. Drive in a straight line at 30-60 km/h for at least 7 seconds and perform multiple braking tests to confirm normal ABS operation. Verify the four wheel speeds in the data stream are consistent. Confirm the fault code does not return and the instrument cluster warning light is off.
Real-World Cases
BYD DTC AI Analysis

BYD Qin left rear wheel speed sensor open circuit fault

✓
Symptoms: ABS warning light on constantly, dashboard displays 'Check ABS System', ESP function restricted. Diagnosis: VDS retrieved fault code C024501, data stream shows left rear wheel speed at 0km/h. Found left rear wheel speed sensor connector loose with oxidised pins; measured sensor resistance as infinite (internal open circuit). Solution: Replaced left rear wheel speed sensor, cleaned connector oxidation, cleared fault codes and road tested. ABS function returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Song wheel speed sensor wiring harness chafed and shorted

✓
Symptoms: While driving, the instrument cluster suddenly displayed multiple system warnings: 'Check engine system', 'ABS system', 'network', and 'braking system'. The ABS and brake warning lights lit up simultaneously. Diagnosis: VDS scan retrieved DTCs C024501 and C003708 (left rear wheel speed sensor signal fault). Inspection found the left rear wheel speed sensor harness had chafed through against the chassis, shorting the signal wire to ground. The left rear tone ring also had slight deformation. Resolution: Repaired the damaged harness and added protection. Replaced the left rear wheel bearing assembly (including tone ring). Recalibrated the ABS system. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD F3 right front wheel speed sensor air gap out of specification

✓
Symptoms: ABS warning light illuminates when vehicle speed exceeds 30 km/h; fault occurs more frequently on rough roads. Diagnosis: Retrieved DTC C024501 series. Monitored live data and found intermittent signal dropouts from the right front wheel speed sensor. Inspection revealed heavy metallic debris on the sensor head and loose mounting bolts, causing an air gap exceeding 1.5 mm (specification: 0.3–1.2 mm). Repair: Cleaned the sensor head and tone ring. Repositioned the sensor to achieve the specified air gap. Torqued the mounting bolts to 10 N·m. Cleared the DTCs and verified normal operation during a 60 km/h road test.
BYD DTC AI Analysis

BYD Surui ESP Limited Function Fault

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Symptoms: Dashboard displayed 'ESP function limited', vehicle unstable during cornering, traction control ineffective in rain and snow. Diagnosis: VDS scan retrieved DTC C024501 and related codes. Right rear wheel speed sensor signal voltage measured below 0.5V (abnormal). Traced wiring and found right rear sensor harness chafed through against body sheet metal, signal wire shorted to ground with internal sensor damage. Resolution: Repaired damaged harness and rerouted with corrugated tubing, replaced right rear wheel speed sensor. Dynamic test confirmed ESP function restored.
Original source ↗
BYD DTC AI Analysis

BYD E5: Intermittent wheel speed sensor signal loss

✓
Symptoms: ABS warning light on intermittently, occasionally going out after driving some distance. Normal at low urban speeds; light occasionally comes on at highway speeds. Diagnosis: Scan tool showed history DTC C024501. Live data revealed right front wheel speed signal intermittently dropped to zero. Inspection found sensor connector pins slightly expanded causing poor contact, plus minor harness chafing near the steering knuckle. Solution: Repaired harness chafing, adjusted connector pin tension for reliable contact, and applied waterproof sealant. 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.