AU
C003108

This DTC indicates the ABS control unit detects an abnormal or completely lost signal input while monitoring the left front wheel speed sensor — Seal 6 EV

Braking System

This DTC indicates the ABS control unit detects an abnormal or completely lost signal input while monitoring the left front wheel speed sensor.

The wheel speed sensor (typically magnetic or Hall-effect) generates a pulse signal by monitoring the rotation of the tone ring on the half shaft or wheel hub.

Systems such as ABS, ESC, and EPB rely on this signal to calculate wheel speed.

The control unit sets C003108 when the signal voltage falls outside the threshold (<0.5V or >4.5V), the signal frequency is abnormal, or intermittent interruptions occur.

This fault prevents accurate detection of the left front wheel speed.

It triggers ABS failure, deactivates the ESC system, disables the automatic emergency braking system, and potentially affects the coordinated control of the energy recovery system.

On pure electric models such as the E5, it also affects motor torque distribution and coasting energy recovery smoothness.

The C003108 fault code on the Seal 6 EV indicates an abnormal or lost signal from the left front wheel speed sensor. Severity is medium because ABS, ESC, AEB, and energy recovery control may be affected. Common causes include a failed wheel speed sensor or an incorrect sensor-to-tone-ring gap from bearing wear, loose bolts, or bracket damage. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Left front wheel speed sensor failure: Internal coil open circuit (magnetic type resistance: 1.2-1.6kΩ) or damaged Hall element, resulting in no signal output or insufficient output amplitude.
  • 2Abnormal sensor installation gap: Bearing wear, loose sensor retaining bolts, or a deformed mounting bracket causes the gap between the sensor and the tone ring to exceed the standard value (0.3-1.2mm), reducing signal amplitude.
  • 3Wiring harness and connector faults: Chassis wiring harness stretches during steering or driving over bumps, causing internal wire breakage (commonly near the fender liner); water ingress and oxidation in the connector; or damaged shielding layer allowing electromagnetic interference.
  • 4Reluctor ring fault: Iron filings or mud adhering to the reluctor ring surface (common after wading), reluctor ring deformation (tire lever damage during tire repair), missing teeth, or tooth surface corrosion, causing signal waveform distortion.
  • 5ABS control unit internal fault: Damaged input-stage amplifier circuit or A/D conversion module fault causes the unit to misinterpret normal signals as abnormal (confirm via process of elimination).
What To Do
  • 1
    Initial inspection: Raise the vehicle. Visually inspect the left front wheel speed sensor for damage. Check the wiring harness routing for chafing or crush marks, and check the connector for looseness, water ingress, or oxidation.
  • 2
    Reluctor ring inspection: Rotate the left front wheel and inspect the reluctor ring for missing teeth, deformation, cracks, or foreign matter. Clean metal filings and oil from the reluctor ring surface. Check the driveshaft bearing for excessive clearance (replace if radial play >0.5 mm).
  • 3
    Circuit continuity test: Disconnect the ABS pump connector and sensor connector. Measure the circuit continuity of the power wire (+12V), signal wire, and ground wire; resistance must be <1Ω. Measure the wire harness insulation to ground; resistance must be >10MΩ.
  • 4
    Sensor resistance/voltage test: For a magnetic inductive sensor, resistance must measure 1.2-1.6kΩ (20℃); for a Hall sensor, with the ignition ON, supply voltage must measure 12V±0.5V, and signal wire static voltage must measure 2.0-2.5V.
  • 5
    Dynamic signal test: Connect an oscilloscope or a multimeter set to AC voltage and rotate the wheel. The magnetic induction type must output >100mV AC voltage that increases with wheel speed. The Hall type must output a 0-5V square wave signal.
  • 6
    Gap measurement and adjustment: Use a feeler gauge to measure the gap between the sensor and the peak of the tone ring. Standard: 0.3-1.2 mm. If out of specification, check the sensor retaining bolt torque (usually 8-10 N·m), replace the sensor, or adjust the shim.
  • 7
    Component replacement verification: If the above checks are normal, replace the left front wheel speed sensor with a known good unit and test drive the vehicle. If the fault clears, the sensor is defective. If the fault persists, check the ABS pump.
Real-World Cases
BYD DTC AI Analysis

E5 sensor body aging caused intermittent signal loss

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Vehicle: 2019 BYD E5, 80,000 km. Symptoms: ABS light intermittent, especially on rough roads. Diagnostic tool read C003108 (current fault). Diagnosis: Sensor resistance measured 1.3 kΩ at rest but jumped to open circuit when tapping the body. Found dry solder joint on internal coil. Fix: Replaced left front wheel speed sensor (SK-3630100). Cleared codes and road-tested 20 km. ABS function normal.
BYD DTC AI Analysis

Qin Pro wiring harness connectors oxidized and corroded after water ingress

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Vehicle: BYD Qin Pro DM. Fault: Warning light constantly on. Symptoms: ABS and ESC lights illuminated simultaneously after wading through heavy rain. C003108. Diagnosis: Sensor power supply normal. Signal line voltage only 0.3V (abnormal). Removed left front fender inner harness connector; found mud and water residue inside with pins oxidized green. Repair: Cleaned connector with electronic cleaner, applied conductive paste, dried and reinstalled. Wrapped harness connector with waterproof tape and adjusted mounting position to prevent water ingress. Fault cleared.
BYD DTC AI Analysis

Excessive bearing clearance on Song Plus caused abnormal signal

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Vehicle: BYD Song Plus EV, 60,000 km. Symptoms: ESC warning light flashing above 80 km/h. Scanned DTC C003108 (historic). Diagnosis: Raised the vehicle. Rocked the left front wheel and found noticeable radial play in the wheel bearing (approx. 2 mm). Rotated the wheel and observed excessive variation in the gap between the sensor and tone ring. Signal was normal at low speed, but tone ring wobble caused signal loss at high speed. Resolution: Replaced the left front wheel hub bearing assembly (including tone ring). Reinstalled the sensor and adjusted the gap to 0.8 mm. No recurrence.
BYD DTC AI Analysis

Iron filings on E5 tone ring caused signal waveform distortion

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Vehicle: 2018 BYD E5, commercial vehicle. Symptoms: ABS warning light on, DTC C003108. ABS triggers early during braking (false activation). Diagnosis: Sensor and wiring tested normal. Disassembly revealed the reluctor ring coated with heavy brake dust and metallic debris, causing abnormal magnetic flux changes and noisy signal output. Fix: Thoroughly cleaned the reluctor ring surface and blew out the sensor head with compressed air. Inspected brake pads—severely worn, generating excessive dust. Replaced the brake pads. Fault resolved.
BYD DTC AI Analysis

Song Pro wiring harness wear causes intermittent open circuit

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Vehicle: BYD Song Pro, 40,000 km. Symptom: ABS warning light illuminates at full steering lock and extinguishes when straightened. Diagnosis: Repeatedly simulated full left lock. When the fault occurred, the sensor signal line showed infinite resistance to ground. Inspected the harness along the left front shock tower; the harness had stretched at full lock, with internal conductors partially fractured and only a few strands remaining. Resolution: Cut out the damaged section, repaired with soldered same-specification wire, rerouted clear of the steering sweep, and secured to the body bracket. Fault resolved.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV overview →
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.