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 — Atto 3

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 Atto 3 indicates an abnormal or lost signal from the left front wheel speed sensor. Severity is medium, as it can disable ABS, ESC, and automatic emergency braking functions. Common causes include a failed wheel speed sensor or an incorrect sensor-to-tone-ring gap from bearing wear, loose bolts, or bracket damage. The recommended fix is to 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 — Atto 3
  • 1Left front wheel speed sensor failure: Internal coil open circuit (magnetoelectric type resistance should be 1.2-1.6kΩ) or damaged Hall element, causing no signal output or insufficient output amplitude.
  • 2Abnormal sensor installation gap: Bearing wear, loose sensor retaining bolts, or mounting bracket deformation causes the gap between the sensor and tone ring to exceed the standard value (0.3-1.2 mm), attenuating signal amplitude.
  • 3Wiring harness and connector faults: Internal wire breakage (commonly near the wheel arch liner) due to tension on the chassis wiring harness during steering or driving over bumps, connector water ingress and oxidation, or shielding layer damage causing electromagnetic interference.
  • 4Reluctor ring fault: Iron filings or mud adhering to the reluctor ring surface (common after driving through water), 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 faulty A/D conversion module causes the unit to misjudge 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. Inspect the wiring harness routing for signs of abrasion or crushing. Inspect 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 attached foreign matter. Clean metal filings and oil contamination 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 circuit continuity for the power wire (+12V), signal wire, and ground wire; resistance should be <1Ω. Measure harness insulation to ground; resistance should be >10MΩ.
  • 4
    Sensor resistance/voltage test: For a magnetic inductive sensor, resistance should measure 1.2-1.6kΩ (20℃); for a Hall sensor, with the ignition ON, supply voltage should measure 12V±0.5V, and signal wire static voltage should measure 2.0-2.5V.
  • 5
    Dynamic signal test: Connect an oscilloscope or multimeter set to the AC range. 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 tone ring peak. Standard: 0.3-1.2 mm. If out of specification, check the sensor mounting bolt torque (typically 8-10 N·m), or replace the sensor/adjust the shim.
  • 7
    Component replacement verification: If the above checks are normal, replace the left front wheel speed sensor and test drive the vehicle. If the fault disappears, the sensor has failed; 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 Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 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.