AU
C003204

DTC C003204 indicates an electrical fault in the left front wheel speed sensor (WSS) circuit within the BYD ABS system — Seal U

Braking System

DTC C003204 indicates an electrical fault in the left front wheel speed sensor (WSS) circuit within the BYD ABS system.

This variable reluctance or Hall-effect sensor supplies the wheel speed signal to the ABS/ESC control unit.

The control unit sets this code upon detecting an open circuit, short to ground, short to power, or abnormal signal interruption in the sensor circuit.

In BYD new energy vehicles, this fault impairs normal ABS/ESP operation.

It also limits regenerative braking, disables cruise control, disrupts four-wheel-drive torque distribution (if applicable), and may trigger a "Check braking system" warning.

Because electric vehicles rely on wheel speed signals to calculate coasting energy recovery and estimate driving range, this fault reduces driving smoothness and causes inaccurate range displays.

In severe cases, it triggers false ABS activation or complete ABS failure, compromising driving safety.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Left front wheel inner wiring harness wear: Long-term bending at the steering knuckle or suspension movement points damages the harness insulation, causing an intermittent open circuit or short to ground.
  • 2Sensor connector oxidation/looseness: Wading or damp environments cause oxidation and corrosion of the connector pins, or a damaged locking tab causes excessive contact resistance.
  • 3Sensor failure: Internal coil open circuit, magnetic core demagnetization, or Hall element aging causing abnormal or no signal output.
  • 4Tone ring (magnetic encoder) fault: Driveshaft or wheel hub bearing tone ring deformed, missing teeth, contaminated with iron filings or dirt, or installation gap out of tolerance (standard 0.3-1.2 mm).
  • 5ABS pump ECU connector fault: Backed out or corroded terminal pins at the control unit, or damaged internal sampling circuit (low probability, but inspect).
What To Do
  • 1
    Visual inspection: Check the left front wheel speed sensor connector for looseness, oxidation, or water ingress. Check the wiring harness at the steering knuckle and control arm for wear, damaged insulation, or pinch marks.
  • 2
    Diagnostic tool check: Use VDS or a generic diagnostic tool to read the fault code status (current/history). Check the data stream for an abnormal left front wheel speed (displays 0, fluctuates, reads 255 km/h, or differs excessively from the other three wheels).
  • 3
    Resistance measurement: Disconnect the sensor connector and measure the resistance across the sensor terminals. The normal range for magnetic inductive types is 1.0-1.6 kΩ. For Hall effect types, refer to the manual. Replace the sensor if the resistance is out of specification.
  • 4
    Power supply check: Turn ignition ON. Measure voltage at the power supply terminal of the harness-side connector. Voltage should be 12V±0.5V. If abnormal, check the fuse and power supply circuit.
  • 5
    Signal test: Use an oscilloscope or multimeter set to DC voltage. Rotate the wheel and measure the signal wire voltage. The voltage must pulse between 0-5V. If there is no change or the voltage remains fixed, the sensor or tone ring is faulty.
  • 6
    Circuit continuity test: Disconnect the ABS pump ECU connector and sensor connector. Measure the continuity of the signal wire, ground wire, and power wire (should be <1Ω) to check for an open circuit.
  • 7
    Insulation test: Measure the insulation resistance of the signal wire to ground and to the power supply. Resistance must be >10MΩ to prevent intermittent short circuits from causing abnormal signals.
  • 8
    Tone ring inspection: Inspect the magnetic tone ring on the half shaft or wheel hub bearing for deformation, missing teeth, or dirt. Use a feeler gauge to verify the gap between the sensor and the tone ring is 0.3-1.2 mm.
  • 9
    Road test verification: After repair, clear the fault code. Monitor the data stream for four-wheel synchronization while driving. Perform an emergency braking test to confirm normal ABS/ESP function.
Real-World Cases
BYD DTC AI Analysis

BYD Song Pro left front wheel speed sensor signal fault

✓
Symptoms: ABS and ESP warning lights lit together. "Clunking" noise during low-speed cornering; speedometer showed intermittent fluctuation. Diagnosis: Launch X431 scan pulled DTC C003204. Sensor resistance measured 1.2 kΩ (normal). Signal voltage jumped around when rotating the wheel, indicating intermittent open circuit. Found oxidation inside the connector. Fix: Cleaned sensor connector contacts and applied conductive grease. Fault persisted, so replaced left front wheel speed sensor assembly. Cleared codes and road-tested 10 km; live data showed normal wheel speed signals.
Original source ↗
BYD DTC AI Analysis

BYD Qin DM left front wheel speed sensor circuit fault

✓
Symptoms: ABS warning light stayed on after startup. ABS engaged prematurely during braking with pedal kickback. Hybrid system displayed "Check ESP System". Regenerative braking limited. Diagnosis: VDS scan tool read DTC C003204. Live data showed left front wheel speed at 0 km/h while the vehicle was moving. Inspection found the left front inner wiring harness chafed against the steering knuckle; damaged insulation caused an intermittent short to ground. Continuity testing confirmed an intermittent open in the white signal wire. Resolution: Repaired the damaged harness with heat-shrink tubing. Re-routed and secured the harness to prevent contact with the steering knuckle. Cleared fault codes and performed the ABS pump bleed. Road test confirmed the fix.
Original source ↗
BYD DTC AI Analysis

BYD Tang Petrol: Left front wheel speed sensor performance fault

✓
Symptoms: ESP warning light flickers intermittently above 80km/h; 4WD mode automatically disengages with "4WD system fault" warning; braking distance noticeably increased. Diagnosis: Dedicated diagnostic tool retrieved DTC C003204 (Performance/Range fault). Live data showed a consistent 5-8km/h deviation between left front wheel speed and the other three wheels. Sensor installation gap measured 1.8mm (exceeds 0.3-1.2mm specification). Cleaned iron debris from sensor head; deviation persisted. Fix: Replaced OEM left front wheel speed sensor. Adjusted sensor-to-tone ring gap to 0.8mm using feeler gauges. Road test confirmed all four wheel speed signals synchronised in live data; ESP and 4WD functions returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD F3: Intermittent signal loss from left front wheel speed sensor

✓
Symptoms: ABS warning light intermittent with no pattern, triggers easily on rough roads and may clear on smooth surfaces. No drivability issues. Diagnosis: Generic scan tool retrieved DTC C003204 (history). During dynamic testing, manually rotating the left front wheel caused the data stream to intermittently spike to 255 km/h then drop to zero. Found the sensor connector lock tab damaged and connection loose. Sensor supply voltage measured 8-12V fluctuation (spec: stable 12V). Solution: Replaced the sensor plug (with wiring harness connector). Checked ABS pump ECU supply circuit and found oxidation at the battery negative ground point. Cleaned and tightened the ground cable. Fault cleared. Monitored one week with no recurrence.
Original source ↗
BYD DTC AI Analysis

BYD e5 Pure Electric — Left front wheel speed sensor signal unreliable

✓
Symptoms: Dashboard displayed "Check Brake System." Regenerative braking weakened significantly, cruise control failed to activate, and coasting distance increased with a sensation of neutral coasting. Diagnosis: BYD dedicated diagnostic tool retrieved DTC C003204 (implausible signal). Live data showed spike interference and irregular waveform on the left front wheel speed signal. Inspection found no physical damage to the sensor or harness, but the left front wheel bearing tone ring showed minor distortion with partially missing teeth. Resolution: Replaced the left front wheel bearing assembly (including magnetic tone ring) and preventively replaced the left front wheel speed sensor. Calibrated the ESP system and performed sensor matching. Road test confirmed regenerative braking and cruise control returned to normal.
Original source ↗
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.