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B163C

Fault code B163C has different definitions across BYD vehicle platforms — Atto 3

Safety System

Fault code B163C has different definitions across BYD vehicle platforms.

On early e-Platform 2.0 models (e.g., Yuan 2019, Song MAX 2019, Qin 2020), this fault code indicates excessive resistance in the front passenger side airbag.

The SRS system detects that the right-hand Seat Side Airbag ignition circuit resistance exceeds the calibrated threshold (normal range: 2.0–3.0 Ω; fault threshold: >4.5 Ω).

This condition can prevent proper airbag deployment during a collision.

On newer e-Platform 3.0 and DM-i models (e.g., Han EV, Tang DM-i, Seal, Qin Plus), the ADAS system defines B163C as a Front Millimeter Wave Radar sensor signal fault or communication interruption.

This fault indicates abnormal communication between the radar and the ADAS controller (ACC/ESP module) exceeding the specified time (usually >100 ms), or a radar self-check detecting an internal hardware fault (e.g., RF front-end anomaly or signal processing unit fault).

This disables functions including Adaptive Cruise Control (ACC), Automatic Emergency Braking (AEB), and Intelligent Cruise Control (ICC).

Poor wiring harness connections, airbag unit aging, or connector oxidation typically cause excessive resistance in the airbag system.

Physical damage, water ingress, or incorrect installation angles typically cause radar system faults.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Front millimeter-wave radar sensor assembly damaged: Front bumper impacts, high-speed stone strikes, water ingress from high-pressure car washing, or long-term vibration causing internal circuit board corrosion or RF module failure.
  • 2Radar mounting position misaligned: Failing to tighten the radar to the standard torque (usually 8-10 Nm) during reinstallation after front bumper repair (painting or sheet metal work) causes the horizontal or pitch angle to deviate beyond the allowable ±3° range.
  • 3Wiring harness and connector faults: backed-out radar connector pins, oxidized pins, failed seal causing water ingress (common after car washes or heavy rain), poor connection or abnormal resistance in the CAN-H/CAN-L lines.
  • 4Radar surface contamination or obstruction: Ice, snow, mud, metallic stickers, or paint covering the radar surface causes abnormal signal transmission/reception, leading the system to incorrectly identify a hardware fault.
  • 5Power supply system fault: Unstable radar supply voltage (below 11V or above 16V), loose ground point, or voltage drop in the ACC/IGN power supply circuit.
What To Do
  • 1
    Initial inspection: Visually inspect the front bumper area for impact damage, radar mounting bracket deformation, and scratches or contaminants on the radar surface. Check the vehicle history for recent front-end repairs or high-pressure washing.
  • 2
    Diagnostic scan: Use the BYD dedicated diagnostic tool (VDS2000/3000) to read the fault code status and confirm if B163C is a current fault (Current). Check the freeze frame data (Freeze Frame) for the vehicle speed and ambient conditions recorded when the fault occurred. Enter the ADAS system to read the data stream. Check the radar communication status, supply voltage, and horizontal/vertical angle data.
  • 3
    Electrical measurement: Disconnect the radar wiring harness connector and measure the power supply terminal voltage (12V ± 0.5V, key ON) and ground resistance (<1Ω). Measure the CAN bus voltage (CAN-H 2.5-2.7V, CAN-L 2.3-2.5V) and terminating resistance (approx. 60Ω, measure with power off).
  • 4
    Physical inspection and cleaning: Check inside the connector for water stains, corrosion, or backed-out pins. Clean the connector and apply conductive grease if necessary. Check the radar mounting surface for flatness and the bracket for deformation.
  • 5
    Component replacement verification: Swap the radar with a known-good unit from the same vehicle model. If the fault transfers, the radar unit is faulty. Note: On some models, the radar is bound to the VIN. A direct swap may trigger an anti-theft fault. Use a diagnostic tool to match the radar.
  • 6
    Replacement and Calibration: After installing a new radar, calibrate it on a level surface using dedicated ADAS calibration equipment (calibration frame, reflector board, or optical calibrator). Calibration includes adjusting the horizontal (yaw), pitch, and roll angles. The error must be <0.5°.
  • 7
    Function verification: Clear the fault code and perform a road test (vehicle speed must be >30km/h). Confirm the ACC follow function, AEB warning function, and lane keeping system operate normally, and no fault lights illuminate on the instrument cluster.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro DM front millimetre-wave radar fault after collision

✓
Symptoms: After starting, the dashboard displayed "Please check adaptive cruise control system" and the ACC function failed. Stored DTCs B163C (front millimeter-wave radar signal fault) and U015587 (lost communication with front millimeter-wave radar). Diagnosis: Inspection found slight displacement of the front radar mounting position (the vehicle had a recent minor collision). Live data showed communication abnormalities. Power supply measured 12.4V (normal); CAN bus voltage was normal. Reinstalling and calibrating the radar did not fix the fault. Disassembly revealed slight scratches on the sensor surface. We determined the collision damaged the internal RF module. Repair: Replaced the front millimeter-wave radar sensor. Calibrated horizontal and vertical angles using a dedicated diagnostic tool. Cleared fault codes and test-drove the vehicle. ACC function returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Front radar water ingress caused intermittent fault on BYD Han EV

✓
Symptoms: While driving, the warning 'Intelligent Pilot System Limited' appeared suddenly. Cruise control could not be activated. DTC B163C present (current status, will not clear). Diagnosis: Inspected the front end—no collision damage evident. However, freeze frame data indicated the fault occurred during light rain. Inspected the radar connector and found internal water ingress (owner had recently used a high-pressure car wash). Cleaned the connector and the fault temporarily disappeared, but returned after driving. Measured the communication lines and found resistance fluctuating abnormally. Determined the radar unit had developed an intermittent internal short due to water ingress. Repair: Replaced the front millimetre-wave radar assembly. Applied waterproof sealant to the connector and rerouted the wiring loom protective boot. Performed ADAS system calibration. Fault completely resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM-i radar calibration fault after bumper respray

✓
After a dealership front bumper respray, the adaptive cruise control (ACC) failed and the cluster displayed "Check ADAS System". Scanned DTCs B163C (front millimeter-wave radar sensor fault) and B164C (front millimeter-wave radar not calibrated). Inspection found the radar mounting angle had shifted approximately 5° during reassembly. Attempted to clear the codes; cleared B164C, but could not clear B163C. Measured power supply and CAN communication, both normal. Determined the radar sustained physical impact during removal/installation, damaging the internal gyroscope or RF components. Replaced the front millimeter-wave radar. Calibrated the radar horizontal and pitch angles using ADAS calibration equipment per the workshop manual. Road test confirmed ACC, AEB, and other functions operated normally.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Plus EV radar water ingress due to seal failure

✓
Symptoms: During normal driving, the instrument cluster suddenly displayed 'Front Assist System Fault'. ACC and AEB functions were inoperative. Scan tool read code B163C (front millimetre-wave radar internal fault). Diagnosis: Bumper showed no collision damage; radar appeared intact externally. Freeze frame data showed vehicle speed 80 km/h and light rain when the fault occurred. Swapped the radar with a unit from a working same-model vehicle; the fault followed the radar, confirming a fault inside the radar unit. Disassembled the radar and found moisture corrosion on the internal PCB. Inspected the front bumper liner and found a damaged seal allowing water ingress. Solution: Replaced the front millimetre-wave radar, repaired the bumper liner seal, and performed radar calibration. Fault eliminated.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Seal: Poor radar plug connection on new vehicle

✓
Symptoms: One week after delivery, the instrument cluster intermittently displayed 'Intelligent Driving System Fault' while driving. The warning cleared after restarting but later became permanent. ACC and lane keeping assist were unavailable. Read DTC B163C (front millimetre-wave radar communication fault). Diagnosis: Checked the radar installation – no abnormalities. Measured harness supply voltage, earth, and CAN line voltage – all normal. Inspected the radar connector and found the terminals slightly backed out. Reconnected the plug and the fault cleared, but it returned on rough roads. Determined poor contact was caused by the connector not fully seated during production assembly. Solution: Replaced the front millimetre-wave radar harness connector repair kit. Ensured the terminals were fully seated and fitted a securing clip. Performed radar calibration and system configuration. Road tested and verified all functions normal.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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. Sources: [1]