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B163C

Fault code B163C has different definitions across BYD vehicle platforms — Seal U

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.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

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

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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.
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BYD DTC AI Analysis

Front radar water ingress caused intermittent fault on BYD Han EV

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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.
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BYD DTC AI Analysis

BYD Tang DM-i radar calibration fault after bumper respray

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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.
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BYD DTC AI Analysis

BYD Qin Plus EV radar water ingress due to seal failure

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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.
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BYD DTC AI Analysis

BYD Seal: Poor radar plug connection on new vehicle

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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.
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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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.