AU
B166100

DTC B166100 indicates a communication interruption or data abnormality between the Airbag Control Unit (ACU) and the Front Right Impact Sensor — Seal U

Safety System

DTC B166100 indicates a communication interruption or data abnormality between the Airbag Control Unit (ACU) and the Front Right Impact Sensor.

The sensor mounts on the right front longitudinal beam or the right side of the bumper reinforcement beam to detect front-right collision acceleration.

This communication error prevents the ACU from receiving real-time collision signals from this area, forcing the airbag system into a degraded mode.

During a frontal collision, the system cannot accurately determine impact severity and direction, delaying or preventing deployment of the front right airbag and right-side pretensioner, which severely compromises occupant protection.

This fault constitutes an active safety system failure and requires immediate repair.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Front right crash sensor wiring harness connector loose, oxidized, or corroded by water ingress (sensor located in the front bumper area; vulnerable to wading or impact from high-pressure car wash jets).
  • 2Internal fault in the sensor body accelerometer or communication IC chip (due to prolonged vibration or electromagnetic interference)
  • 3Open or short circuit in the front wiring harness (improperly secured wiring harness after front-end accident repairs, or wire breakage due to long-term vibration)
  • 4SRS control module (ACU) internal CAN/LIN transceiver fault; unable to receive sensor data.
  • 5Abnormal sensor supply voltage (blown fuse or wiring voltage drop causing operating voltage to fall below 9V)
What To Do
  • 1
    Use the BYD VDS diagnostic tool to read all fault codes, check for an accompanying B166000 (parameter error) or other communication faults, and record the freeze frame data.
  • 2
    Switch off the ignition, disconnect the negative battery terminal, and wait 90 seconds. Check the right front crash sensor connector (located at the front of the right front longitudinal beam or on the right side of the bumper reinforcement) for looseness, water ingress, or pin corrosion.
  • 3
    Measure the voltage at the sensor connector power supply terminal (usually pin 2) (normal: 9-12V). Measure the resistance to ground at the ground terminal (pin 1) (should be less than 1Ω). Check the insulation of the signal wire (pin 3) to ground and power.
  • 4
    Disconnect the ACU and sensor. Use a multimeter to measure harness continuity: wiring resistance between the sensor connector and ACU must be less than 2Ω, and wiring resistance to ground/power must be greater than 10MΩ.
  • 5
    Perform a sensor swap test: Swap the right-front and left-front sensors. If the fault code follows the sensor, replace the sensor. If the fault remains, check the ACU or wiring harness.
  • 6
    After repair, reconnect the battery. Use VDS to perform 'SRS System Self-diagnosis' and 'Crash Sensor Calibration' (if applicable). Clear the fault codes and perform a road test to verify.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Right front crash sensor communication lost after wading

✓
A 2019 Qin Pro DM had a steady airbag warning light after wading through floodwater in heavy rain. Read DTC B166100. Found obvious water staining inside the right front collision sensor connector under the longitudinal beam—terminals oxidized black. Cause: aged waterproof seal let water in during wading, shorting the signal wire to ground. Repair: cleaned terminals, replaced seal, applied contact protectant, reset. Fault cleared.
BYD DTC AI AnalysisFrom Chinese market (translated)

Wiring harness not secured after accident repair caused intermittent fault

✓
After front collision repairs on a 2018 Qin PRO petrol variant, the instrument cluster intermittently displayed an airbag fault, DTC B166100 (intermittent). Inspection found that the front bumper harness—replaced during the accident repair—was missing its retaining clips at the right front side member. The harness rubbed against a sharp metal body edge, damaging the insulation and causing the copper wires to short intermittently to earth. Repaired the damaged harness, wrapped it in special fabric tape, re-secured the harness routing, and maintained at least 20 mm clearance from sharp edges.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal sensor fault caused communication failure

✓
A 2019 Qin PRO DM's airbag warning light suddenly illuminated while driving with no collision. VDS detected DTC B166100 (current fault). Wiring harness voltage (12V), ground, and circuit continuity all tested normal. Sensor signal output showed no waveform (normal should be CAN/LIN or PWM signal). Determined the sensor's internal communication chip had failed. Replaced the right front impact sensor (part number: BYD-3636400-XX), performed system configuration write, and resolved the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Loose connector caused intermittent warning while driving.

✓
Customer reported the airbag warning light on their 2018 Qin Pro would flash occasionally when driving over speed bumps or rough roads. Diagnosis revealed stored DTC B166100. Inspection found the right front impact sensor connector locking tab broken, which prevented the connector from locking fully and caused momentary disconnection under vibration. Cause: damage to the locking mechanism from forceful plugging/unplugging during previous unprofessional repair work. Repair: replaced the wiring harness connector terminal (or entire harness plug) and ensured the clip locked securely. Road tested 30 km with no fault recurrence.
BYD DTC AI AnalysisFrom Chinese market (translated)

False positive for SRS control module internal fault

✓
A Qin PRO DM simultaneously stored B166100 (right front) and B165100 (left front) communication errors. Checked power supply and wiring to both sensors – all normal. Sensors tested individually also normal. Suspected ACU internal communication bus fault. Inspected ACU connector and found slight oxidation on multiple pins (likely from internal moisture). Repair: Cleaned ACU connector pins, treated with WD-40 Precision Electrical Cleaner, applied protective grease and reconnected. If fault persists, replace ACU and program.
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. Sources: [1]