AU
B16301B

This fault code indicates the Airbag Control Unit (ACU) detects an open circuit or high resistance in the communication circuit between the front passenger side airbag (usually installed on the outboard side of the front passenger seat or inside the B-pillar trim panel) and the ACU — Seal U

Safety System

This fault code indicates the Airbag Control Unit (ACU) detects an open circuit or high resistance in the communication circuit between the front passenger side airbag (usually installed on the outboard side of the front passenger seat or inside the B-pillar trim panel) and the ACU.

Specifically, the ACU cannot detect the standard 2-3 ohm resistance value in this airbag circuit and determines a 'disconnected' state.

This prevents the side airbag from deploying normally during a side impact, severely reducing side impact protection for the front passenger.

The system simultaneously illuminates the SRS fault warning light on the instrument cluster and may trigger the system safety protection mechanism, disabling the entire airbag system to prevent accidental deployment.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Front passenger side airbag yellow connector (usually located under or on the side of the seat) is loose or disconnected, or the locking mechanism is not fully engaged, causing poor contact or an open circuit.
  • 2Frequent fore/aft seat adjustment or pinching by the seat frame causes internal breakage or insulation damage to the airbag wiring harness at bend points (especially near the seat slide rails).
  • 3Open circuit or abnormal resistance (outside the standard 2-3Ω range) in the airbag module internal gas generator coil, causing the ACU to detect an open circuit.
  • 4Water ingress, damp conditions, or oxidation corrodes connector pins and forms verdigris (green rust), causing excessive contact resistance that the system detects as an open circuit.
  • 5Failure to correctly route the airbag wiring harness after seat repairs (such as replacing the seat cover or repairing the slide rail), causing the connector to pull loose or terminal pins to back out.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000/VDS3.0) to read the fault code. Confirm B16301B is a current fault (Current DTC) rather than a history fault, and record the freeze frame data.
  • 2
    Perform the safety procedure: turn off the ignition switch, disconnect the battery negative terminal, and wait at least 3 minutes to fully discharge the SRS capacitor. Never work on the airbag system with the power supply connected.
  • 3
    Remove the front passenger seat side trim panel and locate the yellow-marked airbag wiring harness connector. Verify the connector is fully seated. Press to confirm the locking tab engages fully (listen for a 'click').
  • 4
    Check the wiring harness near moving parts, such as seat slide rails and frames, for wear or pinch marks. Gently pull the harness to check for internal breaks. Measure harness continuity if necessary (use a high-impedance digital multimeter; never use an analog multimeter to directly measure the airbag assembly).
  • 5
    Check if the connector pins are oxidized, backed out, or deformed. Clean with electrical contact cleaner. Repair or replace the pins if necessary.
  • 6
    If the wiring harness is normal, read the airbag circuit resistance value using the diagnostic tool, or disconnect the airbag connector and test with a dedicated airbag simulator to determine whether the fault is in the wiring harness or the airbag module.
  • 7
    Repair or replace the faulty component based on the inspection results: repair the wiring harness, replace the connector, or replace the front passenger side airbag assembly (record the old and new part numbers when replacing the airbag).
  • 8
    Reconnect the battery, clear the fault code, and perform an SRS system self-check (turn the ignition switch to the ON position; the SRS warning lamp should illuminate and then turn off). Perform a road test to confirm the fault does not recur.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Loose passenger-side airbag connector caused SRS warning light on Yuan PLUS

✓
The dashboard displayed a constant SRS warning light accompanied by a system alert tone. The scan tool retrieved DTC B16301B (front passenger side airbag disconnected). The technician removed the front passenger seat side trim panel and found the yellow side airbag connector not fully locked, with an approximately 2mm gap. The technician suspected this was due to incomplete insertion following a previous seat repair. The technician reconnected the plug firmly and confirmed the locking mechanism engaged. After clearing the fault code, the SRS light went out and the system returned to normal. During diagnosis, the technician measured normal wiring harness continuity and found the airbag module resistance within the standard range.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Repaired open circuit in Yuan PLUS EV side airbag wiring harness caused by chafing

✓
After starting the vehicle, the dash continuously displayed 'Please check airbag system' and DTC B16301B would not clear. The passenger seat side airbag connector showed no visible damage, but measuring the wiring between the ACU and airbag plug revealed an open circuit. Further inspection found the harness rubbing against the seat frame behind the seat rail; long-term seat adjustment had worn through the insulation and caused the break. Re-soldered the broken wiring, reinforced the insulation with heat shrink tubing, rerouted the harness and fitted abrasion-resistant sleeving to ensure safe clearance from moving parts. Performed system configuration and self-test using a scan tool after repair. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Seat refitted without connecting airbag connector on Qin EV

✓
The customer reported the SRS warning light on after cleaning the seats. The scan tool retrieved DTC B16301B, pointing to the passenger's side airbag. Inspection found the passenger seat had been removed and reinstalled; the operator missed the airbag harness connector on the side of the seat during reassembly, leaving the yellow plug completely disconnected. Reconnected the plug, confirmed the lock, and cleared the DTC, which resolved the issue. This case highlights that when removing and installing seats with airbags, technicians must strictly follow the workshop manual and ensure all electrical connections are reconnected.
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]