AU
B16EF-00

DTC B16EF-00 indicates the SRS (Supplemental Restraint System) detects an open circuit or high resistance condition (typically exceeding 10kΩ) in the Right Rear Impact Sensor or Driver Seat Belt Pretensioner circuit — Seal U

Safety System

DTC B16EF-00 indicates the SRS (Supplemental Restraint System) detects an open circuit or high resistance condition (typically exceeding 10kΩ) in the Right Rear Impact Sensor or Driver Seat Belt Pretensioner circuit.

The system triggers this Hard DTC when it detects interrupted communication between the component and the airbag ECU, or abnormal resistance in the ignition circuit.

In BYD Qin series models, this code typically indicates a LIN bus communication failure or hard-wired connection fault at the side impact acceleration sensor located in the right rear C-pillar or B-pillar.

In Song Pro, Tang DM, Han EV, and other models, this code designates an open circuit in the driver-side seat belt pretensioner ignition circuit.

Upon triggering, the SRS ECU illuminates the airbag warning light, disables the corresponding airbag deployment and pretensioner functions, and enters fail-safe mode.

In extreme cases, this failure may result in a loss of occupant protection during a side impact.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Loose connector, backed-out pins, or corrosion at the right rear impact sensor (located behind the right rear wheel arch liner or inside the C-pillar trim panel, resulting from wading or damp conditions)
  • 2Repeated bending of the driver's seat belt pretensioner wiring harness at the seat slide rail causes fatigue fracture of the internal copper wire, resulting in an intermittent open circuit.
  • 3Damaged crash sensor internal accelerometer element, waterproofing failure, or pretensioner deployed in an accident (internal open circuit in the single-use pyrotechnic device).
  • 4SRS wiring harness chafes against body metal edges, seat rails, or hinges, damaging the insulation and causing an open circuit or short to ground.
  • 5Internal SRS ECU fault (e.g., damaged ignition driver chip) or failure to perform system configuration coding after replacing the pretensioner, resulting in communication failure.
What To Do
  • 1
    Use a dedicated diagnostic tool (Launch X-431 or BYD ED400) to read the complete fault codes and freeze frame data. Confirm whether the fault status is Current or History, and record the vehicle status at the time of occurrence.
  • 2
    Disconnect the battery negative terminal and wait 3 minutes (capacitor discharge). Locate the target component based on vehicle configuration: for Qin series, check the right rear crash sensor (position B16, usually inside the right rear quarter panel); for other models, check the pretensioner connector under the driver's seat.
  • 3
    Visually inspect the connector for looseness, oxidation, water ingress, or damaged locking tabs. Clean the terminals with anhydrous alcohol. Measure component resistance: the pretensioner should be 1.5-2.5Ω (typical value 2.0Ω) and the crash sensor should be 2.0-3.0kΩ. Replace the component if the resistance is out of range.
  • 4
    Perform wiring harness continuity test: Measure continuity from the SRS ECU to the component end; resistance must be <1Ω. Check for short to ground (resistance must be >1MΩ) and short to power (voltage must be 0V).
  • 5
    Inspect wiring harness dynamic interference points: test the seat slide rail through its full travel, and check the wiring harness inside the B-pillar trim and at the door hinge area for pinching, wear, or sharp edge cuts.
  • 6
    Repair the wiring harness: If an open circuit exists, cut out the damaged section and solder an extension using high-temperature wire of the same specification (temperature resistance ≥150°C). Never use ordinary twisted joints. Apply heat-shrink tubing and insulating tape for double protection, and reroute the harness away from moving parts.
  • 7
    Replace the faulty sensor or pretensioner assembly (if the pretensioner deployed, replace the complete assembly; do not repair), and install the improved waterproof connector (if applicable).
  • 8
    Reconnect the battery, clear the fault code, and perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times or via diagnostic tool command). Confirm the airbag warning lamp turns off. Perform a collision simulation test or move the seat to its limit positions to verify the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

Song Pro driver's seat pretensioner wiring harness chafed, open circuit

✓
2019 BYD Song Pro, 42,000 km. Airbag warning light stays on constantly, no other symptoms. Scanned with a Launch X-431 and retrieved DTC B16EF-00: "Driver seat belt pretensioner circuit open", with an occasional historical code B16EF-01. Diagnosis: Inspected the pretensioner connector beneath the driver's seat. Found the connector lock damaged, causing poor contact. Measured infinite resistance (open circuit) across the pretensioner, but resistance returned to 2.0 Ω after gently wiggling the harness. Further inspection revealed the harness had chafed at the seat rail, with internal copper wires fractured and only a few strands still connected. Seat movement caused an intermittent open circuit. Repair: Cut out the damaged harness section and soldered in an extension using same-spec high-temperature wire (twist joints not acceptable). Rerouted the harness clear of the seat rail travel area. Replaced the pretensioner connector. Cleared fault codes, then moved the seat through its full range multiple times—no recurrence.
Original source ↗
BYD DTC AI Analysis

Qin Plus DM-i seat rail pinched wiring harness short circuit

✓
Symptoms: 2021 BYD Qin Plus DM-i, 8 months old. After adjusting the seat to the full forward position, the owner noticed the airbag warning light on the dash suddenly flashing. Scan tool read DTC B16EF-00. All other vehicle functions normal. The warning light sometimes turned off automatically when the seat was moved rearward. Diagnosis: Moving the seat to the full forward position triggered DTC B16EF-00; moving it back made the DTC disappear. Removing the seat revealed the pre-tensioner wiring harness routed incorrectly and pinched by the seat rails. The damaged insulation caused an intermittent short to ground on the signal wire. The pre-tensioner body resistance measured normal at 1.8 Ω, but the harness-to-ground resistance varied during seat movement. Solution: Repaired the damaged harness using insulation tape and heat-shrink tubing for double protection. Rerouted the wiring harness and secured it to the seat frame with cable ties to prevent interference with moving parts. Added a wiring protection sleeve at the seat rails. Cleared the DTC; fault eliminated.
Original source ↗
BYD DTC AI Analysis

Tang DM pretensioner triggered after accident, not replaced

✓
Symptoms: 2018 BYD Tang DM. Low-speed frontal collision at approximately 25 km/h (airbags did not deploy). After the dealership repaired the front bumper, the airbag warning light stayed on continuously. Diagnostics showed active fault code B16EF-00 that could not be cleared. Diagnostic process: The accident repair replaced only the front bumper and crash beam and did not involve the seatbelt system. Inspection found the driver seatbelt pretensioner had triggered during the collision (internal pyrotechnic device detonated), showing infinite resistance. Visual inspection showed slight gap enlargement on the seatbelt retractor housing and colour change at the label (post-trigger indicator). Solution: Replaced the driver-side seatbelt assembly (with pretensioner, part number: BYD-5811100-D). Used a dedicated diagnostic tool to configure and code the airbag system. Performed a system self-test; after passing, cleared the fault code. The airbag warning light went out. The pretensioner is a single-use component and must be replaced after triggering.
Original source ↗
BYD DTC AI Analysis

Han EV pretensioner connector water ingress and corrosion

✓
Symptoms: 2020 BYD Han EV. Intermittent fault—airbag warning light illuminates after rain or washing, sometimes self-extinguishing when dry. DTCs B16EF-00 (current) and B16EF-11 (historic). Normal driving unaffected, but the vehicle fails annual roadworthiness inspection. Diagnosis: Focused inspection on pretensioner connector waterproofing. Found seal ring aged and deformed, allowing water ingress that oxidised the pins and created contact resistance (measured 5.8Ω; normal spec <3Ω). Cleaned with anhydrous alcohol and blow-dried; resistance returned to normal. However, the seal could not be restored, causing repeated water ingress during rain. Repair: Replaced pretensioner connector with improved version featuring double-layer seal (per dealer technical bulletin). Applied special conductive anti-corrosion paste to the pins. Repaired damaged section of wiring harness corrugated tube and wrapped with waterproof tape. Achieved IP65 waterproof rating. Fault permanently resolved.
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.