AU
B16F912

This is an SRS (Supplemental Restraint System / airbag system) DTC — Seal U

Safety System

This is an SRS (Supplemental Restraint System / airbag system) DTC.

It indicates a short to the vehicle power supply (12V/B+) in a safety-related sensor circuit—typically the second signal/communication line of the seat occupancy sensor, seat belt pretensioner sensor, or side impact sensor.

In the BYD DTC structure, "B16F9" designates the second-row Occupant Classification System (OCS) or the seat belt anchorage sensor, and the "12" suffix indicates a short to power.

This fault causes the Airbag Control Unit (ACU) to detect an abnormally high signal voltage.

The ACU then triggers the safety protection mechanism and places the affected airbag circuit into fail-safe mode.

In extreme cases, this prevents correct airbag deployment during a collision or generates false warnings.

Consequently, the system illuminates the airbag warning lamp and prevents vehicle operation.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged wiring harness insulation causes a short to body power circuits (such as the seat heating power wire or constant power circuit). This typically occurs in areas of frequent seat track adjustment or from harness wear inside the sill trim panel.
  • 2Breakdown of sensor internal electronic components or a capacitor short circuit causes the signal line to short directly to the sensor internal power supply terminal.
  • 3Connector terminal corrosion due to water ingress, or misaligned pins (e.g., a bent pin contacting an adjacent power terminal), especially in damp environments under the seat or in vehicles exposed to wading or liquid spills.
  • 4Improper aftermarket modifications (such as installing seat heaters, massage cushions, or tapping power for a dash cam) pierced or damaged the SRS sensor wiring harness insulation.
  • 5Airbag Control Unit (ACU) internal signal processing circuit fault causes the reference voltage output to the sensor to rise abnormally and register as a short to power.
What To Do
  • 1
    Use BYD dedicated diagnostic tool VDS2000/VDS3000 to read the complete fault codes and freeze frame data. Record the vehicle status when the fault occurred. Perform a system self-check to confirm B16F912 is currently present and is a hard fault.
  • 2
    Refer to the vehicle repair manual wiring diagram to locate the specific sensor (usually the second-row seat occupancy sensor or seat belt buckle sensor). Visually inspect the connector for looseness, water ingress, or obvious burn marks.
  • 3
    Disconnect the sensor connector. Use a multimeter to measure the voltage between the 'second wire' on the wiring harness side (usually the signal or LIN wire) and body ground. Normal voltage is close to 0 V or the 5 V reference voltage. A reading of 12 V (battery voltage) confirms a short to power.
  • 4
    Use a sectional troubleshooting method: follow the routing to check the harness securing points at the seat slide rail, under the carpet, and inside the B-pillar trim. Focus on finding chafing points between the harness and sharp metal edges, the seat heater harness, or the power harness. Repair the insulation at any damaged areas, reroute the harness, and install corrugated conduit for protection.
  • 5
    If the wiring harness is intact, measure the resistance between the sensor terminals. If the resistance between the signal wire and the power terminal is 0 or very low, this indicates an internal sensor short circuit. Replace the corresponding sensor (such as the seat occupancy pressure sensor or seat belt buckle switch).
  • 6
    After completing the inspection and repair, reconnect all connectors and use the diagnostic tool to clear the fault codes. Perform SRS system configuration calibration (such as the seat OCS calibration procedure). Finally, perform static and road tests to confirm the warning light turns off and the system generates no new fault codes.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM seat occupancy sensor wiring harness chafed and shorted to the heating wire

✓
The instrument cluster displayed a permanent airbag warning light. VDS read fault code B16F912. Inspection found the wiring harness retaining clip under the second-row seat had detached. The Occupant Classification Sensor (OCS) signal wire insulation had chafed through and contacted the parallel seat heater power wire (12V constant), causing a short to power. Repaired the damaged harness section, rerouted the wiring to avoid the seat rail travel area, and replaced the cable ties. Fault cleared.
BYD DTC AI Analysis

BYD Qin Pro (petrol): Water ingress short-circuited seatbelt pretensioner connector.

✓
The airbag warning light illuminated after the vehicle was driven through water. The scan tool displayed DTC B16F912. Inspection revealed water inside the driver's side seatbelt pretensioner connector (located beneath the B-pillar). Electrochemical corrosion on the terminals caused a short circuit between the signal and power terminals. The technician cleaned the connector with electronic contact cleaner, dried it thoroughly, applied conductive paste, and reinstalled it. After clearing the fault codes, the system returned to normal. Check the door seals to prevent further water ingress.
BYD DTC AI Analysis

Aftermarket seat heating modification damaged the sensor wiring, causing a short circuit.

✓
The owner fitted an aftermarket passenger seat heating pad, causing the airbag warning light to illuminate. Diagnosis revealed DTC B16F912. Inspection found metal staples used to secure the heating pad harness during the modification had pierced the second signal wire of the factory seat occupancy sensor, shorting it to the heating pad power wire. Resoldered and insulated the damaged sensor wiring with heat-shrink tubing, rerouted the harness properly, removed the metal staples and secured the loom with dedicated harness tape. Fault resolved.
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.