AU
B16DF00

This DTC indicates an interrupted communication link between the airbag control unit (SRS ECU) and the left rear crash sensor — Seal U

Safety System

This DTC indicates an interrupted communication link between the airbag control unit (SRS ECU) and the left rear crash sensor.

The left rear crash sensor typically utilizes a MEMS capacitive accelerometer and mounts on the left rear side panel (C-pillar area) to monitor left rear collision acceleration.

During the ECU initialization self-check or a drive cycle, if the ECU fails to detect the sensor bias voltage (normally a 2.5V reference voltage at a 2-3kΩ equivalent resistance), detects infinite circuit resistance, or reads a continuous high or low signal line voltage exceeding the threshold, it registers a 'not connected' state.

This fault may prevent the left rear side airbag and curtain airbag from deploying correctly during a collision.

The ECU simultaneously illuminates the airbag warning lamp and enters fail-safe mode (some models disable the entire side airbag circuit).

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose sensor wiring harness connector, backed-out pin, or oxidation from water ingress (common when failing to fully seat the connector after rear seat removal/installation or C-pillar trim repairs).
  • 2Physical damage to the wiring harness causing an open circuit (sill trim pinching the wiring, detached harness retaining clips rubbing against sharp body edges and breaking the copper strands)
  • 3Internal damage to the crash sensor body (cracked piezoelectric element, internal resistance drift outside the standard 1.8-3.5kΩ range)
  • 4Installed a mismatched aftermarket sensor after accident repairs (incorrect configuration code, or 2-wire/3-wire mix-up causing an incompatible communication protocol).
  • 5Corrosion of the left rear sill wiring harness from prolonged water immersion (common in flooded vehicles, causing green corrosion on connector terminals or internal open circuits)
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge the SRS capacitor residual charge and prevent accidental airbag deployment.
  • 2
    Fault Confirmation: Use the genuine BYD diagnostic tool (ED400/ED600) to read the fault codes, verify B16DF00 is a Current DTC, and record the freeze frame data.
  • 3
    Location and inspection: Remove the left rear C-pillar interior trim panel or left rear door sill trim panel. Locate the left rear crash sensor (usually located above the left rear door striker or on the side panel reinforcement beam).
  • 4
    Basic measurement: Disconnect the sensor connector and measure the resistance between the two terminals on the sensor body (standard: 2-3kΩ). If the resistance is infinite or 0Ω, replace the sensor.
  • 5
    Wiring harness inspection: Measure the wiring continuity (must be less than 1Ω) and insulation resistance to ground (must be greater than 10MΩ) between the sensor connector and the SRS ECU (usually located under the center console). Focus on the bent sections of the sill wiring harness.
  • 6
    Repair: Repair the damaged wiring harness (solder and heat shrink tubing) and re-wrap with waterproof tape. If the connector is oxidized, clean with electrical contact cleaner and apply conductive paste.
  • 7
    Replacement and installation: If the sensor is damaged, replace it with a genuine part (part number must match the VIN). Tighten to 8-10 N·m during installation to prevent loosening from vibration.
  • 8
    System reset: Connect the battery, use the diagnostic tool to clear the fault code, and perform an SRS system self-check (some models require crash sensor configuration learning or online calibration).
  • 9
    Verification test: Road test the vehicle for 5–10 km, including bumpy roads. Confirm the SRS warning lamp remains off and the diagnostic tool shows no history fault codes.
Real-World Cases
BYD DTC AI Analysis

Yuan PLUS EV rear seat removal and installation caused a loose sensor connector.

✓
The SRS warning light stayed on. The scan tool read DTC B16DF00. Inspection found the sensor connector inside the left rear C-pillar trim panel was loose. The wiring harness had been pulled during rear seat removal and installation, causing a poor connection. Sensor resistance was infinite. Reconnected the connector, secured the harness routing with cable ties, cleared the fault code, and the system returned to normal.
Original source ↗
BYD DTC AI Analysis

Qin Pro DM door sill trim pinched wire, causing wiring harness chafing and short circuit

✓
SRS warning light illuminated intermittently while driving, with stored DTCs B16DF00 and B16E011. Inspected left rear sill trim and found wiring harness pinched by a retaining clip, insulation worn through exposing copper strands that shorted to body ground. Repaired damaged harness and adjusted routing, replaced deformed sensor mounting bracket. Monitored for one week with no recurrence.
Original source ↗
BYD DTC AI Analysis

Incorrect aftermarket sensor configuration on Song PLUS after accident repair

✓
After rear-end collision repair on the left rear, the SRS warning light stayed on. Pulled DTC B16DF00. The shop had installed an aftermarket 2-wire sensor; the vehicle needs a 3-wire accelerometer. Sensor resistance was only 0.8 kΩ, well below spec. Replaced it with the correct OEM sensor and ran the configuration learn procedure using a scan tool. Fault 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.