AU
B16DF-00

This fault code indicates the SRS (airbag) control unit detects a communication interruption or no connection with the Left Rear Impact Sensor — Seal U

Safety System

This fault code indicates the SRS (airbag) control unit detects a communication interruption or no connection with the Left Rear Impact Sensor.

This sensor typically mounts in the vehicle’s left rear side panel, C-pillar, or rear door area to monitor side-impact acceleration signals.

The SRS ECU triggers this fault if it fails to receive valid data from the sensor within a predetermined time, or if it detects circuit resistance outside the normal range (open or short circuit).

This fault disables the vehicle’s side-impact detection function.

The system may fail to accurately determine collision severity, suppressing normal deployment of the left rear side airbag/side curtain airbag.

In some cases, this creates a risk of unintended airbag deployment in fail-safe mode.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Broken or crushed left rear impact sensor wiring harness, especially at bends passing through the door hinge or inside the sill trim panel where long-term vibration fractures the copper wires.
  • 2Loose sensor connector, backed-out pin, or water ingress and corrosion. Driving through water or poor sealing after a car wash commonly causes terminal oxidation.
  • 3Internal crash sensor accelerometer damage or circuit fault causes no signal output.
  • 4SRS control unit internal detection circuit fault preventing correct sensor signal identification (less common)
  • 5Wiring harness accidentally cut or connector not fully seated during accident repairs or vehicle modifications (such as window tinting or audio system installation).
What To Do
  • 1
    Connect the dedicated BYD diagnostic tool (VDS or ED400), read the complete fault codes and freeze frame data, and confirm the vehicle speed, timestamp, and other information at the time the fault occurred.
  • 2
    Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds for the SRS system high-voltage capacitor to fully discharge.
  • 3
    Remove the left rear interior trim panel (lower C-pillar trim panel or left rear door sill trim panel) and locate the left rear impact sensor (usually marked 'LEFT REAR' or 'LR').
  • 4
    Check the sensor connector for looseness or backed-out pins. Inspect the terminals for green corrosion or water marks. If necessary, clean the terminals with electrical contact cleaner and apply conductive grease.
  • 5
    Use a multimeter to measure sensor wiring harness continuity: check the circuit resistance between the sensor connector and the SRS ECU (should be less than 1Ω), and check the insulation resistance to ground (should be greater than 1MΩ).
  • 6
    Measure the sensor body resistance (refer to the workshop manual for the standard value, typically 2-5 kΩ). If the resistance is infinite or zero, replace the sensor.
  • 7
    If the wiring harness is damaged, repair or replace it. Protect the harness with high-temperature corrugated conduit to prevent rubbing against metal body edges.
  • 8
    Reconnect all connectors, reconnect the battery negative terminal, turn the ignition ON, use the diagnostic tool to clear the fault code, and perform an SRS system self-diagnosis.
  • 9
    Perform a road test or simulated vibration test to confirm the fault code does not recur, and check if the instrument panel airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Qin EV450 left rear impact sensor fault after wading

✓
A 2018 BYD Qin EV450 came in with the airbag warning light on the instrument panel constantly on. Connected a VDS diagnostic scanner and retrieved DTC B16DF-00 (left rear impact sensor disconnected). Inspection found the left rear door had been exposed to water. Removed the left rear sill trim panel and found the impact sensor connector had visible water stains and copper oxide corrosion inside. Cleaned the connector terminals, dried the wiring harness with compressed air, applied waterproof sealant and reconnected the plug. Cleared the fault code and the system returned to normal operation.
BYD DTC AI Analysis

Loose sensor connection on BYD Qin 100 after accident repair

✓
2017 BYD Qin 100. The SRS warning light illuminated following right rear collision repairs. Diagnosis revealed DTC B16DF-00. Inspection found the left rear impact sensor connector was not fully seated during the repair disassembly, causing an intermittent connection from driving vibrations. Reseated connector and installed a retaining clip, then secured the wiring harness routing with cable ties. Fault resolved.
BYD DTC AI Analysis

Suspected B16DF-00 high-voltage battery contact fault case

✓
An EV reported DTC B16DF-00. The technician suspected abnormal resistance at the high-voltage battery front-end contacts and recommended checking the battery balancing status and front-end contact connections. Note: This case differs from the standard SRS sensor definition, possibly due to model year variations in DTC definitions or a false report by the battery management system under specific conditions.
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.