AU
B16BD-00

DTC B16BD-00 indicates a LIN (Local Interconnect Network) bus communication fault between the Body Control Module (BCM) and the left front window motor — Seal U

Safety System

DTC B16BD-00 indicates a LIN (Local Interconnect Network) bus communication fault between the Body Control Module (BCM) and the left front window motor.

Some early documents label this code as SRS-related; however, it actually indicates a loss of communication or abnormal signal voltage at the left front window motor (LHD Driver Door Motor).

The LIN bus uses a single-wire circuit (typically green/white) with a normal operating voltage of 9-11V.

The BCM sets this DTC if it fails to receive a response signal from the motor within the specified time, or if it detects a bus open, short to ground, or short to power.

This fault disables left front window operation and the anti-pinch function.

The BCM may also enter protection mode and cut power to the motor.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1A shorted or burnt-out LIN transceiver chip inside the front left window motor pulls the bus voltage low (commonly 2-3V).
  • 2Poor contact or break in the LIN wiring harness at the door hinge (repeated door opening and closing causes copper strand fatigue fracture, leaving only a few strands connected).
  • 3Aged or failed motor connector waterproof seal allows rain or car wash water ingress, causing connector oxidation and a LIN line short to ground.
  • 4Blocked door drain hole allows accumulated water to soak the motor, causing corrosion or a short circuit in the internal communication circuit.
  • 5Motor mechanical binding (steel cable corrosion, mud and sand accumulation in the guide rails) causes excessive stall current; the BCM cuts communication for protection and logs the fault.
What To Do
  • 1
    Connect the BYD VDS diagnostic tool, enter the BCM system to read fault codes, confirm whether B16BD-00 is a current or history fault, and record the freeze frame data.
  • 2
    Check the condition of the left front window motor power supply (constant 12V, connector pin 1) and ground (connector pin 2) to rule out basic circuit faults.
  • 3
    Disconnect the motor connector and measure the LIN line (pin 3) voltage. Normal voltage is 9-11 V. If the voltage is below 5 V, measure the resistance to ground. Normal resistance is greater than 10 kΩ.
  • 4
    Check the wiring harness sleeve at the door hinge. Specifically inspect the LIN wire (green/white) for breaks or poor connections. If necessary, strip back the sleeve to inspect the internal copper strands.
  • 5
    Remove the door trim panel and check the motor connector seal. Inspect the pins for green oxidation or water stains. If present, clean the pins, replace the waterproof sealing ring, and apply waterproof silicone grease.
  • 6
    Reconnect the connector and use an oscilloscope to measure the LIN bus waveform. Verify the data frame interval and waveform amplitude are normal, or replace with a test motor to verify.
  • 7
    If suspecting mechanical binding, measure the motor operating current: normal lift current is 3-6A. If the current exceeds 12A and the motor emits a burnt smell, replace the window regulator assembly.
  • 8
    After repair or replacement, clear the fault code and perform the window anti-pinch initialization: fully raise the window glass and hold for 2 seconds, then fully lower it and hold for 2 seconds. Verify normal operation.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: Motor internal short circuit dragging down voltage

✓
2019 Qin Pro DM – driver's side window suddenly stopped working; the other three doors were unaffected. Scanned the BCM and found DTC B16BD-00 (left front window motor communication fault). Measured LIN line voltage at the motor connector: only 2.8V (normal 9–11V). Disconnected the motor connector, and the voltage recovered to 10.2V. Determined that the internal LIN chip in the motor had shorted, pulling the bus low. Replaced the left front window motor assembly (SA2H-6104210) and performed anti-pinch initialisation. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Water ingress and oxidation in the Han EV connector caused communication failure.

✓
2020 Han EV left front window stopped midway with a clicking noise, occurring frequently in wet weather. DTC B16BD-00 stored as both current and history. Power and ground tested normal. Oscilloscope check showed noise on the LIN bus waveform. Disassembly revealed green copper oxide inside the motor connector; the waterproof seal had aged and was leaking. Removed the oxidation, replaced the seal and applied waterproof silicone grease. The motor had minor water ingress, so replaced it (SC2E-6104210). Followed up for one week with no recurrence.
Original source ↗
BYD DTC AI Analysis

Song PLUS DM-i door water ingress burned out communication chip

✓
2021 Song Plus DM-i: Left front window wouldn't go up after a car wash. Scan tool showed B16BD-00 (lost communication with left front window motor). Removed the door trim and found blocked drain holes. Water had accumulated and soaked the motor. Measured LIN line-to-ground resistance at only 45 Ω (normal >10 kΩ), indicating the motor's internal communication chip had burned out. Unclogged the drain holes, dried the wiring harness, replaced the motor assembly, and installed a waterproof protective sleeve.
Original source ↗
BYD DTC AI Analysis

Tang DM intermittent poor contact in hinge wiring harness

✓
2018 Tang DM left front window malfunctions intermittently on rough roads; fault is intermittent. DTC B16BD-00 stored as intermittent. Power and earth normal; fault recurs when wiggling the harness. Stripped back the rubber boot at the door hinge and found the LIN wire (green/white) internal copper conductors 95% fractured, with only a minimal connection remaining, causing communication dropouts under vibration. Cut out the fractured section, soldered in a 0.5mm² automotive-grade jumper wire, sealed with heat-shrink tubing, then rerouted and secured the harness.
Original source ↗
BYD DTC AI Analysis

e5 ride-hailing vehicle motor mechanical seizure and locked rotor

✓
2017 BYD e5 (commercial vehicle). Left front window slowed then jammed; could be pushed manually, motor dead with a burning smell. Read DTCs B16BD-00 and B16BD-11 (motor circuit low voltage). Measured motor current at 14.5A (normal 3–6A), diagnosed mechanical binding (cable corroded). Replaced left front window regulator assembly (motor and cable, P/N SA2A-6104210), cleaned mud from the guide rails, and applied rubber protectant. Current dropped to normal 4.2A.
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.