AU
B16BB-00

DTC B16BB-00 indicates the Airbag Control Unit (SRS ECU) internal self-check detected a critical fault — Atto 3

Safety System

DTC B16BB-00 indicates the Airbag Control Unit (SRS ECU) internal self-check detected a critical fault.

This fault involves a hardware-level abnormality in the ECU internal processor, memory module, or power management unit, which may cause the airbag system to fail to deploy during a collision or deploy unintentionally in non-collision situations.

This DTC indicates a permanent hardware fault that a simple code clear usually cannot resolve.

Thoroughly inspect the ECU power supply stability, CAN communication integrity, and internal circuit board condition.

In BYD Qin series vehicles, this ECU integrates crash decision algorithms and multi-point sensor data processing functions.

The fault triggers the system to enter safety protection mode, disabling airbag deployment for safety.

The B16BB-00 fault code on the Atto 3 indicates a medium-severity internal fault in the Airbag Control Unit. It may involve damaged ECU memory, processor hardware, or unstable power/ground supply, which can affect airbag operation. This is usually not fixed by simply clearing the code. The recommended fix is to visit an authorised dealer for SRS ECU, power supply, ground, and communication checks. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1SRS ECU internal memory or processor hardware damage, typically due to internal circuit failure from voltage fluctuations, overheating, or component aging.
  • 2Abnormal power supply, including excessive contact resistance in the +B power supply circuit, a loose ground terminal, or unstable battery voltage causing an ECU reset.
  • 3CAN bus communication fault, such as a short circuit, open circuit, or electromagnetic interference in the powertrain CAN or dedicated airbag CAN wiring, preventing normal ECU communication.
  • 4Corrupted software calibration data resulting from a previous incomplete flash, electromagnetic interference, or long-term memory bit flip.
  • 5Short circuit in the external crash sensor or wiring harness causes the ECU to detect abnormal current and enter protective fault mode.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000 or ED400) to read the complete fault code stream, record freeze frame data, and check for accompanying communication fault codes (such as codes starting with U).
  • 2
    Check the SRS ECU power supply: Measure the voltage at the ECU connector +B terminal (should be a stable 9-16V), check the ground harness resistance (should be less than 1Ω), and verify the power supply waveform has no abnormal pulses.
  • 3
    Check CAN bus communication: Measure CAN-H and CAN-L line voltages (normally around 2.5 V, differential voltage 2 V), check terminating resistance (around 60 Ω), and use an oscilloscope to check the waveform for distortion.
  • 4
    Perform a software flash: Update the calibration data or reinstall the SRS ECU software. If the fault code persists after flashing, diagnose as a hardware fault.
  • 5
    Replace SRS ECU: Disconnect the negative battery terminal, wait 90 seconds for the capacitor to discharge, then remove and install a new airbag control unit.
  • 6
    Coding and configuration: Use the diagnostic tool to write the VIN to the new ECU, code the vehicle configuration, and calibrate sensor parameters.
  • 7
    System verification: After clearing the fault code, perform an SRS system self-check and a simulated crash signal test (using the diagnostic tool). Verify all airbag circuit resistances are normal (2-3Ω).
Real-World Cases
BYD DTC AI Analysis

Airbag warning light stayed on while driving the Qin EV300. Replacing the ECU fixed it.

✓
A 2017 Qin EV300 with 85,000 km on the clock suddenly showed the airbag warning light. The technician used a VDS diagnostic scanner to retrieve fault code B16BB-00, which would not clear. The ECU supply voltage measured 12.4V (normal), and the CAN bus communication waveform showed no abnormalities. The technician attempted a software reflash, but the fault persisted. Disassembly revealed obvious burn marks on the SRS ECU internal circuit board, indicating the internal power management chip had failed. The technician replaced the SRS ECU with a new unit and performed coding and matching. The system passed self-test. The warning light went out, and a road test was normal.
BYD DTC AI Analysis

After accident repair, the Qin 80 triggered DTC B16BB-00. A software reflash fixed it.

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We replaced the front bumper and left collision sensor following a minor front-end collision on this 2017 Qin 80. The airbag warning light came on the dash the day after delivery. The scan tool showed code B16BB-00 and a left sensor communication fault. We confirmed the replacement sensor model was correct and the wiring harness was properly connected. Suspecting the impact had corrupted the ECU internal data, we reflashed the calibration data to the SRS ECU. The fault codes cleared and the system returned to normal operation—no hardware replacement was needed.
BYD DTC AI Analysis

Intermittent DTCs on Qin EV450 caused by loose connection in power supply line

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2018 BYD Qin EV450. The customer reported the airbag warning lamp occasionally illuminates but goes out after a restart. Historical DTC B16BB-00 was present. Inspection found the ECU power connector +B terminal was slightly oxidized and loose. Dynamic voltage dropped below 8V during hard acceleration. Further inspection revealed a poor connection between the battery positive terminal and the main power cable. After repairing the power contact and installing fastening washers, voltage is stable at 13.8V; the fault has not reappeared.
BYD DTC AI Analysis

Qin 100: SRS system inoperative after wading; ECU internal short circuit.

✓
A 2017 Qin 100 developed multiple safety system warning lights on the instrument panel after driving through water. Diagnosis found the SRS ECU would not communicate and had set DTC B16BB-00 (hardware fault). Inspection found the ECU located under the passenger floor. Water ingress from wading caused internal corrosion and multiple short circuits on the circuit board. Replaced the ECU with a new unit, resealed the mounting location, and checked the related wiring harness insulation. System functions returned to normal after repair. Recommend checking the vehicle's wading depth history.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 overview →
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.