AU
B16A2-00

B16A2-00 indicates an internal fault or performance degradation in the airbag control unit (SRS ECU) — Atto 3

Safety System

B16A2-00 indicates an internal fault or performance degradation in the airbag control unit (SRS ECU).

This is not an external sensor or actuator issue, but an abnormality in the microprocessor, memory chip, power management module, or internal acceleration sensor on the ECU main board.

This fault causes the airbag system to enter a degraded mode or fail completely.

Front airbags, side airbags, and pretensioner seatbelts may fail to deploy normally during a collision.

It may also trigger a high-voltage interlock cut-off, preventing the vehicle from powering up or causing a loss of high voltage while driving.

This DTC is a Hard Fault.

Simply disconnecting the power usually cannot clear it.

Perform an in-depth diagnosis of the hardware or software status.

The B16A2-00 fault code on the Atto 3 indicates an internal failure within the airbag control unit (SRS ECU), affecting its microprocessor or internal sensors. This medium-severity issue can prevent airbags and seatbelt pretensioners from deploying during a crash, and may cut high-voltage power. It is typically caused by aged circuit board components or power supply problems. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Aged or damaged components on the SRS ECU internal circuit board (such as bulging electrolytic capacitors or cold solder joints on the main control chip)
  • 2Abnormal power supply (unstable battery voltage, excessive voltage drop in the ECU power supply circuit, ground point oxidation causing reference voltage drift)
  • 3Uncleared ECU internal trigger record after a vehicle collision, or a short circuit in the crash sensor circuit causing ECU self-protection.
  • 4Software/calibration data corruption (flash memory fault, interrupted flashing, calibration data checksum failure)
  • 5ECU internal acceleration sensor (MEMS) zero-point drift due to extreme environmental conditions, or signal processing circuit fault.
What To Do
  • 1
    Use the VDS2000/VDS3000 diagnostic tool to read the complete DTC list, check for accompanying communication or power supply fault codes such as B16A3 and B1650, and record the freeze frame data.
  • 2
    Check the SRS ECU power supply (constant +B, ignition switch IG1) and ground (G10A/G10B) voltages. Standard value: 12V±0.5V. Check fuse SB02/FB14 (depending on vehicle model).
  • 3
    Measure diagnostic CAN-H (pin 6) and CAN-L (pin 14) line voltage (approximately 2.5V) and terminating resistance (60Ω) to rule out false faults from communication interference.
  • 4
    Perform the SRS system self-check cycle (cycle the ignition switch ON → OFF three times) and observe if the fault code becomes intermittent. If the fault is current, attempt to update the ECU software (if a new version is available) or reflash the calibration data.
  • 5
    Disconnect the battery negative terminal for 5 minutes, then remove and inspect the SRS ECU (usually located under the center console or behind the armrest). Check the exterior for water ingress or burn marks, and test the internal capacitor for a short circuit.
  • 6
    If the above checks are normal, replace the SRS ECU with a unit of the same part number. Perform Online Coding, Configuration, and airbag system Zero Point Calibration.
  • 7
    Perform system function verification: simulate a collision test (trigger a virtual signal using special equipment), check the seat belt pretensioner resistance value, and confirm the instrument cluster airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV300: Intermittent airbag warning light while driving, DTC B16A2-00.

✓
The airbag warning light came on intermittently during normal driving. Retrieved DTC B16A2-00 (current). Inspection found the vehicle had aftermarket audio installed; removing the centre console had caused pin 15 (power) of the SRS ECU connector (KJB01) to partially back out, causing intermittent power loss. Re-crimped the pin and applied conductive grease. Fault resolved. ECU not replaced — this was a false ECU fault caused by poor terminal contact.
BYD DTC AI Analysis

Qin 100 SRS ECU locked after accident repair

✓
The vehicle sustained a front-end collision. The airbags did not deploy, but the impact damaged the front impact sensor. After repairs, the airbag warning light remained on in the instrument cluster. Retrieved DTCs B16A2-00 and B1650-00 (Collision Record Latched). Inspection found that the SRS ECU had recorded the collision event, but the trigger voltage did not reach the deployment threshold, causing the ECU to enter Crash Mode. Attempted the Crash Data Clear procedure per the workshop manual, but it failed. Diagnosed physical damage to the ECU internal memory. Replaced the SRS ECU with a new unit (Part No. BYD-3636100-XS), performed online coding and system calibration. Fault resolved.
BYD DTC AI Analysis

Qin EV450 cannot enter Ready mode, with DTC B16A2-00 and high-voltage interlock fault.

✓
The vehicle failed to power up. The instrument cluster displayed 'Powertrain Fault' and the airbag warning light stayed on. DTC scanning found both B16A2-00 and P1A3400 (high-voltage interlock fault) at the same time. Found the SRS ECU housing earth wire was not tightened during the accident repair, causing the ECU's internal reference ground to drift. This both misreported an ECU fault and sent a collision signal to the BMS via the CAN bus, triggering the high-voltage shutdown. After tightening the earth wire and clearing the fault codes, the vehicle returned to normal operation. No ECU replacement necessary.
BYD DTC AI Analysis

Qin 80 software version defect caused B16A2-00 false positive

✓
In multiple complaint cases, the 2017 Qin 80 frequently logged DTC B16A2-00 during startup in low-temperature environments (below -10°C), with the fault clearing once the vehicle warmed up. BYD Technical Service Bulletin TSB-SRS-2018-03 confirmed early SRS software versions (below V1.02) had an overly sensitive internal accelerometer self-check at low temperatures. Solution: Upgraded the SRS ECU software to V1.05 to optimise the self-check thresholds. The fault has not reappeared since the upgrade, and no hardware replacement was necessary.
BYD DTC AI Analysis

Qin EV300 SRS ECU internal short circuit after wading through water.

✓
After the vehicle waded through water, multiple warning lights came on the instrument panel. Retrieved DTCs including B16A2-00, U0140 (lost communication with BCM), etc. Disassembly and inspection found water ingress at the SRS ECU mounting location (floor centre tunnel), with visible water stains and verdigris on the circuit board. Measured a short to ground in the ECU internal power supply module and determined water ingress had caused the internal voltage regulator chip to burn out. Replaced the SRS ECU, re-wrapped the wiring harness, and applied sealant for waterproofing. Fault resolved.
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.