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B16A2-00

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

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 Qin Plus indicates an internal fault within the airbag control unit affecting its processor, memory, or sensors. This medium severity issue may prevent airbags and seatbelt pretensioners from deploying in a crash and can cut high-voltage power. Causes include aged circuit board components or unstable power supply. Visit an authorised dealer for hardware diagnosis and repair. Typical repair cost data is available from 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Aged or damaged components on the SRS ECU internal circuit board (e.g., 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 circuit, oxidized ground point causing reference voltage drift)
  • 3Uncleared internal ECU trigger record after a vehicle collision, or a short circuit in the crash sensor circuit causing ECU self-protection.
  • 4Software/calibration data corrupted (Flash memory fault, program flashing interrupted, calibration data checksum failure)
  • 5Internal ECU accelerometer (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 power +B, ignition switch power IG1) and ground (G10A/G10B) voltage. Standard value: 12V ± 0.5V. Check fuse SB02/FB14 (depending on vehicle model).
  • 3
    Measure the diagnostic CAN-H (pin 6) and CAN-L (pin 14) line voltages (approx. 2.5V) and terminal resistance (60Ω) to rule out false codes caused by communication interference.
  • 4
    Perform the SRS system self-check cycle (ignition switch ON→OFF three cycles) and observe if the fault code changes to intermittent. If the fault is current, update the ECU software (if a new version is available) or reflash the calibration data.
  • 5
    Disconnect the 12V 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 show no abnormalities, replace the SRS ECU with one of the same part number. Perform Online Coding, write Configuration parameters, and perform airbag system Zero Point Calibration.
  • 7
    Verify system function: simulate a collision test (use special equipment to trigger a virtual signal), check the seat belt pretensioner resistance, and confirm the instrument cluster airbag warning light turns off.
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 Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.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.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.