AU
B16A2-00

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

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.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Aged or damaged SRS ECU internal circuit board components (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 internal ECU 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 program flashing, calibration data checksum failure)
  • 5Internal ECU 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 power +B, ignition switch IG1) and ground (G10A/G10B) voltages. The standard voltage is 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 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 remains 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 box). Inspect 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 one of the same part number. Perform Online Coding, Configuration parameter writing, and airbag system Zero Point Calibration.
  • 7
    Perform system function verification: simulate a collision test (use dedicated equipment to trigger a virtual signal), 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 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.