AU
B16A2

DTC B16A2 indicates the airbag control unit (SRS ECU) detects an internal fault or system-level communication error — Atto 3

Safety System

DTC B16A2 indicates the airbag control unit (SRS ECU) detects an internal fault or system-level communication error.

As the core control module of the passive safety system, the SRS ECU monitors crash sensor signals, deploys airbags and seat belt pretensioners, and executes post-collision fuel cut-off protection.

This DTC indicates an anomaly in the ECU internal processor, memory, or communication interface.

It also triggers upon detecting a power/ground circuit fault, CAN bus communication interruption, or crash data lock (incorrectly reset after a collision).

This fault may prevent the airbag system from deploying during an actual collision or cause related functions, such as seat belt pretensioners and seat occupancy detection, to fail.

This severe fault compromises driving safety.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Abnormal SRS ECU power supply: Includes low battery voltage (<9V), blown dedicated fuse (usually located in the dashboard fuse box or front compartment power distribution box), or loose or corroded power supply circuit.
  • 2Ground circuit fault: ECU ground point is loose, oxidized, or has excessive contact resistance (>1Ω), causing unstable control unit operation.
  • 3CAN bus communication fault: SRS ECU lost communication with the vehicle network (powertrain CAN or comfort CAN). Possible causes include a wiring short circuit, open circuit, or abnormal terminating resistor.
  • 4Internal ECU hardware damage: Voltage fluctuations, water ingress, or aging typically damage the control unit's internal processor, memory (EEPROM/Flash), or crash sensor interface circuit.
  • 5Crash data locked: The vehicle experienced a collision. After recording the collision event, the ECU enters a locked state (Crash Locked). Use a dedicated diagnostic tool to execute the 'Crash Data Clear' and 'ECU Unlock' procedures.
What To Do
  • 1
    Step 1: Use the BYD dedicated diagnostic tool (VDS2000/6000) to access the SRS system, read the complete fault codes and freeze frame data, check for accompanying fault codes (such as B16A0, B16A1, etc.), and view the 'collision history record' data stream to confirm if the vehicle experienced a collision.
  • 2
    Step 2: Check the SRS ECU power supply circuit. Disconnect the negative battery terminal, wait 3 minutes, and unplug the ECU connector. Measure the voltage from the ECU connector power pins (constant power +B, ignition switch IG) to ground and check fuse continuity. Verify the voltage is 9-16V. Measure the resistance from the ground pins to ground; it must be <1Ω.
  • 3
    Step 3: Check the CAN communication circuit. Measure the voltage to ground at diagnostic connector pin 6 (CAN-H) and pin 14 (CAN-L) (normal: 2.5-3.5V and 1.5-2.5V) and the terminal resistance (approximately 60Ω). Check the CAN wiring harness from the SRS ECU to the gateway for open or short circuits.
  • 4
    Step 4: Visual and connection inspection: Check the SRS ECU mounting position (usually under the centre console or in front of the gear selector) for water stains or impact marks. Check all airbag, seat belt pretensioner, and crash sensor connectors for secure connection. Measure the resistance of the relevant sensors (normal: 2-3 Ω).
  • 5
    Step 5: Software and calibration procedures: If wiring is normal, attempt 'online programming' or 'software upgrade' on the SRS ECU. If the vehicle has a collision history, perform 'collision data clearing' and 'system configuration writing'. After replacing the ECU, perform 'VIN writing' and 'safety system calibration'.
  • 6
    Step 6: Verification test: Clear the fault code, cycle the ignition switch 3 times, and confirm the fault code does not reappear. Perform the 'SRS system self-check' function, confirm all airbag and sensor statuses display normally, and verify the instrument panel airbag light is off.
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX Airbag Sensor Communication Fault

✓
Symptoms: The airbag warning light on the instrument panel stayed on. A diagnostic scan revealed body control fault codes (B16XX series). The vehicle was in a collision; the airbags did not deploy, but the system logged a fault. Diagnosis: Connected a dedicated diagnostic tool and retrieved a fault code for airbag sensor communication failure. Checked the airbag control module supply voltage (12V – normal). Inspected CAN bus communication lines and found the passenger-side crash sensor connector loose. Measured the sensor resistance – it read outside the standard 2–3 Ω range. Resolution: Disconnected, cleaned, and reconnected the crash sensor connector. Performed the 'airbag system calibration' procedure with the dedicated diagnostic tool. Cleared fault codes, test drove the vehicle, and the warning light went out.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro seat belt pretensioner control circuit fault

✓
Symptoms: After starting the vehicle, the instrument cluster displayed “Check SRS System”. The fault codes would not clear with a standard OBD scanner, and the seatbelt warning light flashed. Diagnosis: Connected a Launch X431 scan tool and accessed the airbag system. Retrieved a fault for the driver’s side seatbelt pretensioner control circuit. Removed the B-pillar trim to inspect the seatbelt pretensioner connector and found oxidised pins inside. Measured the pretensioner resistance: 5.8Ω (standard value: 2.0–3.0Ω). Resolution: Replaced the driver’s side seatbelt assembly (including pretensioner) and reconnected the connector. Used the scan tool to perform “Seat Occupancy Sensor Calibration” and “SRS System Self-Test”. Cleared fault codes. System returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM airbag control module VIN mismatch fault

✓
Symptoms: After accident repairs, the airbag warning light stayed on. Fault codes showed communication interruption or data error with the airbag module. Diagnosis: Checked the airbag control unit (ACU) power and ground circuits — normal. Checked CAN-H and CAN-L line voltages (CAN-H 2.7V, CAN-L 2.3V — normal). Found the aftermarket ACU installed during accident repair did not match the vehicle VIN, causing the system to report the fault. Resolution: Replaced the ACU with a genuine unit. Performed ECU online matching and safety system configuration write using the BYD dedicated diagnostic tool. Executed the crash data clear procedure. Resolved the fault.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.