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B16B0

DTC B16B0 indicates the Airbag Control Unit (SRS ECU) internal self-diagnosis detected a critical function abnormality — Atto 3

Safety System

DTC B16B0 indicates the Airbag Control Unit (SRS ECU) internal self-diagnosis detected a critical function abnormality.

This ECU integrates the main control MCU, backup power supply, crash sensors (accelerometers), and ignition driver circuit.

An "internal fault" specifically refers to compromised ECU core hardware or firmware integrity, including internal voltage regulator module failure (e.g., 5V/3.3V reference voltage deviation), EEPROM data checksum errors, interrupted communication between the main and backup CPUs, crash sensor signal processing circuit faults, or ignition loop driver chip damage.

This fault forces the airbag system into fail-safe mode.

During a collision, the system may fail to deploy airbags or activate seat belt pretensioners.

It also carries a risk of unintended deployment, classifying it as a highest-level safety-related fault.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1ECU internal power management chip failure: Prolonged battery depletion or voltage surges (such as reversed polarity during jump-starting) burn out the ECU internal DC-DC converter or voltage regulator module, preventing stable operating voltage supply to the main control chip.
  • 2Acceleration sensor (MEMS) fault: The crash sensor integrated inside the ECU exhibits zero-point drift, a stuck-high/low signal, or an SPI communication fault, causing the ECU to determine a loss of its sensing capability.
  • 3Software/firmware corruption: Electromagnetic interference, interrupted programming, or physical aging of the Flash memory causes calibration data or control algorithm checksum errors.
  • 4PCB solder joint fatigue: Long-term vibration (e.g., driving on rough roads) cracks solder balls on BGA-packaged chips inside the ECU or fractures through-hole plating, resulting in intermittent poor contact.
  • 5Thermal damage or liquid ingress: Air conditioning condensate soaking the ECU at its mounting position (such as beneath the center console) or high-temperature exposure causes internal capacitor leakage, copper foil corrosion, or integrated circuit thermal breakdown.
What To Do
  • 1
    Initial diagnosis: Use the BYD VDS2000/VDS1000 diagnostic tool to read all DTCs. Confirm if B16B0 is a current (Active) code and check for accompanying codes (e.g., B16B1, U0151). Record freeze frame data (vehicle speed, timestamp, battery voltage) and check if the instrument cluster SRS warning light remains illuminated.
  • 2
    External factor troubleshooting: Disconnect the battery negative terminal and wait 3 minutes. Check the SRS ECU wiring harness connector (usually located under the center console or in front of the gear selector) for oxidation or backed-out pins. Measure the constant power (B+) and ignition switch power (IG1) voltages, and verify the ground wire resistance is <1Ω. Measure the CAN-H and CAN-L line voltages (approximately 2.5V) and terminating resistance (approximately 60Ω) to rule out misdiagnosis caused by external power or communication faults.
  • 3
    ECU hardware inspection: Remove the SRS ECU and inspect the casing for physical damage, water stains, or burn marks. Power the ECU (12V) using a dedicated power supply simulator and measure the quiescent current (should be <50mA; >200mA indicates an internal short circuit). If available, use an X-ray or microscope to inspect the solder joints of the capacitors, inductors, and main control chip on the PCB.
  • 4
    Software repair attempt: If the hardware is visually normal, use the diagnostic tool to perform an 'ECU software upgrade' or 'configuration parameter refresh'. Calibration data loss causes some B16B0 faults. Rewriting the VIN, vehicle configuration codes (such as airbag quantity and seat occupancy sensor type), and crash threshold parameters may clear the fault.
  • 5
    Replacement and matching: If diagnostics confirm an internal hardware fault, replace the SRS ECU with a unit of the same Part Number. Perform the following on the new ECU: ① Immobilizer matching (write the VIN); ② System configuration (activate the corresponding ignition circuits based on the actual vehicle configuration); ③ Seat occupancy sensor calibration (if applicable); ④ Steering angle sensor zero-point calibration (some models integrate the yaw rate sensor into the SRS ECU).
  • 6
    Verification Test: After completing the repair, clear the fault code and perform a system self-check (turn the key to ON, wait 6 seconds, and observe if the SRS warning lamp turns off). Use the diagnostic tool to perform the 'Crash Sensor Test' (simulated signal input test) and the 'Ignition Circuit Resistance Test' (check continuity of each airbag and pretensioner circuit; normal value: 2-3 Ω). Finally, perform a road test to verify no intermittent faults recur.
Real-World Cases
BYD DTC AI Analysis

2019 Song MAX SRS ECU internal power supply module burned out

✓
Customer reported the SRS warning light on the instrument cluster stayed on constantly. Scan tool retrieved DTC B16B0. Vehicle history showed the battery went flat and was jump-started a week earlier, possibly with reverse polarity. Removed and inspected the ECU; found the internal fuse blown and pin 12 of the power management chip (TLE7368) burnt. Reverse voltage breakdown had shorted the 5V regulator output. Replaced the SRS ECU (part number BYD-3638100) and reconfigured — fault cleared. Advised the customer to check the jump-start procedure.
BYD DTC AI Analysis

Internal ECU corrosion in flood-damaged BYD Qin Pro DM

✓
After driving through water, the dash displayed 'Check Airbag System'. Read fault codes B16B0 and B16B1. Removed the SRS ECU from the centre of the floor and found the housing seal had deteriorated, allowing water in. The PCB showed multiple areas of copper trace corrosion and bulging capacitors. Cleaned and attempted to dry the unit, but the fault persisted. Determined the internal accelerometer signal conditioning circuit had corroded open. Replaced the ECU and treated the water stains on the wiring harness. Fault resolved. Recommend checking the A/C drain tube for blockage.
BYD DTC AI Analysis

Petrol Qin software version defect causing false positives

✓
2020 Qin petrol variant, no accident history or water ingress. SRS light came on intermittently, pulled intermittent DTC B16B0. Checked ECU power and earth – normal, no external damage. Looked up the TSB (Technical Service Bulletin) and found this ECU batch (hardware version H02, software version V1.03) has an internal watchdog reset defect. Upgraded software to V1.05 and the fault has not reappeared. This is a typical firmware bug, not hardware damage.
BYD DTC AI Analysis

Song MAX internal sensor fault after accident repair

✓
Following front collision repairs (front bumper and left front longitudinal member replaced), the SRS warning light stayed on, storing DTC B16B0. The airbag did not deploy in the original accident, but the ECU likely experienced a high G-force impact. Using a diagnostic scanner, we read the internal acceleration sensor data stream and found the X-axis signal fixed at -12.8g (normal: 0±0.5g), indicating physical damage to the internal sensor. No external cracks were visible, but the MEMS structure had failed. Replacing the ECU and performing collision threshold calibration resolved the issue.
BYD DTC AI Analysis

Long-term vibration caused cold solder joints on the BGA.

✓
A Song MAX rideshare vehicle with 180,000 km on the clock intermittently displayed an SRS warning light; DTC B16B0 came and went. Power supply was normal. Tapping the ECU housing reproduced the fault. We stripped down the ECU and performed BGA rework on the main controller chip (Renesas RH850) using a hot air rework station. After reballing and resoldering, the fault cleared. The root cause was solder joint fatigue from prolonged driving on rough roads. Rideshare operators should regularly inspect the chassis and ECU mounting bracket vibration dampers.
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.