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B16BF

DTC B16BF indicates an internal fault in the airbag electronic control unit (SRS ECU) or a system-level functional failure — Atto 3

Safety System

DTC B16BF indicates an internal fault in the airbag electronic control unit (SRS ECU) or a system-level functional failure.

This fault involves an ECU internal processor self-check anomaly, memory checksum failure, power management module fault, or CAN communication interface fault.

The SRS ECU continuously monitors the internal operating voltage (3.3V/5V regulated output), EEPROM data integrity, watchdog timer status, and communication quality with the vehicle CAN network.

The system sets this DTC when the ECU detects an internal circuit fault, supply voltage outside the 9-16V range, excessive ground resistance (>1Ω), or CAN signal distortion.

This safety-critical fault may cause complete airbag system failure (airbags fail to deploy during a collision), unintended deployment, or seat belt pretensioner failure.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Internal hardware fault in the SRS ECU: damaged main control chip (such as Infineon or Renesas series), aging and leaking electrolytic capacitors, or PCB interlayer short circuit. The ECU housing usually heats up, or the diagnostic tool fails to establish communication.
  • 2Power supply system fault: poor contact of the SRS fuse (usually 10A or 15A) in the instrument panel power distribution box; loose connection causing voltage to drop below 8V; depleted battery or unstable generator output causing ECU reset.
  • 3Ground circuit fault: A loose, oxidized, or paint-covered G101 ground point (located on the instrument panel crossmember or below the A-pillar) causes ground resistance to exceed 5Ω, resulting in ECU operating voltage drift.
  • 4CAN bus communication fault: SRS CAN-H and CAN-L lines shorted to ground, shorted to power, or shorted together; or terminating resistor (120Ω) drift causes signal reflection, preventing the ECU from communicating normally with the BCM and gateway.
  • 5Software/data corruption: Corrupted calibration data in the ECU flash memory, program crash, or version bugs. Commonly occurs after an interrupted vehicle OTA update or improper 12 V battery disconnection.
What To Do
  • 1
    Initial diagnostic scan: Use VDS2000/VDS3000 to access the SRS system. Read the complete fault code list and freeze frame data. Verify if B16BF is a current (Active) fault. Check for accompanying U-class communication fault codes (e.g., U0140, U0151). Record the vehicle status at the time of the fault (voltage, temperature, vehicle speed).
  • 2
    Power and ground measurement: Disconnect the battery negative terminal and wait 90 seconds for the SRS capacitor to discharge. Remove the SRS ECU (usually located under the center console or in front of the gear selector). Measure the voltage to ground at connector pin 1 (constant +B, BATT) and pin 2 (IGN power). The voltage must be 12.0V ± 0.5V. Measure the resistance between the ground pin (GND) and body ground. The resistance must be less than 1Ω. Check the connector for green corrosion or pin back-out.
  • 3
    CAN bus check: Connect an oscilloscope or multimeter to measure diagnostic connector pins 6 (CAN-H) and 14 (CAN-L). Static voltages should be approximately 2.6V and 2.4V respectively. Disconnect the battery and measure the terminal resistance; it should be approximately 60Ω (two 120Ω resistors in parallel). Inspect the wiring harness for chafing against the instrument panel metal bracket, causing an intermittent short circuit.
  • 4
    Substitution verification test: If the wiring is normal, substitute the SRS ECU with a known good unit from the same vehicle model (do not fully install the ECU; simply connect the connector). Observe if the fault code transfers. If the fault disappears, this confirms the original ECU hardware is damaged.
  • 5
    Software update attempt: If hardware tests are normal, use VDS2000 to perform an SRS ECU software update. Select the latest firmware version (verify the version number applies to the specific model year). Maintain stable battery voltage during the update (recommend using a regulated power supply).
  • 6
    Replacement and calibration: If diagnostics confirm an ECU fault, replace the SRS ECU assembly with a new unit (the part number must match the vehicle configuration, such as with or without side and curtain airbags). After installation, perform the following: ① Online configuration (coding) to write the vehicle VIN and configuration code; ② Crash sensor calibration (use a spirit level to ensure the vehicle is absolutely level); ③ Seat belt pretensioner configuration. Finally, clear the fault codes and perform a system self-check (cycle the ignition 3 times to verify no faults remain).
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM-i Intermittent SRS ECU Reset Fault

✓
The instrument cluster intermittently displayed 'Check SRS System' with intermittent fault code B16BF. Technicians found the G101 ground point below the left A-pillar had a loose mounting bolt and an oxidised contact surface. After servicing the ground point, the fault remained. Further measurements revealed a poor connection in the power supply harness between the instrument panel distribution box and the SRS ECU near the steering column; voltage fluctuated between 8–12V when the harness was moved. Repairing the harness connector eliminated the fault. This case shows that unstable power supply is a common cause of B16BF.
BYD DTC AI Analysis

BYD Yuan EV SRS ECU internal memory damaged

✓
Customer reported the airbag warning light staying on. Scan tool showed code B16BF, which could not be cleared. Power supply, ground, and CAN bus all normal. A software refresh attempt displayed 'ECU not responding' on the scan tool. Removed the SRS ECU (located beneath the gear selector) and found electrolytic capacitor leakage on the circuit board that had corroded the solder joints of a nearby EEPROM chip. Installed a new SRS ECU, then performed online configuration and impact sensor calibration (using VDS2000, selecting 'Yuan EV' model menu). Fault resolved.
BYD DTC AI Analysis

CAN bus interference in BYD Qin Pro DM caused B16BF

✓
After a minor collision, the front bumper was replaced. Fault code B16BF then appeared. We found the front impact sensor wiring harness had been pinched during installation, causing an intermittent short between the CAN-H line and the body. Although the sensor itself was not faulty, the surge voltage from the short circuit triggered a protective lockout of the SRS ECU communication interface. We repaired the wiring harness insulation, cleared the code, and the system returned to normal. This case shows the need to check wiring harness integrity after collision repairs.
BYD DTC AI Analysis

BYD Song MAX software version defect

✓
Early model Song MAX vehicles (2019 MY) built before the batch recall exhibited B16BF faults. A BYD technical bulletin confirmed this as an ECU software bug: during cold starts below -10°C, a timing error in the ECU self-diagnostic routine caused false fault reports. The fix: flash the ECU to the latest software using VDS2000 (version suffix must be greater than V2.3.1), then perform sensor recalibration. Three months of monitoring after the flash showed no further faults.
BYD DTC AI Analysis

SRS fault caused by aftermarket modification to BYD Han EV

✓
During installation of a 360-degree surround view camera system, the installer mistakenly connected the reversing light power wire to the SRS ECU IGN power supply line, causing ECU supply voltage fluctuations. This triggered DTC B16BF and multiple sensor communication faults. Inspection found the modified wiring had damaged the original harness insulation, and the SRS ECU fuse holder was burned. Repaired the original harness, removed the unauthorised wiring, and replaced the fuse holder and SRS ECU (overvoltage had damaged the internal voltage regulator module). Fault resolved.
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.