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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 — Qin Plus

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.

The B16BF fault code on the Qin Plus indicates an internal fault or system-level failure in the airbag control unit. Severity is medium, but it affects a safety-critical system and may prevent airbags or seat belt pretensioners from working correctly. Common causes include a faulty SRS ECU, poor fuse or wiring contact, low battery voltage, or unstable alternator output. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal hardware fault: Damaged main control chip (e.g., Infineon or Renesas series), aging and leaking electrolytic capacitor, or PCB interlayer short circuit. These faults typically cause the ECU housing to heat up or prevent the diagnostic tool from establishing communication.
  • 2Power supply system fault: poor contact at the SRS fuse (usually 10A or 15A) in the instrument panel power distribution box, loose wiring causing voltage to drop below 8V, or discharged battery or unstable alternator output causing ECU reset.
  • 3Ground circuit fault: Loose, oxidized, or paint-covered G101 ground point (located on the dashboard 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 short to ground, short to power, or short together; or terminal 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 runaway, or version bugs. Commonly occurs after interrupted vehicle OTA updates or improper battery disconnection.
What To Do
  • 1
    Initial diagnostic tool check: Access the SRS system using VDS2000/VDS3000. Read the complete fault code list and freeze frame data. Confirm if B16BF is a current (Active) fault. Check for accompanying U-class communication fault codes (such as U0140, U0151). Record the vehicle status at the time of the fault (voltage, temperature, vehicle speed).
  • 2
    Power and ground measurement: Disconnect the negative battery terminal and wait 90 seconds to discharge the SRS capacitor. 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 power +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. Inspect the connector for green corrosion or backed-out pins.
  • 3
    CAN bus check: Connect an oscilloscope or multimeter to measure diagnostic connector pins 6 (CAN-H) and 14 (CAN-L). Static voltage should be approximately 2.6V and 2.4V, respectively. Disconnect the battery and measure the terminal resistance. The resistance should be approximately 60Ω (two 120Ω resistors in parallel). Check if the metal dashboard bracket chafed the wiring harness, causing an intermittent short circuit.
  • 4
    Substitution verification: If the wiring is normal, perform a substitution test using an SRS ECU from a known good vehicle of the same model (connect the plug only; do not fully install the unit). Check if the fault code remains. If the fault disappears, the original ECU hardware is damaged.
  • 5
    Software update attempt: If hardware tests are normal, use VDS2000 to perform an SRS ECU software update and select the latest firmware version (verify the version number applies to the specific model year). Maintain stable battery voltage during the update (a regulated power supply is recommended).
  • 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 airbags and curtain airbags). After installation, perform: ① Online configuration (Coding) to write the vehicle VIN and configuration code; ② Crash sensor calibration (use a spirit level to verify 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 confirm no faults exist).
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM-i Intermittent SRS ECU Reset Fault

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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

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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

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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

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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

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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 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.