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B16BC-00

DTC B16BC-00 indicates the airbag control unit (SRS ECU) internal self-check detected a severe fault, causing the system to enter fail-safe mode — Qin Plus

Safety System

DTC B16BC-00 indicates the airbag control unit (SRS ECU) internal self-check detected a severe fault, causing the system to enter fail-safe mode.

This fault involves hardware failures or data checksum errors in core ECU components, including the main control processor (MCU), internal acceleration sensor (G-sensor), power management module, or memory (EEPROM/Flash).

When this fault occurs, the SRS ECU may fail to accurately assess collision severity, preventing passive safety devices such as airbags and seat belt pretensioners from deploying correctly during a crash, or creating a risk of unintended deployment.

The system illuminates the instrument cluster airbag warning light and disables the entire airbag system.

The vehicle remains drivable but loses crash protection functions, constituting a severe fault that affects driving safety.

The B16BC-00 fault code on the Qin Plus indicates a medium-severity internal fault in the airbag control unit, causing the SRS system to enter fail-safe mode and disable airbag protection. Possible causes include a faulty internal power regulation circuit or corrupted EEPROM/Flash data after low or unstable voltage. The vehicle should be inspected by an authorised dealer, who may reprogram or replace the SRS ECU. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal power regulation circuit fault (e.g., damaged 12V to 5V/3.3V voltage regulator chip) causes abnormal MCU power supply, triggering an internal watchdog reset.
  • 2Internal memory data corruption (checksum failure of crash threshold, VIN, and configuration parameters stored in EEPROM); commonly occurs after disconnecting vehicle power for repairs or experiencing unstable voltage.
  • 3Built-in acceleration sensor (MEMS chip) signal drift or failure prevents the ECU from obtaining accurate vehicle deceleration data.
  • 4Cold solder joints on the ECU main board, or aging and cracking of surface-mount components (capacitors, resistors), especially in high-temperature environments or after vehicle wading.
  • 5Software logic error or program runaway (Watchdog timeout) preventing the ECU from completing the self-check cycle.
What To Do
  • 1
    Use the BYD ED400/ED600 diagnostic tool to read all fault codes. Confirm whether B16BC-00 is a current (Active) or historical (History) fault, and record freeze frame data (crash sensor values, supply voltage, temperature, etc.).
  • 2
    Check the SRS ECU power supply circuit: measure the connector terminal for constant power (B+, should be 12V battery voltage), ignition switch power (IG, should be 12V in the ON position), and the ground wire (GND, resistance should be less than 1Ω). Check fuse F1/17 (SRS ECU power supply, usually 10A/15A).
  • 3
    Check the CAN communication lines: Measure the voltage to ground at diagnostic connector pins 6 (CAN-H) and 14 (CAN-L) (CAN-H approximately 2.6-2.8V, CAN-L approximately 2.2-2.4V) and the terminal resistance (approximately 60Ω) to rule out false codes caused by network communication failures.
  • 4
    Perform SRS system calibration: Access Special Functions on the diagnostic tool and execute 'Acceleration Sensor Zero Point Calibration' and 'Longitudinal/Lateral Sensor Learning'. Check if the fault code clears. If the calibration fails or the fault code reappears immediately, this indicates a hardware fault.
  • 5
    Software update attempt: If wiring is normal, use the diagnostic tool to update the SRS ECU software (version number must match vehicle configuration; Qin series typically requires SVN_3.XX or higher). Back up coding data before updating.
  • 6
    Replace SRS ECU: If the above steps fail, replace the airbag control module (verify the part number against the vehicle configuration: Qin EV300 uses EQ-5820100; Qin 100 uses MQB-5820100). Before replacement, disconnect the 12V battery negative terminal and wait at least 3 minutes to prevent static electricity from deploying the airbag.
  • 7
    New module configuration and matching: After installing the new ECU, perform 'ECU coding' (write the VIN and vehicle configuration code), 'sensor ID registration' (register the IDs of all crash sensors and airbag modules), and a 'system self-check'. Finally, perform a simulated crash test (use the diagnostic tool to trigger the signal, and verify the warning light turns off and the system status is normal).
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV300: Damaged internal power supply chip in SRS ECU causing intermittent fault

✓
A 2017 BYD Qin EV300 with 80,000 km had an intermittent airbag warning light, with DTC B16BC-00. The fault mostly appeared after the vehicle warmed up. Power supply to the ECU measured normal. Removed the SRS ECU (located beneath the centre console) and found cold solder joints on the U2 voltage regulator chip (LM2937) on the internal PCB, causing the 3.3V output to fluctuate. Re-soldered the chip and reinforced the joints to clear the fault, avoiding replacement of the expensive ECU assembly.
BYD DTC AI Analysis

Qin 100 lost memory data after battery discharge

✓
The vehicle sat for an extended period, draining the battery completely (voltage below 8V). After a jump start, the instrument cluster displayed an SRS fault. Retrieved DTC B16BC-00 (current). The scan tool showed 'configuration data checksum error'. The power loss corrupted the crash algorithm parameters in the EEPROM. I used the BYD dedicated diagnostic tool to run the 'data recovery' function, downloading the OEM configuration data for this VIN from the cloud and writing it to the ECU. The fault code cleared and the system returned to normal.
BYD DTC AI Analysis

Qin EV450 ECU internal corrosion after wading

✓
The vehicle drove through water that exceeded the door sill height, after which the SRS warning light stayed on constantly. The system logged DTC B16BC-00 along with multiple crash sensor communication faults. Inspection found traces of water ingress at the SRS ECU mounting location beneath the floor. Disassembly of the ECU housing revealed electrolytic corrosion on the internal circuit board and oxidised pins on the main control chip. Cleaning the PCB and replacing the corroded surface-mount capacitors did not resolve the issue. Replaced the ECU with a new unit, dried the wiring harness connectors, and checked for blocked drain holes, completely resolving the problem.
BYD DTC AI Analysis

Qin 80 modifications cause CAN bus interference and false alarms.

✓
The owner fitted an aftermarket dashcam (powered via the OBD port). While driving, the SRS warning light illuminated randomly. The diagnostic scanner retrieved code B16BC-00 (historical). Measurements revealed abnormal pulse interference on the CAN-H line (amplitude reaching 4.5V). After removing the aftermarket OBD power adapter, the fault did not recur. The external device either occupied the SRS ECU's CAN communication bandwidth or introduced electromagnetic interference, causing the ECU to misinterpret a communication timeout as an internal fault. Advised the owner to use fuse box constant power or cigarette lighter power instead.
BYD DTC AI Analysis

Fixed the Qin EV300 software version defect by upgrading.

✓
A 2018 BYD Qin EV300 with no accidents or modifications. SRS warning light came on suddenly, code B16BC-00. Wiring inspection found no issues. Battery disconnect reset didn’t work. Checked BYD technical bulletin TSB-SRS-2019-03 — confirmed this production batch has an ECU software bug that falsely reports internal faults when starting at temperatures between -5°C and 5°C. Upgraded software from V2.1 to V2.4, cleared the code. After one week of road testing, no recurrence.
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.