AU
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 — Atto 8

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.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1SRS ECU internal power regulation circuit fault (e.g., damaged 12V to 5V/3.3V voltage regulator chip) causes abnormal MCU power supply and triggers an internal watchdog reset.
  • 2Internal memory data corrupted (verification failed for collision threshold, VIN, or configuration parameters stored in EEPROM). Commonly occurs after disconnecting vehicle power during repairs or due to unstable voltage.
  • 3Built-in acceleration sensor (MEMS chip) signal drift or failure prevents the ECU from obtaining accurate vehicle deceleration data.
  • 4Dry solder joints on the ECU main board or aging and cracking of surface-mounted 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 an Active or History fault and record the freeze frame data (crash sensor values, supply voltage, temperature, etc.).
  • 2
    Check the SRS ECU power supply circuit: measure constant power at the connector terminal (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 circuit: Measure the voltage to ground at diagnostic connector terminals 6 (CAN-H) and 14 (CAN-L) (CAN-H approx. 2.6-2.8 V, CAN-L approx. 2.2-2.4 V) and the terminating resistance (approx. 60 Ω) to rule out false faults caused by network communication failures.
  • 4
    Perform SRS system calibration: access Special Functions on the diagnostic tool, execute 'Acceleration Sensor Zero Point Calibration' and 'Longitudinal/Lateral Sensor Learning', and check if this clears the fault code. If calibration fails or the fault code reappears immediately, this indicates a hardware fault.
  • 5
    Software flash: If wiring is normal, update the SRS ECU software using the diagnostic tool (version number must match vehicle configuration; Qin series typically requires SVN_3.XX or later). Back up coding data before flashing.
  • 6
    Replace SRS ECU: If the above steps fail, replace the airbag control module (verify the part number against the vehicle configuration: EQ-5820100 for Qin EV300, MQB-5820100 for Qin 100). Before replacement, disconnect the 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 a 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 Atto 8 Fault Codes
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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.