AU
B16C6-00

DTC B16C6-00 indicates the Airbag Control Unit (SRS ECU) detected an internal self-check fault or abnormal communication with the vehicle network — Atto 8

Safety System

DTC B16C6-00 indicates the Airbag Control Unit (SRS ECU) detected an internal self-check fault or abnormal communication with the vehicle network.

The SRS ECU is the core controller of the passive safety system, monitoring crash sensors, seat occupancy detection, seat belt pretensioners, and individual airbag modules.

When this DTC triggers, the ECU may enter fail-safe mode, degrading or completely disabling the entire airbag system.

As a result, the front dual airbags, side airbags, and pretensioning seat belts may fail to deploy during a collision.

This is a hard fault and will not clear automatically after a vehicle restart.

Troubleshooting requires professional diagnostic equipment.

The B16C6-00 fault code on the Atto 8 indicates a medium-severity fault in the airbag control unit, such as an internal self-check failure or abnormal network communication. Possible causes include an unstable SRS ECU power or ground supply, a blown airbag fuse, low battery voltage, or an internal ECU hardware fault. The airbag system may be disabled, so 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 — Atto 8
  • 1Abnormal SRS ECU power supply or ground circuit: including blown FB-10 (10A) airbag system fuse, low battery voltage (<9V), or poor contact at ECU ground points G104/G105, causing unstable ECU operating voltage or reset.
  • 2SRS ECU internal hardware fault: Damage to the ECU internal microprocessor, memory (EEPROM), or crash sensor interface circuit. This commonly results from vehicle water ingress, moisture at the ECU mounting location, or component aging (on Qin series models, the ECU mounts in the lower center console, exposing it to air-conditioning condensation).
  • 3CAN communication bus fault: Short circuit, open circuit, or abnormal terminating resistor in the Power CAN (CAN-H/CAN-L) lines between the SRS ECU and the gateway (GW), preventing the ECU from communicating normally with the instrument cluster, VTOG, and other modules.
  • 4Software or calibration data corrupted: ECU internal flash memory data checksum failed. Possible causes include interrupted programming, improper battery disconnection, or electromagnetic interference.
  • 5Crash data locked: After a minor collision, the SRS ECU records the collision event and locks (Crash Data Locked). Replace or unlock the ECU.
What To Do
  • 1
    Preparation and Diagnosis: Access the SRS system using the ED-400 or VDS2000 diagnostic tool. Read the complete fault code list and record the freeze frame data. Confirm if B16C6-00 is a current fault (Active). Disconnect the battery negative terminal for 5 minutes to perform an ECU hard reset. Reconnect power and check if the fault code returns.
  • 2
    Power and ground check: Check if the FB-10 fuse (10A) in the engine compartment fuse box is blown. Measure the voltage to ground at SRS ECU connector terminals B05-1 (constant +B) and B05-2 (IGN power). Standard value: 11-14V. Measure the ground resistance at B05-3 and B05-4. Standard value: <1Ω. Thoroughly inspect the lower center console wiring harness for wear or water ingress.
  • 3
    Communication line inspection: Turn the ignition switch OFF. Measure the resistance between diagnostic connector pins 6 (CAN-H) and 14 (CAN-L). Standard value: 60 ± 6 Ω. Measure the insulation to ground and power supply at SRS ECU connector pins B05-5 (CAN-H) and B05-6 (CAN-L) to check for a short to ground or short to power.
  • 4
    ECU main unit inspection: Remove the center console panel, then remove the SRS ECU (located behind the gear selector mechanism). Check the housing for cracks, water stains, or corrosion. If water ingress is evident, also check the air conditioning drain hose for blockages to prevent repeat damage.
  • 5
    Software update and calibration: If wiring is normal, update the SRS ECU software (SPS programming) or rewrite the configuration data. For some Qin EV models, use VDS to execute the 'SRS System Configuration' function and write the correct vehicle VIN and airbag configuration parameters.
  • 6
    Component replacement and verification: If the previous steps fail, replace the SRS ECU with the same part number (e.g., 5A-5820100 series). After installing the new ECU, perform 'online coding' and 'seat occupancy recognition calibration'. Clear the fault codes, then perform a simulated crash test (execute the 'activation test' using the diagnostic tool) to confirm normal system operation.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 instrument panel SRS warning light stays on, with DTC B16C6-00

✓
A 2017 Qin EV300 with 80,000 km on the clock had the airbag warning light on the instrument panel stay on continuously. Used VDS2000 to retrieve codes B16C6-00 (SRS ECU fault) and U0151 (lost communication with SRS ECU). Found green corrosion on SRS ECU connector B05, located beneath the centre console. Disassembly revealed the air conditioning evaporator drain hose had detached, allowing condensate to seep into the ECU mounting cavity. Replaced the SRS ECU (part number 5A-5820100), corrected the drain hose routing, and fitted a waterproof gasket at the ECU bracket. After fixing the fault, performed seat occupancy sensor calibration and the system self-check passed.
BYD DTC AI Analysis

Qin 80 SRS system won't come online after accident repair

✓
A 2017 BYD Qin 80 sustained a minor front impact. After a repair shop replaced the front bumper and radar sensors, DTC B16C6-00 appeared and could not be cleared. Diagnosis found the SRS ECU had stored a crash event (Crash Data) and entered a locked state. Since BYD SRS ECUs are single-use (unless officially unlocked), attempts to clear the code failed. Final solution: Replaced the SRS ECU with a new one, used the ED-400 to perform the 'New Module Assembly' procedure, and programmed the VIN and configuration data (front dual airbags plus side airbags). The airbag warning light went out after the self-check.
BYD DTC AI Analysis

Qin EV450 intermittent SRS warning light accompanied by multi-system communication fault.

✓
A 2018 Qin EV450 intermittently displayed an SRS warning light accompanied by heavy steering (EPS fault). The diagnostic tool retrieved DTC B16C6-00 and multiple U-series communication fault codes. CAN-H resistance to ground at the diagnostic connector measured 2.3 Ω (abnormal). Tracing section by section pinpointed the fault to the CAN bus junction under the left A-pillar, where the SRS ECU CAN wire had chafed against a metal bracket, wearing through the insulation and shorting to ground. After repairing the harness and rerouting the wiring, all communication faults and DTC B16C6-00 disappeared, and the SRS system returned to normal operation.
BYD DTC AI Analysis

Qin 100: SRS system reports ECU fault after battery replacement

✓
A 2017 Qin 100 displayed 'SRS System Fault' on the dash after a general repair shop replaced the battery. Retrieved DTC B16C6-00. The technician had not disconnected the negative battery terminal during the replacement, causing power fluctuations during removal and installation that triggered an SRS ECU internal data validation error. Used VDS to perform 'SRS ECU Programming' and reflashed the SRS ECU with the latest 5A-5820100 series software (version upgraded from V1.2 to V1.4). After programming, executed 'System Configuration' and 'Clear Collision Records'. The fault code cleared and the airbag system passed self-diagnosis.
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.