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 — Seal U

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 Seal U indicates an internal fault in the Airbag Control Unit or abnormal communication with the vehicle network. Severity is medium, but it can disable airbags and seat belt pretensioners, so the vehicle should not be ignored. Common causes include low or unstable power supply, poor ECU grounding, or an internal SRS ECU failure. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Abnormal SRS ECU power supply or ground circuit: Includes 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: Damaged ECU internal microprocessor, memory (EEPROM), or crash sensor interface circuit. Common causes include vehicle water ingress, moisture at the ECU mounting location, or component aging (Qin series ECUs mount in the lower center console, exposing them to air-conditioning condensation).
  • 3CAN communication bus fault: A short circuit, open circuit, or abnormal terminating resistance in the power CAN (CAN-H/CAN-L) circuit between the SRS ECU and the gateway (GW) prevents 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. Interrupted programming, improper battery disconnection, or electromagnetic interference may cause this.
  • 5Crash data locked: After a minor collision, the SRS ECU records the crash 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 12V battery negative terminal for 5 minutes to perform an ECU hard reset, then restore 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 connectors B05-1 (constant +B) and B05-2 (IGN power); the standard value is 11-14V. Check the ground resistance at B05-3 and B05-4; the value must be <1Ω. Inspect the lower center console wiring harness for signs of 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 of SRS ECU connector pins B05-5 (CAN-H) and B05-6 (CAN-L) to ground and power. Check for a short to ground or short to power.
  • 4
    ECU unit inspection: Remove the centre console panel and the SRS ECU (located behind the gear selector mechanism). Inspect the housing for cracks, water marks or corrosion. If the unit shows signs of water ingress, simultaneously check the air conditioning drain pipe for blockages to prevent repeat damage.
  • 5
    Software update and calibration: If the wiring is normal, attempt to update the SRS ECU software (SPS programming) or rewrite the configuration data. On some Qin EV models, execute the 'SRS System Configuration' function via VDS to write the correct vehicle VIN and airbag configuration parameters.
  • 6
    Component replacement and verification: If the above 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 (using the diagnostic tool to execute an 'active test') 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 Seal U Fault Codes
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.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.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.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.