AU
B16C1-00

DTC B16C1-00 indicates an internal fault or functional failure of the airbag system electronic control unit (SRS_ECU) — Atto 3

Safety System

DTC B16C1-00 indicates an internal fault or functional failure of the airbag system electronic control unit (SRS_ECU).

This fault represents a core self-check abnormality of the airbag control module.

It typically indicates a hardware-level fault in the ECU internal processor, memory, power management circuit, or safety monitoring circuit.

This fault causes the airbag system to enter a degraded mode or complete failure state.

During a collision, the system may fail to deploy the airbags, making this a critical fault affecting vehicle passive safety.

Upon fault detection, the SRS system typically illuminates the instrument cluster airbag warning light (solid) and logs a non-clearable hard fault code.

Some models may also trigger the seat belt pretensioner disable logic.

4
Cases Logged
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Causes
Likely Causes — Atto 3
  • 1SRS ECU internal circuit board fault: Aging, cold solder joints, or burned-out internal control module components (CPU, capacitors, resistors, or integrated circuits) cause the self-check procedure to fail.
  • 2Abnormal power supply: excessive battery voltage fluctuation (above 16V or below 9V), poor contact in the ECU constant power or ignition power circuits, or ground point corrosion causing unstable ECU operating voltage.
  • 3CAN communication bus fault: Abnormal communication between the SRS ECU and the vehicle network, including short circuit, open circuit, or abnormal resistance in the CAN-H or CAN-L lines, preventing the ECU from completing the network communication self-check.
  • 4ECU software/data corruption: Internal EEPROM data loss, calibration data corruption, or flash memory fault causing safety algorithm verification failure.
  • 5External physical damage or water ingress: vehicle wading, ECU mounting compartment seal failure causing moisture intrusion, or collision damage deforming the ECU housing and damaging internal components.
What To Do
  • 1
    Diagnostic confirmation: Use the BYD VDS2000 or VDS3100 diagnostic tool to read all fault codes. Confirm only B16C1-00 is present, or appears with related communication fault codes. Record the fault code freeze frame data. Check the instrument panel SRS warning light status.
  • 2
    Power supply and ground check: Disconnect the battery negative terminal. Measure the voltage between the SRS ECU connector constant power (B+) terminal and ground (should be battery voltage). Check the continuity of the ignition switch power (IGN). Measure the ground wire resistance (should be less than 1Ω). Check if fuses F1/15 (10A) and F1/16 (10A) are blown.
  • 3
    Communication line inspection: Reconnect the battery and turn the ignition switch to ON. Use an oscilloscope to measure the static voltage and dynamic waveforms of CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V). Check the terminal resistance (approx. 60Ω) to rule out a short or open circuit in the wiring.
  • 4
    Visual and physical inspection: Remove the SRS ECU from the centre tunnel or centre console (usually located below the gear selector or behind the glovebox). Check the housing for cracks, signs of water ingress, burnt odors, or pin corrosion. Check the mounting bracket for deformation causing stress on the ECU.
  • 5
    Software flash attempt (if supported): For some programmable ECUs, flash the SRS system software or rewrite the configuration data, then check if the fault code clears. (Note: B16C1-00 is usually a hardware fault; flash success rate is low.)
  • 6
    Replace SRS ECU: If the above checks are normal and the fault code persists, replace the airbag control unit with one of the same part number. (Note: Match the specific vehicle configuration code. Qin series ECUs from different model years are not interchangeable.)
  • 7
    Programming and matching: Use the diagnostic tool to perform 'Airbag System Configuration', 'VIN Writing', 'Crash Sensor Calibration', and 'System Self-check'. Clear all fault codes and confirm the SRS warning light turns off normally.
  • 8
    Function verification: Perform a system self-check cycle test, simulate a crash signal test (using dedicated equipment), verify the seat belt pretensioner and airbag circuit resistance values are normal, and perform a road test to confirm the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 SRS warning light came on suddenly while driving

✓
A 2017 Qin EV300 with 82,000 km came in because the airbag warning light suddenly came on and stayed on while driving. We scanned with a VDS2000 and retrieved DTC B16C1-00 (SRS ECU fault). The vehicle had no collision history. The ECU supply voltage was normal (12.4 V), and the CAN bus waveform was also normal, but the DTC returned immediately after clearing. Disassembling the ECU revealed obvious burn marks on the internal PCB, indicating the power management chip had failed. We replaced the SRS ECU with a new unit (Part No.: BYD-3638100-X00), performed online programming and sensor calibration, and the fault was resolved.
BYD DTC AI Analysis

B16C1-00 occurs intermittently after accident repair

✓
2018 BYD Qin EV450. After front collision repairs, the SRS warning light illuminated intermittently. The scan tool displayed current DTC B16C1-00 with history DTC U0140 (lost communication with SRS ECU). Inspection revealed the accident had slightly deformed the ECU mounting bracket, causing the ECU housing to contact the metal bracket and create stress, along with a poor connection on pin 12 (constant power) of the ECU connector. After repairing the harness connector and replacing the deformed bracket, DTC B16C1-00 still appeared occasionally. The accident impact and voltage fluctuations had damaged the ECU internal circuitry. Replacing the ECU resolved the fault completely.
BYD DTC AI Analysis

SRS system failure on water-wading vehicle

✓
2017 BYD Qin 100. After wading through water up to seat height in heavy rain, the SRS warning light stayed on after towing. Read fault codes: B16C1-00 and multiple airbag igniter short circuit faults. Inspection found the SRS ECU seal beneath the centre tunnel had failed, with severe internal circuit board corrosion and several broken, oxidised copper traces. Cleaned the wiring harness connectors and confirmed normal insulation readings. Replaced the ECU and sealing gasket, and dried the ECU mounting compartment. Performed full system configuration after replacement. Cleared the fault codes and confirmed all airbag circuit resistances returned to normal (2.0–2.8 Ω).
BYD DTC AI Analysis

Replaced the ECU after software flash failure.

✓
A 2017 BYD Qin 80 set DTC B16C1-00 after an SRS software update at a dealership. The vehicle had no collision history. Diagnosis showed the ECU lost power while reflashing, corrupting the internal data. Reflash attempts triggered a 'security authentication failed' warning. Power, ground, and communication circuit checks were all normal. The ECU internal flash memory was faulty. Replaced the ECU with an identical unit. Using the dedicated diagnostic tool, ran the 'airbag control unit replacement' procedure: wrote the VIN and configuration parameters, then performed 'lateral/longitudinal acceleration sensor calibration'. Fault cleared.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.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.
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.