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B16C1-00

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

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.

The B16C1-00 fault code on the Qin Plus indicates an internal fault in the airbag control unit (SRS ECU). This is a medium-severity safety issue because airbags or seat belt pretensioners may not work correctly in a crash. Common causes include internal ECU circuit failure or unstable power/ground supply. The recommended fix is to visit an authorised dealer for diagnosis and ECU repair or replacement. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal circuit board fault: Aging, cold solder joints, or burnout of the control module's internal CPU, capacitors, resistors, or integrated circuit components causes the self-test program to fail.
  • 2Abnormal power supply: excessive battery voltage fluctuation (above 16V or below 9V), poor contact in 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 CAN-H or CAN-L line short circuit, open circuit, or abnormal resistance, preventing the ECU from completing the network communication self-check.
  • 4ECU software/data corruption: Internal EEPROM data loss, calibration data corruption, or flash memory failure resulting in safety algorithm verification failure.
  • 5External physical damage or water ingress: vehicle wading, ECU mounting compartment seal failure causing moisture intrusion, or collision causing ECU housing deformation and internal component damage.
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 accompanied by related communication fault codes. Record the fault code freeze-frame data and 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 (must equal battery voltage), check the ignition switch power (IGN) continuity, measure the ground wire resistance (must be less than 1Ω), and 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 voltages and dynamic waveforms of CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V). Check the terminal resistance (approximately 60Ω) to rule out short or open circuits in the wiring.
  • 4
    Visual and physical inspection: Remove the SRS ECU from the center tunnel or center console (usually located beneath 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 reflash 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 typically a hardware fault; reflash 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.
  • 8
    Functional verification: Perform a system self-check cycle test, simulate a crash signal (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

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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 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.