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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) — Seal 6 EV

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 Seal 6 EV indicates an internal failure in the airbag control unit (SRS ECU). This is a medium-severity safety fault because airbags or seat belt pretensioners may not work correctly in a crash. Common causes include internal ECU circuit damage or unstable power/ground supply. The first recommended fix is to 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 — Seal 6 EV
  • 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-check program 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 a short circuit, open circuit, or abnormal resistance in the CAN-H or CAN-L line, 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 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 or related communication fault codes are present. Record the fault code freeze frame data. Check the instrument panel SRS warning light status.
  • 2
    Power supply and ground check: Disconnect the negative battery 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 terminating resistance (approximately 60Ω) to rule out short or open circuits in the wiring.
  • 4
    Visual and physical inspection: Remove the SRS ECU from the centre tunnel or centre console (usually located beneath the gear selector or behind the glovebox). Check the housing for cracks, signs of water ingress, a burnt smell, or pin corrosion. Check the mounting bracket for deformation causing stress on the ECU.
  • 5
    Attempt software flash (if supported): For some programmable ECUs, flash the SRS system software or rewrite the configuration data. Check if the fault code clears. (Note: B16C1-00 is usually a hardware fault; flash success rate is low.)
  • 6
    Replace the 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 verify the SRS warning light turns off.
  • 8
    Functional 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

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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

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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.

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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 Seal 6 EV 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.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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.