AU
B16C1-00

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

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 U indicates an internal fault or functional failure in the airbag system electronic control unit. This is a medium-severity safety issue because airbags or seat belt pretensioners may not work correctly in a collision. Common causes include an internal SRS ECU circuit board failure or unstable power supply from poor wiring, voltage fluctuation, or ground corrosion. 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 U
  • 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 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 CAN-H or CAN-L line short circuits, open circuits, 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 causing safety algorithm verification failure.
  • 5External physical damage or water ingress: vehicle wading, ECU mounting compartment seal failure allowing moisture ingress, 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 is present or appears with 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 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 1 Ω). Check if fuses F1/15 (10A) and F1/16 (10A) are blown.
  • 3
    Communication line inspection: Reconnect the battery, turn the ignition ON, and use an oscilloscope to measure the static voltage and dynamic waveform of CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V). Check the terminal resistance (approx. 60Ω) and verify there are no short or open circuits in the wiring.
  • 4
    Visual and physical inspection: Remove the SRS ECU from the centre tunnel or centre console (usually below the gear selector or behind the glovebox). Check the housing for cracks, signs of water ingress, burnt odor, or pin corrosion. Check the mounting bracket for deformation causing stress on the ECU.
  • 5
    Software flash attempt (if supported): For some programmable ECUs, attempt to 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; flash success rate is low).
  • 6
    Replace SRS ECU: If the above checks show no abnormalities and the fault code persists, replace the airbag control unit with 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
    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 conduct 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

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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 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.