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B16C8-00

DTC B16C8-00 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU, BYD internal code SR8) — Atto 3

Safety System

DTC B16C8-00 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU, BYD internal code SR8).

As the core of the passive safety system, this ECU monitors front and side impact sensor signals, vehicle deceleration, and seat belt status in real time.

Upon detecting a collision, it controls airbag ignition, seat belt pretensioner activation, and high-voltage system power-off protection.

This DTC triggers when the ECU self-check detects an internal processor fault, memory checksum error, power supply monitoring abnormality, or safety monitoring circuit failure, forcing the entire airbag system into fail-safe mode.

In this state, the airbag system will not deploy regardless of collision severity.

The vehicle may also restrict high-voltage power-on or enter limp mode.

This severe fault compromises driving safety.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1SRS ECU internal hardware fault: Damaged CPU, EEPROM memory chip, or power management IC within the control unit, typically resulting from component aging or electrostatic breakdown.
  • 2Power supply system fault: Poor connection in the SRS ECU constant power (B+) or ignition power (IGN) circuit, blown fuse, or poor relay contact, causing ECU operating voltage to drop below 9V or exceed 16V.
  • 3Ground circuit fault: Loose, oxidized, or corroded ECU ground point (usually G101 or G102) increases circuit resistance and affects the signal reference voltage.
  • 4CAN bus communication fault: Short circuit, open circuit, or abnormal terminal resistance in the Power CAN or Comfort CAN lines between the SRS ECU and the Vehicle Control Unit (VBU) or BCM, causing the ECU to go offline.
  • 5Water ingress or moisture corrosion: Qin series models house the SRS ECU under the centre console or near the floor. Water exposure easily leads to water ingress, causing circuit board corrosion or connector oxidation.
What To Do
  • 1
    Safety preparation: Turn off the ignition, disconnect the low-voltage battery negative terminal, and wait at least 3 minutes (to fully discharge the SRS capacitor) to prevent accidental airbag deployment.
  • 2
    Fault confirmation: Connect the BYD VDS2000 or ED400 diagnostic tool, read the B16C8-00 current status and freeze frame data, and check for associated fault codes (such as a crash sensor communication fault). Confirm the fault is current, not historical or intermittent.
  • 3
    Power supply and ground check: Measure the voltage between the SRS ECU connector B+ terminal (constant power) and ground. The voltage must be 12±0.5V. Turn the ignition switch ON. The IGN terminal voltage must be 12V. Measure the resistance between the ground terminal and the battery negative terminal. The resistance must be less than 1Ω. If the resistance exceeds 1Ω, clean or tighten the ground point.
  • 4
    Communication line check: Measure the CAN-H (about 2.6-2.8 V to ground) and CAN-L (about 2.2-2.4 V to ground) voltages on the diagnostic CAN or powertrain CAN. Measure the bus terminating resistance (about 60 Ω) to rule out a short or open circuit in the wiring.
  • 5
    Component visual inspection: Remove and inspect the SRS ECU (located beneath the center console or in front of the gear selector). Inspect the housing for cracks, water stains, or mold. Check the connector pins for oxidation or backed-out pins. If necessary, measure the ECU internal backup capacitor voltage.
  • 6
    Control unit replacement: If all wiring measurements are normal, determine the fault is internal to the ECU and replace the SRS ECU assembly (verify the part number; e.g., Qin EV300 uses the BYD-3636100-XX series). Before installation, confirm the vehicle configuration code matches the VIN.
  • 7
    System configuration and calibration: After installing the new ECU, use the diagnostic tool to perform 'SRS system configuration writing', 'crash sensor zero-point calibration', and 'system self-check'. Some models require entering the safety configuration code (SCN coding).
  • 8
    Function check: Reconnect the battery, turn on the ignition, and confirm the SRS warning lamp on the instrument cluster turns off after the self-check. Use the diagnostic tool to perform the 'Crash Simulation Test' (does not deploy the airbag, only checks circuit resistance). Clear the fault code and perform a road test to confirm there are no intermittent faults.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV300 SRS ECU internal processor fault

✓
The airbag warning light suddenly illuminated on the dashboard of a 2017 Qin EV300 while driving. Scanned with VDS, retrieved DTC B16C8-00 (SR8_ECU fault), and the code could not be cleared. ECU power supply (12.4V) and ground (0.3Ω) were normal; CAN bus waveform showed no abnormalities. Disassembled the SRS ECU and found no visible burn marks on the internal circuit board, so determined an internal CPU or memory logic fault. Replaced with a same-model SRS ECU (P/N 3636100-XXXX), performed system configuration and sensor calibration. Fault light turned off and system self-test passed.
Original source ↗
BYD DTC AI Analysis

Qin 80 SRS control unit corroded after water ingress

✓
After driving through floodwater, the dashboard displayed "Check Airbag System". The scanner retrieved DTC B16C8-00 and multiple collision sensor communication faults. Inspection found wet floor carpet. Removed the SRS ECU (located under the centre console) and discovered the housing seal had perished, with electrolytic corrosion on the internal circuit board and green copper oxide between the pins causing a short circuit. Replaced the ECU, cleaned the oxides from the wiring harness connectors, and dried the interior. Fault resolved. Recommend checking for blocked drain holes.
BYD DTC AI Analysis

Qin EV450 ECU locked due to incomplete configuration after accident repair

✓
During front-end collision repairs, the front impact sensors and SRS ECU were replaced, but DTC B16C8-00 remained after switching on the ignition. Inspection found the new ECU had not been configured, causing security authentication to fail. Using VDS, the technician executed the Airbag ECU Replacement Procedure, entered the SCN (Security Configuration Code) matching the VIN, and recalibrated the impact sensors (zero-point calibration). The DTC cleared successfully, and the airbag system resumed its normal self-test.
BYD DTC AI Analysis

SRS warning light comes on intermittently on rough roads

✓
The owner reported the SRS warning light occasionally flashes when driving over speed humps. The scan tool retrieved intermittent B16C8-00 and communication timeout faults. Static inspection showed no abnormalities. Dynamic monitoring of the CAN bus revealed momentary open circuits during bumps. Final inspection found the SRS ECU wiring harness connector lock tab had fractured, causing the connector to work loose while driving. Secured the harness and replaced the connector housing, applied conductive paste to the terminals, and completed a continuous 20 km road test with no recurrence of the fault.
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.