AU
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 8

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.

The B16C8-00 fault code on the Atto 8 indicates an internal fault or critical failure in the airbag control unit, which may disable airbag deployment and affect high-voltage safety functions. Severity is medium, but it directly impacts crash protection. Common causes include an internal SRS ECU hardware failure or unstable power supply from a fuse, relay, or wiring issue. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1SRS ECU internal hardware fault: Damaged CPU, EEPROM memory chip, or power management IC inside the control unit, typically due to 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: A 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 wiring between the SRS ECU and the Vehicle Control Unit (VBU) or BCM, causing the ECU to go offline.
  • 5Water ingress or moisture corrosion: On Qin series models, the SRS ECU mounts beneath the center console or near the floor. After driving through water, water easily enters and corrodes the circuit board or oxidizes the connectors.
What To Do
  • 1
    Safety preparation: Turn off the ignition switch, 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. Check for accompanying fault codes (such as a crash sensor communication fault). Confirm the fault is current and not a historical intermittent fault.
  • 3
    Power and ground check: Measure the voltage between the SRS ECU connector B+ terminal (constant power) and ground; the voltage must be 12 ± 0.5 V. With the ignition switch ON, the IGN terminal voltage must be 12 V. Measure the resistance between the ground terminal and the battery negative terminal; the resistance must be less than 1 Ω. If the resistance exceeds 1 Ω, clean or tighten the ground point.
  • 4
    Communication line check: Measure the diagnostic CAN or powertrain CAN voltages at CAN-H (approx. 2.6-2.8V to ground) and CAN-L (approx. 2.2-2.4V to ground), and measure the bus termination resistance (approx. 60Ω) to rule out wiring short or open circuits.
  • 5
    Component visual inspection: Remove and inspect the SRS ECU (located under the centre console or in front of the gear selector). Inspect the housing for cracks, water marks, or mould. Check the connector pins for oxidation or push-out. If necessary, measure the voltage of the backup capacitor inside the ECU.
  • 6
    Control Unit Replacement: If all wiring measurements are normal, the ECU has an internal fault. Replace the SRS ECU assembly (verify the part number; e.g., Qin EV300 uses the BYD-3636100-XX series). Before installation, verify 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 Write', 'Crash Sensor Zero-Point Calibration', and 'System Self-Test'. Some models require entering the security configuration code (SCN coding).
  • 8
    Function verification: Reconnect the battery, turn on the ignition switch, and confirm the instrument cluster SRS warning lamp 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 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 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.