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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) — Qin Plus

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
5
Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal hardware fault: Damage to the control unit's internal CPU, EEPROM memory chip, or power management IC, 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: 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 terminating resistance in the Power CAN or Comfort CAN lines between the SRS ECU, Vehicle Control Unit (VBU), and BCM, causing the ECU to go offline.
  • 5Water ingress or moisture corrosion: The SRS ECU in Qin series models mounts beneath the center console or near the floor. Water exposure easily causes water ingress, leading to circuit board corrosion or connector oxidation.
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 and 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, 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 should be 12±0.5V. With the ignition switch ON, the IGN terminal voltage should be 12V. Measure the resistance between the ground terminal and the battery negative terminal; the resistance should be less than 1Ω. If the resistance is greater than 1Ω, clean or tighten the ground point.
  • 4
    Communication line check: Measure the voltage of CAN-H (approx. 2.6-2.8V to ground) and CAN-L (approx. 2.2-2.4V to ground) on the diagnostic CAN or powertrain CAN, and the bus termination resistance (approx. 60Ω), to rule out wiring shorts or open circuits.
  • 5
    Component visual inspection: Remove and inspect the SRS ECU (located under the center console or in front of the gear selector). Inspect the housing for cracks, water marks, or mold. Check the connector pins for oxidation or backed-out pins. If necessary, measure the voltage of the internal ECU backup capacitor.
  • 6
    Control unit replacement: If all circuit measurements are normal, the ECU has an internal fault. Replace the SRS ECU assembly (verify the part number; for example, the 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
    Functional verification: Reconnect the battery, turn on the ignition, 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 codes and perform a road test to confirm no intermittent faults exist.
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 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.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.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.
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.