AU
B16BF-00

B16BF-00 indicates the airbag control unit (SRS ECU) detected an internal fault or critical function failure — Atto 8

Safety System

B16BF-00 indicates the airbag control unit (SRS ECU) detected an internal fault or critical function failure.

This DTC represents a core Safety System fault, indicating the SRS ECU cannot execute crash detection algorithms, airbag deployment logic, or communication with other safety modules (such as seat belt pretensioners, crash sensors, and the vehicle CAN network).

Specific causes include an ECU internal processor or memory fault, a power management module anomaly, a damaged deployment circuit driver chip, a Safing Sensor self-test failure, or an EEPROM data checksum error.

This fault forces the entire airbag system into fail-safe mode.

During a collision, the system may fail to deploy the driver airbag, front passenger airbag, side airbags, and seat belt pretensioners, posing a severe safety hazard.

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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Abnormal SRS ECU power supply/ground: Includes poor connection in the battery constant power (+B) circuit, blown fuse in the ignition switch power (IG) circuit, or ground terminal oxidation/corrosion causing unstable voltage, triggering ECU reset or logic errors.
  • 2CAN bus communication fault: Short circuit, open circuit, or terminal resistor drift (standard 60Ω) on the power CAN or dedicated safety CAN between the SRS ECU and the vehicle gateway or instrument cluster isolates the ECU from the network.
  • 3ECU internal hardware damage: capacitor aging and leakage, cracked PCB solder joints (common on early Qin series models), main control chip (MCU) program crash, or Flash data corruption.
  • 4Crash sensor circuit fault: Front or side crash sensor wiring shorts to ground or opens, and resistance falls outside the normal 1.5-3.0kΩ range, causing the ECU to detect a sensor system fault and set its own fault code.
  • 5Environmental corrosion: Vehicle wading (water level above the floor line) or high-humidity environments degrade the ECU housing seal, allowing moisture to corrode the internal circuit board. The SRS ECU mounting position below the center tunnel is particularly prone to accumulating condensation.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 5 minutes (10 minutes for some models) to fully discharge the SRS ECU internal backup capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap.
  • 2
    Initial inspection: Check the instrument cluster AIRBAG warning light status. Use a VDS2000/3000 or Launch X431 diagnostic tool to read all DTCs. Check for accompanying B16C0 (passenger airbag fault), U-series communication faults, or specific sensor faults. Inspect the SRS ECU housing and mounting bracket for collision deformation or water ingress.
  • 3
    Power and ground measurement: Connect the battery and turn the ignition switch to ON. Measure the voltage between SRS ECU connector terminal 1 (+B, constant power) and ground; it must be 12V. Measure the voltage between terminal 2 (IG, ignition power) and ground; it must be 12V with the ignition ON. Measure the resistance between terminal 3 (GND, ground) and ground; it must be <1Ω. If abnormal, check engine compartment fuse box F1/15 (SRS fuse 10A) and floor wiring harness ground point G202.
  • 4
    Communication line diagnosis: Measure the voltage at diagnostic connector terminals 6 (CAN-H) and 14 (CAN-L). Normal values are approximately 2.6V and 2.4V respectively. Measure the resistance between the CAN lines at the SRS ECU. It should be 60Ω±5Ω (if the ECU has a built-in terminating resistor). Check the wiring harness for interference and wear against the center tunnel.
  • 5
    Sensor circuit check: Disconnect the battery, unplug the SRS ECU connector, and measure the crash sensor circuit resistance (front sensor normal value approx. 2.0kΩ, side sensor approx. 3.0kΩ). Check for a short to ground (<1Ω) or an open circuit (>10kΩ).
  • 6
    Replacement verification: If wiring is normal but the fault code persists, perform a substitution test using an SRS ECU with the same part number (Note: Do not dismantle or repair the ECU). BYD Qin series SRS ECU part numbers are typically 6A-3636100 or EJ-3636100.
  • 7
    Programming and configuration: After replacing the ECU, use the diagnostic tool to perform 'SRS System Configuration': write the vehicle VIN, configure the airbag type (single/dual-stage ignition), perform crash sensor zero calibration (Zero Calibration), and run the system self-check (System Check).
  • 8
    Verification and handover: Clear all DTCs. Cycle the ignition switch 3 times and confirm the warning lamp turns off after the self-check. Perform a road test. Use the diagnostic tool to monitor the SRS system status data stream (Status Byte). It should display 'Normal'.
Real-World Cases
BYD DTC AI Analysis

Internal capacitor electrolyte leak in the SRS ECU causes intermittent fault on BYD Qin 100

✓
Symptoms: The airbag warning light on a 2017 Qin 100 illuminates intermittently while driving and turns off after restarting. DTC B16BF-00 occurs intermittently. Diagnosis: Slight electrolyte leakage marks found on the SRS ECU housing (located under the centre console at the front of the central tunnel). Disassembled the ECU and found that the internal main filter capacitor (2200μF/16V) had leaked, corroding the PCB copper traces. Resolution: Replaced the SRS ECU assembly (part number 6A-3636100). Programmed the VIN and calibrated the crash sensors on the new ECU due to data loss from the old unit. The fault has not recurred since the repair.
BYD DTC AI Analysis

Qin EV300: SRS communication fault after wading, falsely reporting ECU fault

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After wading through water about 30 cm deep, the dashboard displayed “Check SRS System”. Retrieved DTCs B16BF-00 and U0151-00 (Lost communication with ACU). Diagnosis: Measured SRS ECU power supply normal, but CAN-H shorted to earth (0 Ω resistance). Disassembly revealed the floor harness insulation chafed through at the front passenger seat rail mounting clip. Water residue from the wading caused the CAN wire to short to earth, putting the SRS ECU into protective fault mode. Solution: Repaired the damaged harness, wrapped with waterproof tape, and rerouted the harness to avoid seat interference. Cleaned the ECU connector and reinstalled the ECU. Cleared the fault codes; system returned to normal. No ECU replacement needed.
BYD DTC AI Analysis

Qin EV450 SRS ECU data locked after collision

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Symptoms: Vehicle involved in a front low-speed collision (airbags did not deploy). After collision repair and front bumper replacement, the airbag warning light remained on, with DTCs B16BF-00 (SRS ECU fault) and B1650-00 (front impact sensor fault). Diagnosis: Used scan tool to read ECU internal data. Found ‘Crash Record’ lock flag set to 1 and abnormal ignition loop capacitor voltage. According to BYD safety strategy, once the ECU records a collision event (even if below ignition threshold), it locks and becomes unusable. Resolution: Replaced the SRS ECU with a new unit. Also replaced both front impact sensors (since they may have developed internal micro-cracks). Performed complete system configuration and self-test.
BYD DTC AI Analysis

Qin 80: Aftermarket audio installation caused poor SRS ground

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Symptoms: After the owner installed an aftermarket infotainment system, the airbag warning light flashed over rough roads. The scan tool showed DTC B16BF-00. Diagnosis: Inspection found the installer had accidentally loosened the SRS ECU ground wire (G202 ground point) while tapping into the wiring. The new equipment shared this ground point, causing a voltage drop. Voltage measurements showed the ECU supply dropped below 9 V over bumps, triggering an ECU low‑voltage reset fault. Solution: Restored the factory ground wiring and grounded the aftermarket equipment separately to the chassis rail. Re‑tightened the G202 ground point bolt to 9 N·m. Fault resolved.
Other Atto 8 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.