AU
B16A0-00

DTC B16A0-00 indicates the airbag control unit (SRS ECU/ACM) detected a severe fault during its internal self-test — Seal U

Safety System

DTC B16A0-00 indicates the airbag control unit (SRS ECU/ACM) detected a severe fault during its internal self-test.

This indicates a hardware-level anomaly in the ECU internal processor, memory, power regulation circuit, or safety monitoring circuit, rather than an external sensor or actuator fault.

The SRS ECU integrates crash discrimination algorithms, firing decision logic, and fault diagnostic functions.

This safety-critical fault means the ECU cannot guarantee reliable airbag and pretensioner deployment during a collision.

The root cause may be internal EEPROM data corruption, CPU calculation errors, abnormal internal voltage monitoring, or watchdog circuit triggering.

This fault typically requires ECU assembly replacement rather than repair.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1ECU internal electronic component failure: aging internal energy storage capacitor, damaged main control chip (MCU), or corrupted memory (EEPROM/Flash) data causing self-test failure.
  • 2Power supply system fault: battery voltage too low (<9V) or too high (>16V), momentary voltage drop at ignition ON, or poor ground wire contact (oxidation at ground points G201/G301), causing abnormal operation of the ECU internal power management module.
  • 3Water ingress or corrosion: Driving through water, leaking air-conditioning condensate, or improper engine bay cleaning corrodes and short-circuits the internal circuit board of the SRS ECU located in the centre tunnel (beneath the gear selector on Qin series models).
  • 4Collision impact damage: Even without airbag deployment, severe acceleration impact during an accident may crack solder joints on the internal ECU circuit board, damage the accelerometer, or deform the housing, causing internal short circuits.
  • 5Unauthorized operation or power loss: Using non-genuine diagnostic equipment, extended battery disconnection (>30 minutes), or improper jump-starting causes ECU internal encrypted data loss or VIN matching errors.
What To Do
  • 1
    Diagnostic confirmation: Use the BYD VDS2000/VDS6000 diagnostic tool to read fault codes. Confirm whether B16A0-00 is the only fault code or if it is accompanied by other communication faults (such as U0146). Record freeze frame data (vehicle speed, voltage, etc. at the time of occurrence).
  • 2
    Basic circuit check: Measure the pin voltages at SRS ECU connectors G09/G10 — constant power (B+) must be 12V ± 0.5V, IGN voltage in the ON position must be 12V, ground resistance <1Ω, and CAN-H (2.6V) / CAN-L (2.4V) terminal resistance approximately 60Ω.
  • 3
    Power supply stability test: Use an oscilloscope to monitor supply voltage during start-up and load changes. Check for voltage drops (<9V) or spikes (>16V). Focus inspection on the F4/9 (10A) fuse and socket contacts.
  • 4
    ECU physical inspection: Remove the centre console armrest box. Inspect the SRS ECU housing for deformation, cracks, water stains, or corrosion. Inspect the connector for oxidation, backed-out pins, or water ingress. If necessary, disassemble the ECU to inspect the circuit board.
  • 5
    Attempt software repair: Perform an 'ECU reset' or 'clear crash history' (if applicable). If the fault code is intermittent and not currently present, attempt to recalibrate the acceleration sensor. However, B16A0-00 usually indicates a hardware fault with a low software repair success rate.
  • 6
    Replace SRS ECU: If the above checks show no abnormalities or the ECU has internal damage, install a new airbag control unit assembly (verify the part number based on the vehicle model, e.g., EQ-5820100 for Qin EV300).
  • 7
    Online matching and programming: Use VDS to execute the 'Airbag ECU Replacement' procedure, perform online anti-theft matching (write the VIN, vehicle configuration code, and airbag configuration parameters), and perform acceleration sensor calibration (G-sensor Calibration).
  • 8
    System verification: Clear all fault codes and perform an ignition cycle test (OFF-ON-START). Confirm the SRS warning lamp turns off after the self-check (turns off after 6 seconds). Perform a simulated crash test (use the diagnostic tool to execute the 'Crash Output Test' to check circuit continuity without deploying the airbag). Finally, perform a road test to verify.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro SRS warning light stays on (no collision history)

✓
Symptoms: After starting the vehicle, the airbag warning light stays on. VDS reads fault code B16A0-00. No other fault codes present. No accident history. Diagnosis: ECU supply voltage 12.4V (normal). Ground connection good. CAN communication normal. No visible damage to the ECU exterior. Power reset and software reset both ineffective. Resolution: Replaced the airbag control unit. Used VDS to perform online matching (wrote VIN and configuration data). After replacement, the warning light turned off and the system self-test passed.
BYD DTC AI Analysis

BYD Song MAX SRS system fault after accident repair

✓
Symptoms: After a minor front-end collision repair, the instrument cluster displayed “Please check SRS system”. VDS retrieved DTCs B16A0-00 (SRS ECU fault) and B1600-00 (driver airbag open circuit). Diagnostic process: Checked the driver airbag resistance (2.3Ω) and wiring harness connections; both normal. Removed and inspected the SRS ECU, finding the housing slightly deformed from accident impact and fine cracks on the internal circuit board. Resolution: Replaced the SRS ECU assembly, along with the deployed driver airbag and seatbelt pretensioners. Cleared the collision history and completed system matching using VDS.
Original source ↗
BYD DTC AI Analysis

Intermittent SRS warning light on BYD Tang DM

✓
Symptoms: SRS warning light intermittently illuminated while driving, occasionally extinguishing after an ignition cycle. Intermittent history fault code B16A0-00 stored. Diagnosis: ECU voltage monitoring found a momentary drop to 9V when switching the ignition. Inspection revealed poor contact at the F4/9 fuse holder in the engine bay fuse box, degraded internal energy storage capacitors (reduced capacity) inside the SRS ECU, and an owner-fitted dashcam wired directly to constant power, causing voltage fluctuations. Resolution: Repaired the poor contact at the F4/9 fuse holder. Rewired the dashcam to ACC power. Replaced the aged SRS ECU and performed programming.
BYD DTC AI Analysis

SRS ECU corrosion fault in water-damaged BYD e5

✓
Symptoms: After flood damage repair, vehicle would not enter READY mode. Instrument cluster displayed "Check SRS system" warning. Retrieved fault codes B16A0-00 and U0146 (loss of SRS communication). Diagnosis: Inspected SRS ECU mounting location under center console and found evidence of water ingress. Removed ECU; found severe internal circuit board corrosion and oxidized G09 connector pins. Power supply circuits measured normal, but ECU would not communicate. Resolution: Replaced SRS ECU. Cleaned oxidation from G09 connector using electronic cleaner and conductive grease. Inspected and replaced damaged floor harness. Performed online programming.
BYD DTC AI Analysis

BYD Yuan EV lost data after replacing the 12V battery.

✓
Symptoms: After a non-AGM standard battery was installed at an independent workshop, the SRS warning light stayed on. Retrieved DTCs B16A0-00 and B1691-00 (factory encryption error). Diagnosis: The battery had been disconnected for over an hour. Checking the ECU data found a VIN mismatch and internal encryption verification failure. The vehicle had no collision history, and the ECU showed no physical damage. Resolution: Used BYD VDS to perform the ‘Airbag ECU Replacement’ procedure — rewrote the VIN and configuration parameters, ran online encryption verification, and cleared the codes. The system returned to normal. Recommendation: Keep the power uninterrupted when replacing the battery.
Original source ↗
Other Seal U 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.