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B16BB

DTC B16BB indicates the Airbag Control Unit (SRS_ECU) detected a severe fault during its internal self-test — Qin Plus

Safety System

DTC B16BB indicates the Airbag Control Unit (SRS_ECU) detected a severe fault during its internal self-test.

This typically points to a hardware-level fault in the ECU internal processor, memory, power regulation circuit, or ignition driver circuit.

This means the SRS_ECU cannot execute the crash detection algorithm, cannot drive the airbag ignition circuits, or detected a program memory error during the cyclic redundancy check (CRC).

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

During a collision, all airbags (front airbags, side curtain airbags, knee airbags) and seat belt pretensioners may fail to deploy.

The fault may also affect the active head restraint and crash fuel cut-off functions.

The B16BB fault code on the Qin Plus indicates a severe internal fault in the airbag control unit found during self-test. Severity is medium, but it can put the SRS system in fail-safe mode, so airbags and seat belt pretensioners may not deploy in a crash. Common causes include a burnt ECU power regulator or corrupted EEPROM data. Visit an authorised dealer for diagnosis and ECU repair or replacement. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Burnt SRS ECU internal power supply chip or voltage regulator circuit, often resulting from reversed polarity during jump-starting, alternator voltage regulator failure, or accidental connection to a 24V power supply.
  • 2Corrupted ECU internal EEPROM data, possibly resulting from a high-current surge during a vehicle collision, electromagnetic interference (EMI), or interrupted software flashing.
  • 3ECU seal failure causes internal PCB corrosion, commonly resulting from driving through water, water leaks from blocked sunroof drain tubes, or prolonged parking in high-humidity environments.
  • 4Fault in the ECU internal acceleration sensor (MEMS) or safing sensor signal processing circuit, causing self-test failure.
  • 5Oxidized or backed-out wiring harness connector pins cause poor ECU power or ground connections, repeatedly triggering an internal ECU low-voltage reset (brown-out).
What To Do
  • 1
    Use the VDS3000 diagnostic tool to perform a full SRS system scan. Verify B16BB is a current fault (Active) that will not clear. Check for accompanying communication fault codes (such as codes starting with U).
  • 2
    Check the SRS ECU power supply: Measure the voltage at connector terminal 30 (constant power +B) and terminal 15 (ignition switch power). Voltage must be 9-16 V. Measure the resistance between ground terminal 31 and body ground. Resistance must be less than 0.5 Ω.
  • 3
    Check CAN communication: Measure terminals 6 (CAN-H) and 14 (CAN-L) at the diagnostic connector. Idle voltages should be 2.6V and 2.4V respectively, differential voltage should be 1.8-2.7V, and the waveform should show no distortion.
  • 4
    Visually inspect the ECU housing: check for cracks, water stains, and signs of corrosion. Pay special attention to Yuan/Qin models, where the ECU mounts beneath the center tunnel, for signs of spilled drinks.
  • 5
    Perform ECU removal and inspection: Disconnect the negative battery terminal and wait 3 minutes (capacitor discharge). Remove the ECU and inspect the connector pins for oxidation (green/white). Inspect the interior for signs of water ingress or a burning smell.
  • 6
    If the above checks are normal, replace the SRS ECU with a unit of the same part number (Note: ECU hardware versions differ across BYD models; verify the part number, such as EG-3636000-X).
  • 7
    After installing the new ECU, perform online programming (Coding): write the vehicle VIN and airbag configuration parameters (number of airbags, knee airbag presence, seat occupancy recognition type, etc.) using VDS3000.
  • 8
    Perform system configuration: calibrate the seat occupancy sensor, learn the steering wheel clock spring center position, and perform a crash simulation test (use a dedicated load box instead of the actual airbag to verify the ignition circuit function).
Real-World Cases
BYD DTC AI Analysis

2021 BYD Tang DM SRS ECU internal power supply fault

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Vehicle dash displayed 'Check SRS System'. Scanned DTC B16BB-00. Inspection found an aftermarket audio system had been installed. The installer mistakenly connected the SRS ECU power wire in parallel with the amplifier power wire when tapping constant power, causing voltage to drop below 6V during cranking. This damaged the power management IC inside the SRS ECU. Replaced the SRS ECU and restored the factory wiring harness. Fault resolved. Total repair cost approx. 3200 yuan.
BYD DTC AI Analysis

2019 BYD Yuan EV: SRS fault after water wading

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After driving through water, the airbag warning light stayed on constantly and DTC B16BB was set. Disassembly and inspection found the SRS ECU beneath the center console had a deteriorated housing seal ring, allowing water to seep through the wiring harness boot and corrode the PCB, causing a short circuit. Cleaned and dried the wiring harness connector, installed a new ECU (Part No. EG-3636000-A2), and applied additional waterproof sealant during installation. Fault resolved.
BYD DTC AI Analysis

BYD Song MAX 2019: ECU locked after collision

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The vehicle sustained a minor frontal impact (airbags did not deploy). After repairs, technicians could not clear DTC B16BB. Investigation revealed that when the impact sensor triggered, the ECU logged a collision event flag internally and locked the system. Although the impact did not reach the airbag deployment threshold, the ECU entered an irreversible fault mode. Replaced with a new ECU and recalibrated the seatbelt pyrotechnic pretensioner; the system then returned to normal.
BYD DTC AI Analysis

2020 BYD Qin Pro: Software flash bricked the ECU

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During an SRS system software upgrade at the dealership, the diagnostic tool lost its network connection, causing incomplete ECU programming. The instrument cluster displayed an SRS fault, and the VDS could not communicate. The ECU entered Bootloader mode, but the main program was corrupted, triggering DTC B16BB (hardware fault). Replaced the ECU hardware and reflashed the software using the latest VDS3.0. Fault eliminated.
BYD DTC AI Analysis

BYD Tang II intermittent B16BB fault

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The airbag warning light intermittently illuminates when driving on rough roads, but remains off when stationary. Inspection revealed ECU earth point G202, located beneath the left A-pillar, had resistance fluctuating between 0.5-8Ω due to paint residue from assembly. Sanded the earth point and retightened the bolt to 9N·m. Cleared the fault codes and monitored for one month with no recurrence.
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.