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B16BA

DTC B16BA indicates an internal fault or system-level communication fault in the airbag control unit (SRS ECU) — Qin Plus

Safety System

DTC B16BA indicates an internal fault or system-level communication fault in the airbag control unit (SRS ECU).

As the core controller of the passive safety system, the SRS ECU monitors crash sensor signals, evaluates crash severity, triggers airbag and seat belt pretensioner deployment, and continuously performs system self-diagnostics.

This DTC typically indicates an internal ECU microprocessor fault, an EEPROM data checksum failure, a power supply monitoring circuit abnormality, or a CAN bus communication interruption.

The ECU sets this DTC and enters degraded mode when it detects an internal circuit fault, a supply voltage outside the normal 9-16V range, or a loss of communication with the vehicle network exceeding the specified time (typically >500ms).

In this state, the vehicle may completely lose crash protection functions (airbags will not deploy) or risk unintended deployment.

This constitutes a high-risk safety fault.

The B16BA fault code on the Qin Plus indicates an internal fault or communication problem in the airbag control unit. Severity is medium, but it can affect airbag and seat belt pretensioner operation, so it should be treated seriously. Common causes include a faulty SRS ECU or unstable power/ground supply. The recommended fix is to 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 — Qin Plus
  • 1SRS ECU internal hardware fault: internal capacitor aging and leakage, MCU crash, memory data corruption (EEPROM checksum error). Common in 2018–2020 production batch controllers.
  • 2Power supply system fault: battery voltage below 9V or above 16V, excessive contact resistance in the IGN+ power circuit (>1Ω), or loose or oxidized ECU ground wire, causing ECU reset or unstable operation.
  • 3CAN network communication fault: Short or open circuit in the Powertrain CAN (PT-CAN) or Body CAN (Body-CAN) wiring, or terminal resistance deviation (normal 60Ω±5Ω), preventing the ECU from communicating with the vehicle control unit.
  • 4External component short circuit/overload: A short to power or short to ground in the front collision sensor, side airbag module, or seat occupancy detection sensor circuit triggers the ECU internal protection circuit and reports a hardware fault.
  • 5Software/calibration data error: Interrupted OTA update, diagnostic tool programming failure, or failure to perform Online Coding after an accident, causing lost internal ECU parameters or a version mismatch.
What To Do
  • 1
    Safety preparation and initial inspection: Disconnect the 12V battery negative terminal and wait 3 minutes to discharge residual voltage. Inspect the SRS ECU exterior for physical damage, water ingress, or burn marks. Inspect the SRS-related fuses in the dashboard fuse box (typically 10A-15A) and the cabin wiring harness connectors (near the OBD port/GW connector).
  • 2
    Power supply and ground circuit test: Use a multimeter to measure the voltage to ground at ECU connector Pin30 (constant power +B) and Pin15 (IGN power). The standard value is battery voltage ±0.5V. Measure the resistance to ground at ground Pin31; the value must be <1Ω. Check the connector terminals for backed-out pins, enlarged sockets, or green oxidation.
  • 3
    CAN bus communication diagnosis: Connect the VDS2000/Launch diagnostic tool, read the vehicle network topology, and check the SRS ECU communication status. Measure the CAN-H (Pin 7) and CAN-L (Pin 8) voltage to ground (standard: approx. 2.5V) and the resistance between them (standard: approx. 60Ω, measure with power off) to rule out a short or open circuit in the wiring.
  • 4
    Peripheral circuit continuity check: Use a dedicated probe or adapter to measure the circuit resistance of each crash sensor (front/side/center) and airbag module at the ECU connector (standard value: 2.0-3.0 Ω). Check for a short to ground or short to power (resistance <1 Ω or >10 kΩ is abnormal).
  • 5
    Software flashing and configuration: If the wiring is normal, perform 'SRS system online calibration' or 'ECU software upgrade' (requires a BYD DiLink authorized account). Rewrite the calibration data and write the configuration code (Coding). Clear the fault code, then perform an ignition cycle test.
  • 6
    ECU replacement and matching: If the above steps fail, replace the SRS ECU with the same part number (distinguish between high-spec and low-spec versions), execute the 'ECU Replacement' online matching procedure, synchronize the vehicle VIN and configuration parameters, and finally perform a system self-check (no fault codes) and an airbag simulated deployment test (using the dedicated tool).
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM SRS light stays on after accident repair

✓
A 2021 Tang DM showed 'Check SRS System' on the instrument cluster after a minor rear-end collision. The technician retrieved DTC B16BA. Inspection found accident damage to the left front engine bay wiring harness. During the repair, the IGN power connector to the SRS ECU was not fully seated, causing a contact resistance of 3.2 Ω. The technician re-crimped the power terminal, measured contact resistance below 0.1 Ω, cleared the DTC, and the system returned to normal.
BYD DTC AI Analysis

12V battery power loss caused ECU reset fault on Yuan EV

✓
The owner of a 2019 Yuan EV reported the vehicle failed to start after being parked for one week. After a jump-start, the SRS warning light stayed on constantly and DTC B16BA was logged. Diagnosis found the battery voltage had dropped to only 8.5V. A voltage spike during the jump-start exceeded 18V, causing the SRS ECU internal memory data checksum to fail. Replaced the battery with an AGM unit, used a diagnostic tool to execute the 'SRS System Data Recovery' function, then reset the ECU. Fault resolved.
BYD DTC AI Analysis

ECU internal short circuit after water ingress - Song MAX

✓
A Song MAX drove through floodwater during heavy rain, causing the SRS system to fail and log code B16BA. Disassembly revealed the SRS ECU beneath the centre console had an aged seal; water ingress had corroded the PCB, and capacitor C102 had leaked. Resolution: Replaced the SRS ECU assembly, replaced the water-affected harness connectors, performed online programming and matching, and checked the insulation of all airbag modules.
BYD DTC AI Analysis

Short in Qin Pro side airbag circuit triggers ECU protection

✓
2020 Qin Pro: SRS warning light came on after seat cover replacement. Fault codes B16BA and B1620 stored (driver side airbag fault). Inspection found the seat rails had pinched and damaged the side airbag wiring harness during seat removal and installation, causing two wires to short to ground. The SRS ECU detected the circuit abnormality, entered protection mode and reported an ECU hardware fault. Repaired the wiring harness insulation, replaced the damaged side airbag module and cleared the fault codes.
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.