AU
B16C3

DTC B16C3 indicates a functional fault in the airbag system electronic control unit (SRS_ECU) — Qin Plus

Safety System

DTC B16C3 indicates a functional fault in the airbag system electronic control unit (SRS_ECU).

The SRS_ECU is the core controller of the safety system.

It monitors crash sensor signals in real time, processes crash algorithms, controls the deployment timing of the airbags and seat belt pretensioners, and manages the communication network of the entire passive safety system.

This DTC usually indicates an internal processor or memory fault in the ECU, or a loss of communication between the ECU and the vehicle CAN network.

An intermittent open circuit in the ECU power supply or ground circuit can also trigger this fault.

This fault causes the airbag system to enter fail-safe mode.

The airbags may fail to deploy in a collision, creating a serious safety risk.

The B16C3 fault code on the Qin Plus indicates a functional fault in the airbag system control unit (SRS ECU). Severity is medium because the system may enter fail-safe mode, and airbags or seat belt pretensioners may not work in a crash. Common causes include unstable ECU power or ground supply, blown fuses, or CAN bus communication faults. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from 3 recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Abnormal SRS ECU power supply circuit: Includes a blown constant power (B+) circuit fuse, poor relay contact, or unstable IGN supply voltage causing the ECU operating voltage to drop below 9V or exceed 16V.
  • 2CAN bus communication fault: Short circuit, open circuit, or abnormal terminating resistance in the communication line between the SRS_ECU and the vehicle network (powertrain CAN or dedicated safety CAN), preventing the ECU from communicating normally with the instrument cluster, VCU, and other modules.
  • 3ECU internal hardware damage: Control unit internal memory data corruption, processor clock fault, or collision detection circuit self-test failure, usually resulting from electromagnetic interference, overvoltage, or component aging.
  • 4Sensor circuit short: A short to ground or power in the front impact sensor, side impact sensor, or clock spring circuit triggers the ECU protective shutdown function.
  • 5Software calibration error: Corrupted ECU internal calibration data, incomplete flashing, or failure to perform online configuration (coding) after part replacement causes abnormal system recognition.
What To Do
  • 1
    Safety Preparation and Initial Diagnosis: Disconnect the high-voltage system (for new energy vehicles) and wait 5 minutes to allow capacitors to discharge. Use the BYD VDS diagnostic tool to read all fault codes. Confirm if B16C3 is an active fault and check for accompanying communication fault codes (such as the U01XX series). Record freeze frame data and note vehicle speed, voltage, and other data when the fault occurred.
  • 2
    Power and ground check: Check if the front compartment distribution box SRS fuses (such as F1/15 and F2/13) are blown. Disconnect the battery negative terminal, wait 90 seconds, and unplug the SRS ECU connector. Measure the voltage between pin 1 (constant power +B) and ground (should equal battery voltage). Measure the resistance between the ground pin and body ground (should be less than 1Ω). Inspect the connector for oxidation or backed-out pins.
  • 3
    Communication Line Inspection: Reconnect the battery and turn the ignition switch to the ON position (do not start the vehicle). Use an oscilloscope to measure the CAN-H (pin 6) and CAN-L (pin 14) waveforms at the SRS ECU connector. The standard waveform is a square-wave signal with CAN-H at 2.5-3.5V and CAN-L at 1.5-2.5V. If the voltage is abnormal (e.g., both are close to 0V or 12V), check the wiring harness for shorts to ground or open circuits.
  • 4
    Sensor circuit inspection: Check the wiring harness connectors for the front impact sensor (located on the longitudinal beam) and the side airbag sensor. Measure the sensor resistance to confirm it is within the standard range (usually 2-3 kΩ). Check the steering wheel clock spring (spiral cable) continuity. Verify the driver-side airbag circuit resistance is normal (2-3 Ω) to rule out ECU misjudgment caused by a sensor circuit fault.
  • 5
    ECU replacement and calibration: If all wiring measurements are normal, update the SRS ECU software (if BYD has released a relevant upgrade package). If the fault persists, replace the SRS ECU. After replacement, use VDS to perform 'Online Coding' and 'Calibration'. Enter the correct vehicle VIN and safety configuration code. Finally, clear the fault codes, perform a system self-check (the indicator lamp should turn off), and perform a simulated crash test (using dedicated equipment) to verify system functionality.
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX: Faulty evaporator temperature sensor caused air conditioning failure

✓
Poor A/C cooling, vent temperature not low enough, intermittent compressor operation. VDS scan found DTC B2A2F09 (evaporator temperature sensor fault). Data stream showed evaporator temperature fixed at –40°C (clearly abnormal). Further inspection revealed backed-out pins in the evaporator temperature sensor connector causing poor contact. Re-secured the sensor connector pins and cleared the fault code. Data stream returned to normal and A/C cooling function was restored.
Original source ↗
BYD DTC AI Analysis

BYD Qin DM: A/C compressor not starting

✓
After turning on the A/C, no cold air blew from the vents, the compressor did not start, and the recirculation/fresh air switching was inoperative. The owner initially ran an OBD scan and found multiple communication fault codes in the climate control system. Inspection at the dealership confirmed an abnormal power supply to the HVAC control module. The A/C compressor fuse in the engine bay fuse box had blown. Replacing the fuse did not fix the fault. Further investigation revealed an internal short circuit in the A/C pressure switch, triggering system protection. After replacing the pressure switch, the compressor worked normally and the fault was fully resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro automatic A/C temperature control fault

✓
The fault symptoms were a significant discrepancy between the set temperature and actual air outlet temperature, a noticeable temperature difference between the left and right air vents, and abnormal fan speed adjustment in AUTO mode. A dealership technician used a scan tool to retrieve fault codes related to the temperature blend door actuator. Checking the live data from each temperature sensor, the technician found the cabin temperature sensor reading deviated from the actual ambient temperature by about 15°C. The technician diagnosed a failed cabin temperature sensor (located inside the dashboard). The repair involved replacing the cabin temperature sensor and recalibrating the blend door actuator using the scan tool. After the repair, temperature control accuracy returned to normal.
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.