AU
B16A3

DTC B16A3 indicates an internal fault in the airbag electronic control unit (SRS ECU, also known as the ACU - Airbag Control Module) — Qin Plus

Safety System

DTC B16A3 indicates an internal fault in the airbag electronic control unit (SRS ECU, also known as the ACU - Airbag Control Module).

This fault points to an abnormality within the ECU processor, memory (EEPROM), power supply monitoring circuit, or safety sensor monitoring circuit, rather than an issue with external airbags, sensors, or wiring harnesses.

The ECU internal self-diagnostic program triggers this DTC when it detects key circuit parameters exceeding thresholds (e.g., internal voltage reference deviation, memory checksum failure, or watchdog reset).

This fault may prevent the airbag system from deploying normally during a collision or create a risk of unintended deployment.

It constitutes a core fault in the passive safety system and requires immediate resolution.

The B16A3 fault code on the Qin Plus indicates an internal fault within the airbag control unit (SRS ECU), affecting its processor, memory, or power supply circuits. This medium severity issue may prevent airbag deployment or cause unintended deployment. Common causes include damaged internal memory or power supply monitoring circuit faults. Visit an authorised dealer immediately for repair. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal memory damaged or data verification failed (crash algorithm parameters and configuration codes stored in EEPROM missing or damaged).
  • 2ECU internal power supply monitoring circuit fault (abnormal internal voltage regulator output causes the ECU to incorrectly determine its power supply status)
  • 3External power supply system fault (IG1 power supply voltage fluctuation or excessive ground point contact resistance, causing an ECU internal low-voltage reset)
  • 4A collision or severe shock damages the internal ECU acceleration sensor or locks the crash record (Crash Locked status), triggering an internal fault even without airbag deployment.
  • 5ECU software/firmware version defect or flashing failure (interrupted upgrade process causes configuration data loss on some models)
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the capacitors and prevent accidental airbag deployment; read and record all fault codes and freeze frame data.
  • 2
    Basic inspection: Inspect the SRS ECU exterior for physical damage or water ingress; verify fuse F1/15 (IG1 power supply) is intact; check ECU connectors G36/G37 for oxidation or backed-out pins.
  • 3
    Power supply and ground verification: Measure voltage from G36-1 (IG1) to ground (should be 11-14V); measure resistance from G36-35 (GND) to body ground (should be <1Ω); measure resistance between the ECU housing and body ground (should be <1Ω to ensure good shield grounding).
  • 4
    Communication bus check: Measure CAN-H (G36-25) and CAN-L (G36-26) voltage to ground (expected: 2.5-3.5V and 1.5-2.5V respectively); measure terminal resistance (approx. 60Ω); rule out false ECU reporting caused by CAN communication interference.
  • 5
    Isolation test: Disconnect all airbag component and crash sensor connectors. Leave only the ECU power supply connected. Restore power and read the fault codes. If B16A3 remains, this confirms an internal ECU fault. If the code clears, reconnect the components one by one to locate the short circuit.
  • 6
    ECU replacement and configuration: Replace the SRS ECU with a new unit. Use VDS or a dedicated diagnostic tool to perform: ① VIN writing ② Vehicle configuration code (Option Code) matching ③ Longitudinal/lateral acceleration sensor zero-point calibration ④ System self-check (no fault codes present and airbag warning lamp off)
Real-World Cases
BYD DTC AI Analysis

BYD Qin SRS-ECU internal memory fault

✓
Symptoms: Airbag warning light constantly illuminated on the instrument cluster. DTC B16A3-00 stored. No collision history recorded. Diagnostic procedure: Measured ECU supply voltage at 12.4V – normal. Ground resistance 0.3Ω – normal. CAN bus communication showed no faults. Disconnected all airbag module connectors; the fault code remained. ECU showed no external damage, but internal EEPROM data verification failed (diagnostic tool showed ECU status code 0x01 error). Solution: Replaced the airbag control unit (ACU). Used VDS to write the VIN and perform sensor calibration. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin SRS multiple faults (B16A3+B1693+U0146)

✓
Symptoms: Intermittent airbag warning light while driving. DTCs retrieved with a scan tool: B16A3-00 (SRS ECU fault), B1693-00 (poor earth connection), U0146-00 (lost communication with gateway). Diagnostic process: Found the main body earth point G104 bolt loose. Tightened it — B1693 and U0146 cleared, but B16A3 remained. Further inspection showed insulating paint on the contact surface between the ECU housing mounting bracket and body, causing poor ECU housing earth (resistance >5Ω). Sanded the surface; fault code persisted. Determined the ECU internal power monitoring circuit had failed due to long-term poor earthing. Solution: Replaced the SRS ECU and ensured good housing earth. Fault completely resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song MAX SRS ECU Configuration Lost Fault

✓
Symptoms: Airbag warning light on after servicing. DTCs B16A3-00 and B16A1-00 stored (ECU fault). Diagnosis: The vehicle had just received a gateway module software upgrade. Checked ECU power, ground, and communication – all normal. Scan tool showed internal ECU configuration data error (Checksum Error). Communication between the gateway and SRS ECU was interrupted during the upgrade, corrupting the ECU configuration parameters. Resolution: Reflashed SRS ECU firmware and restored configuration codes. Cleared DTCs after successful flash. System self-test passed. No hardware replacement required.
Original source ↗
BYD DTC AI Analysis

BYD Yuan EV ECU lockout fault after collision

✓
Symptoms: Vehicle had a low-speed collision (front bumper damaged, airbags did not deploy). Airbag warning light on. Read DTC B16A3-00. Diagnosis: Inspected front and rear impact sensors – no damage found. Wiring harness resistance normal. ECU power supply normal. Connected scan tool to view ECU internal status; 'Crash Locked' flag set. Internal accelerometer recorded the impact, triggering lockout protection mode. Fix: Per BYD workshop manual, ECU must be replaced once crash record locks. Fitted new ECU and performed system calibration. Fault cleared.
Original source ↗
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.