AU
B16A1-00

DTC B16A1-00 indicates the Airbag Control Unit (ACU) detected a communication anomaly or internal circuit fault in the Left Side Impact Sensor — Atto 3

Safety System

DTC B16A1-00 indicates the Airbag Control Unit (ACU) detected a communication anomaly or internal circuit fault in the Left Side Impact Sensor.

The SRS_ECU continuously monitors the supply voltage, signal circuit resistance, and LIN/CAN communication frame rate of each impact sensor.

The ECU sets this DTC if it detects an open circuit, short to ground, or short to power in the left sensor wiring, or a sensor data validation error (e.g., capacitance drift, acceleration signal out of range) lasting over 200ms.

Once set, the system enters a degraded mode.

This mode may disable the left side airbag and curtain airbag deployment, or on certain models, restrict the entire airbag system, posing a severe safety hazard.

The B16A1-00 fault code on the Atto 3 indicates a communication error or internal circuit fault in the Left Side Impact Sensor, which can disable the left side and curtain airbags or restrict the entire supplemental restraint system. Common causes include wiring harness connection issues or internal sensor damage. Severity is medium. Typical repair cost data is available from 5 recorded cases. An authorised dealer must diagnose and repair the fault.
5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Internal accelerometer damage or capacitor degradation in the left side impact sensor (located inside the left B-pillar trim panel) causes abnormal signal output.
  • 2Loose connection, water ingress, oxidation, backed-out pins, or poor contact at the wiring harness connector between the SRS ECU and the left-side impact sensor (usually located under the left front seat or at the base of the B-pillar)
  • 3Airbag Control Unit (ACU) internal memory damage, power supply chip fault, or software logic error triggering a false sensor fault.
  • 4Following a left-side collision, loose sensor mounting or internal micro-cracks cause an intermittent open circuit, but the sensor does not meet replacement criteria.
  • 5Low 12V battery voltage or excessive voltage drop in the SRS system power supply circuit prevents the ECU from correctly identifying the sensor during initialization.
What To Do
  • 1
    Connect the VDS2000 or BYD dedicated diagnostic tool. Enter the SRS system and read all DTCs. Confirm whether B16A1-00 is a current fault (Active) or a history fault (History). Record the vehicle speed and sensor voltage values from the freeze frame data.
  • 2
    Disconnect the 12V battery negative terminal, wait 90 seconds for the capacitor to discharge, then remove the left B-pillar lower trim panel. Verify the side impact sensor connector (black plug, 2-pin or 3-pin) locks securely, and inspect the pins for oxidation or backing out. Apply conductive grease if necessary.
  • 3
    Use a multimeter to measure the voltage at the sensor harness connector. With the ignition switch ON, the power supply pin voltage should be 4.8-5.2V and the signal pin voltage should be 2.3-2.7V. Measure the sensor resistance. The normal range is 1.8-3.2kΩ. Replace the sensor if the deviation exceeds ±10%.
  • 4
    Check wiring harness continuity: Test continuity of the wiring harness between the ACU (usually located under the center tunnel) and the left sensor. Verify no open circuits exist and insulation resistance is >1MΩ. Inspect the wiring harness near the seat rail for wear.
  • 5
    If the wiring harness and sensor are normal, update the SRS ECU software (if a newer version is available), or perform the 'Sensor Configuration' and 'Crash Record Clear' functions. If necessary, replace and recode the ACU control unit.
  • 6
    Reconnect all components, restore power, clear the fault codes, and perform a system self-check (wait for the indicator self-check to complete). Perform a road test (including bumpy roads and turns) to confirm the fault code does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Loose left B-pillar sensor connector on Qin EV450 causing intermittent fault

✓
A 2018 Qin EV450 with 32,000 km on the clock occasionally displayed "Check SRS System" on the dashboard; the warning cleared after cycling the ignition. Used VDS to retrieve DTC B16A1-00 (intermittent). Inspected the side impact sensor inside the left B-pillar interior trim and found the connector locking tab had broken, allowing the plug to work loose and causing an intermittent connection when driving over bumps. Replaced the sensor wiring harness connector using a wiring repair kit, re-secured the harness routing, and cleared the fault.
BYD DTC AI Analysis

Qin 100 left impact sensor internal circuit damaged

✓
2017 Qin 100. Airbag warning light stayed on. DTC B16A1-00 (current fault) stored. Sensor power supply measured 5.02V (normal), but sensor signal output voltage was 0.3V (abnormal). Replaced left side impact sensor (part number: K9-5820600). The DTC changed to historical; after clearing it did not reappear. Cause: damaged accelerometer chip inside the sensor.
BYD DTC AI Analysis

Sensors not calibrated after accident repair on Qin EV300

✓
2017 Qin EV300. After a minor left-side collision, an outside shop replaced the left front door and B-pillar outer panel, then the airbag light came on. Diagnostics showed B16A1-00 with B1650-00 (crash data stored). Inspection revealed the shop had reinstalled the left impact sensor but under-torqued the mounting bolts, causing the sensor angle to shift. Re-torqued the bolts to 8 N·m, then used VDS to run impact sensor zero-point calibration and crash data clear. Fault resolved.
BYD DTC AI Analysis

Wiring harness chafing caused a short to earth.

✓
The airbag warning light on a BYD Qin 80 suddenly illuminated while driving. Inspection found the wiring harness protective sleeve near the left front seat rail damaged. The side impact sensor signal wire had chafed against the seat mounting bracket, causing an intermittent short to earth. Repaired the wire by soldering and insulating with heat-shrink tubing, rerouted the harness to avoid the seat slide travel, and replaced the damaged corrugated tubing. Fault resolved.
BYD DTC AI Analysis

SRS ECU software fault causing false alarms

✓
2017 BYD Qin 100. No obvious collision history, but DTC B16A1-00 kept recurring. Replaced the sensor and wiring harness, yet the fault persisted. Checked ACU software version: V1.2. Consulted BYD TSB and found that version has a false-positive defect. Upgraded ACU software to V1.5 and performed sensor configuration matching. The fault has not returned.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.