AU
B17A200

This DTC indicates that the airbag control unit (SRS ECU) has detected a collision event meeting the deployment threshold, permanently written the crash data to the ECU internal non-volatile memory (NVRAM), and activated the crash lock protection mechanism — Atto 3

Safety System

This DTC indicates that the airbag control unit (SRS ECU) has detected a collision event meeting the deployment threshold, permanently written the crash data to the ECU internal non-volatile memory (NVRAM), and activated the crash lock protection mechanism.

In this state, the SRS system enters safe mode, disables further airbag deployment to prevent secondary injury, and illuminates the warning lamp continuously.

A genuine collision event (deployed or recorded without deployment) can trigger this lock.

Crash sensor faults, wiring harness short/open circuits, ECU algorithm miscalculations, or power supply system anomalies can also generate a false record.

Once locked, standard DTC clearing cannot erase the code.

Reset the data using dedicated diagnostic equipment, or replace the ECU.

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Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1The vehicle experienced an actual collision (regardless of airbag deployment), and the SRS ECU recorded longitudinal/lateral acceleration sensor data and locked the system.
  • 2Internal short circuit, open circuit, or signal drift in the front collision sensor, side collision sensor, or center sensor causes the ECU to receive an abnormal acceleration signal.
  • 3SRS ECU internal memory chip damage, software bugs, or power supply fluctuations (such as voltage spikes when jump-starting a dead battery) causing erroneous writing to the data area.
  • 4Handling the airbag wiring harness during repairs without disconnecting the battery, or water ingress or oxidation in the yellow (airbag-specific) connector causing abnormal resistance and triggering a false collision detection.
  • 5Locked SRS ECU not replaced during accident repairs (on some BYD models, the ECU is a single-use component; replace it after recording a collision).
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000/3000 or ED400) to access the SRS system. Read the complete fault codes, freeze frame data, and crash record. Verify the trigger time, triggered sensor location, and collision severity value (Delta-V).
  • 2
    Check the vehicle repair history against the freeze frame time. Visually inspect the front and rear longitudinal beams, crash beams, B-pillars, and sills for signs of sheet metal repair to confirm a genuine collision or a false alarm.
  • 3
    Disconnect the 12V battery negative terminal for 3 minutes. Inspect all yellow SRS wiring harness connectors (especially the floor harness and sensor connectors) for water ingress or corrosion. Measure the crash sensor resistance (normal: 2.0–3.0 kΩ; abnormal: short circuit <1 kΩ or open circuit >10 kΩ).
  • 4
    If confirmed as a false alarm with no hardware damage: Use the diagnostic tool to perform the 'Crash Data Clear' function. Input the authorized BYD manufacturer password. If the ECU does not support clearing or clearing fails, replace the SRS ECU with a brand-new unit (the part number must match the vehicle configuration).
  • 5
    If a genuine collision occurred: replace all deployed airbag modules, seat belt pretensioners, and crash sensors, and install a new SRS ECU (do not reuse a locked ECU).
  • 6
    After replacing the hardware, perform ECU coding, sensor calibration, and a system self-check. Road test the vehicle to confirm DTC B17A200 does not return and the airbag warning lamp is off.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro DM: SRS light stays on after accident repair

✓
2019 Qin Pro DM, minor front-end collision (bumper only, airbags did not deploy). After an external workshop replaced the bumper, the airbag warning light stayed on. VDS showed B17A200 Crash Record Locked; freeze frame indicated collision intensity of -1.2g (minor collision threshold). The shop had ignored the SRS system. Since the airbags never deployed, cleared the crash data using the manufacturer-authorized password, completed sensor calibration, and resolved the fault—avoiding replacement of the expensive ECU.
BYD DTC AI Analysis

Water ingress caused sensor short circuit and false locking.

✓
2018 BYD Qin Pro petrol. After driving in heavy rain, the instrument cluster showed an airbag fault. The scan tool retrieved DTCs B17A200 and B17A111 (left front impact sensor fault). Inspection found water ingress and oxidation in the left front rail impact sensor connector, with resistance at only 0.3kΩ (severe short). This caused the ECU to misdetect a frontal collision and lock the collision record. Replaced the left front impact sensor, cleaned the wiring harness connector, and cleared the collision record using the scan tool. System returned to normal.
BYD DTC AI Analysis

Collision record locked after battery replacement

✓
A 2019 Qin PRO DM displayed an airbag warning light at startup after technicians replaced the battery at a dealership. Scanning revealed DTC B17A200 with no other codes. The technician failed to disconnect the SRS power supply before removing the old battery. Voltage fluctuations during reconnection caused the ECU to log a false trigger. No collision damage was present. Technicians performed an ECU Reset via VDS and cleared the codes to resolve the issue—a typical software fault from power interference.
BYD DTC AI Analysis

SRS ECU internal damage; replacement required

✓
2018 Qin Pro DM, no accident history. SRS warning light suddenly lit. Scan tool showed DTC B17A200 and would not clear. Freeze frame data showed corruption (timestamp 1970, impact values abnormal). All sensors and wiring harnesses tested normal. Diagnosed as ECU internal storage chip failure. Replaced SRS ECU with new unit (Part No. SC-3638100). Completed online programming, coding and sensor calibration. Fault resolved. Old ECU analysis: Physical damage to internal Flash memory caused erroneous crash flag writing.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
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.