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 — Seal U

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.

The B17A200 fault code on the Seal U indicates the SRS airbag ECU has recorded a crash event and entered crash lock mode, disabling further airbag deployment and keeping the warning light on. Severity is medium, but the system needs prompt attention. Common causes include a real collision or faulty impact sensors/wiring creating a false crash signal. Visit an authorised dealer to reset crash data with dedicated equipment or replace the ECU. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1The vehicle experienced an actual collision (regardless of airbag deployment). The SRS ECU recorded longitudinal/lateral acceleration sensor data and locked the system.
  • 2Internal short circuit, open circuit, or signal drift in the front impact sensor, side impact sensor, or central sensor causes the ECU to receive an abnormal acceleration signal.
  • 3Damage to the SRS ECU internal memory chip, a software bug, or power supply fluctuations (such as voltage spikes when jump-starting a discharged battery) causing erroneous data writes to the data area.
  • 4Working directly on the airbag wiring harness during repairs without disconnecting the battery, or water ingress or oxidation in the yellow connector (airbag-specific) causing abnormal resistance, resulting in a false collision detection.
  • 5Failure to replace the locked SRS ECU during accident repairs (some BYD models use a single-use ECU requiring replacement after recording a collision).
What To Do
  • 1
    Use a dedicated BYD diagnostic tool (VDS2000/3000 or ED400) to access the SRS system. Read the complete fault codes, Freeze Frame data, and Crash Record. Confirm 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 rails, crash beams, B-pillars, and sills for signs of sheet metal repair to confirm whether the event was a genuine collision or a false alarm.
  • 3
    Disconnect the 12V battery negative terminal for 3 minutes. Check all yellow SRS harness connectors (especially the floor harness and sensor connectors) for water ingress or oxidation. Measure the crash sensor resistance (Normal: 2.0–3.0 kΩ; Abnormal: <1 kΩ [short circuit] or >10 kΩ [open circuit]).
  • 4
    If confirmed as a false alarm with no hardware damage: Use the diagnostic tool to perform the 'Crash Data Clear' function and enter the BYD manufacturer-authorized password. If the ECU does not support clearing or clearing fails, replace the SRS ECU with a new unit (part number must match vehicle configuration).
  • 5
    If an actual 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 hardware replacement, perform ECU coding, sensor calibration, and a system self-check. Conduct a road test to confirm DTC B17A200 does not return and the airbag warning light 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 Seal U Fault Codes
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.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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.