AU
B1697-00

DTC B1697-00 indicates the airbag control unit (SRS ECU) internal self-test detected a critical function fault — Seal 6 EV

Safety System

DTC B1697-00 indicates the airbag control unit (SRS ECU) internal self-test detected a critical function fault.

The ECU integrates the acceleration sensor, safing sensor, firing decision logic, and diagnostic communication module.

Potential root causes include: 1) Data verification failure in the ECU internal microprocessor or memory (EEPROM/Flash); 2) Abnormal output from the power management module (12V-5V/3.3V voltage regulator circuit); 3) The crash detection algorithm continuously detecting an internal logic conflict; 4) Communication interface circuit fault with the crash sensors (front door, side airbag, center sensor).

This fault causes the ECU to enter a degraded mode, disabling deployment of the airbags, seat belt pretensioners, and pedestrian protection devices.

In extreme cases, it may cause unintended airbag deployment or failure to deploy during a collision.

This is a safety-critical fault.

The B1697-00 fault code on the Seal 6 EV indicates a critical internal fault in the airbag control unit (SRS ECU), forcing the system into a degraded mode that disables airbags, seat belt pretensioners, and pedestrian protection devices. Severity is medium. Common causes include internal power supply IC failure or thermal fatigue causing voltage drops. This requires visiting an authorised dealer. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Dry solder joint caused by thermal fatigue, or breakdown of the SRS ECU internal power supply IC (such as TLE7263 or similar automotive-grade voltage regulator chip), drops the core supply voltage below 3.0 V (normal: 3.3 V ± 0.1 V).
  • 2Voltage surge (>16V) generated during vehicle battery depletion or jump-starting damages the ECU internal EEPROM data block or causes a checksum error.
  • 3Front/side impact sensor circuit shorted to ground or power (impedance <1Ω or >5Ω); ECU activates protective lockout and records an internal fault.
  • 4A short circuit between diagnostic CAN bus lines (CAN-H and CAN-L) or abnormal terminating resistance (deviating from 60Ω±5%) causes a communication timeout between the ECU and vehicle network, triggering a watchdog reset failure.
  • 5ECU housing seal failure allows moisture ingress and internal PCB oxidation (common after water wading or in high-humidity areas), causing intermittent short circuits in critical signal lines (such as the safing sensor output).
What To Do
  • 1
    Safe power-down: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds (verify SRS backup capacitor voltage is <1V). Do not connect or disconnect airbag-related wiring harnesses while energized.
  • 2
    Visual and connection inspection: Remove the trim panel below the center console and inspect the SRS ECU connector (usually a 24-pin or 32-pin black plug) for looseness, backed-out pins, oxidation, or signs of water ingress. Measure the terminal retention force.
  • 3
    Power supply and ground verification: Reconnect the battery (do not unplug the ECU connector) and measure the ECU connector terminals using a multimeter: constant power (BATT, 30#) must be 12V±0.5V; ignition power (IGN, 15#) must be 12V in the ON position; ground wire (GND) resistance to the body must be <1Ω, and voltage drop must be <0.1V.
  • 4
    Communication bus inspection: Use an oscilloscope or multimeter to measure diagnostic CAN-H (2.5V-3.5V dynamic) and CAN-L (1.5V-2.5V dynamic). The sum of the static voltages must be 5V ± 0.1V. Disconnect power, then measure the terminal resistance via the OBD port or ECU connector. The resistance must be 58-63Ω.
  • 5
    Sensor circuit impedance test: Disconnect the battery and unplug the ECU connector. Use a multimeter to measure the harness impedance of each crash sensor circuit (Front Impact Sensor, Side Impact Sensor). Normal impedance is 2.0-3.0 Ω (including sensor internal resistance). Infinity indicates an open circuit; <1 Ω indicates a short circuit.
  • 6
    Software flash attempt: Use BYD VDS or Launch X431 to enter the SRS system, execute the 'Control Unit Programming/Matching' function, and attempt to flash the ECU firmware (applicable to soft faults caused by program runaway or data corruption). Maintain battery voltage >13V during the flash.
  • 7
    ECU Replacement and Configuration: If all above checks are normal and DTC B1697-00 persists, replace the SRS ECU assembly (part number must match the vehicle model configuration code) and perform the following: a) Write the vehicle VIN; b) Configure vehicle model parameters (number of airbags, seat belt pretensioner type); c) Perform sensor calibration and system self-test.
  • 8
    Function check: Reconnect all connectors. Use the diagnostic tool to read fault codes and confirm B1697-00 is clear. Perform the 'Crash Output Test' (use special equipment to simulate the crash signal; do not test the airbag connector directly with a multimeter resistance setting). Confirm the instrument cluster airbag warning lamp turns off after the self-check and the system status displays 'Normal'.
Real-World Cases
BYD DTC AI Analysis

Resoldered dry joint on internal power supply chip of BYD Qin EV300 SRS ECU

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Vehicle: 2017 Qin EV300, 80,000 km Symptom: Instrument cluster airbag warning light illuminated intermittently. Scan tool read DTC B1697-00. Freeze Frame data indicated the fault occurred on bumpy roads. Diagnosis: ECU power supply measured normal. Tapping the ECU housing reproduced the fault. Opened the ECU (Caution: ESD-safe environment required; voids warranty) and found a cold solder joint on the LDO voltage regulator chip (5V to 3.3V) on the PCB. Repair: Re-soldered the joint using a hot air rework station, applied conformal coating, then reinstalled the ECU. Fault cleared. Total cost: ~200 yuan. Replacing the ECU costs over 2,000 yuan.
BYD DTC AI Analysis

Cleared B1697-00 locking fault on BYD Qin 80 after accident repair

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Vehicle: 2017 Qin 80, front-end collision repair. Symptom: After replacing the front bumper and wiring harness, the airbag warning light remained on with DTC B1697-00 present; unable to clear. Diagnosis: Inspection revealed bent pins in the front impact sensor connector causing a short circuit between the 12V power and signal lines. The ECU detected the circuit anomaly and activated protective lockout (Deployment Lock). Repair: Repaired the sensor wiring harness, accessed SRS special functions via VDS, executed 'Crash Data Clear' and 'ECU Unlock', and reconfigured sensor parameters. Fault resolved. Note: This procedure requires a manufacturer authorisation password or master technician privileges.
BYD DTC AI Analysis

Qin EV450 CAN bus poor contact causing ECU communication failure

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Vehicle: 2018 BYD Qin EV450, 50,000 km. Symptoms: Intermittent DTC B1697-00 with occasional "Check SRS System" warning. The fault code could be cleared but returned after several days. Troubleshooting: Power supply measured normal. Shaking the dashboard wiring harness caused the scan tool to lose communication with the ECU. Found the SRS ECU connector CAN-H terminal (normally pin 6) had backed out 1 mm, causing increased contact resistance (measured 5.6 Ω, normal <0.5 Ω). Repair: Reseated the terminal using a dedicated extraction tool, sprayed contact protector, reconnected the plug, and secured the harness with cable ties to prevent movement. Result: No recurrence after 3 months of monitoring.
BYD DTC AI Analysis

Qin 100: Software reflash after ECU data corruption from flat battery

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Vehicle: 2017 BYD Qin 100. Left unused for 3 months; battery deeply discharged (voltage <5V). After a jump-start, multiple warning lights came on on the dashboard. Fault symptoms: Alongside B1697-00, code B1698 (internal memory fault) appeared. Diagnosis: Charged battery, then measured voltage: 14.2V (normal). ECU power supply normal. Determined the low voltage caused EEPROM data write errors. Repair: Did not replace the ECU. Used VDS2000 to perform an 'airbag system software update', flashing the latest firmware (version typically includes a date code, e.g. V2.3.5). After flashing, performed 'system initialisation'. Fault codes cleared; system returned to normal. Recommended replacing the ageing battery.
BYD DTC AI Analysis

Replaced ECU on Qin EV due to internal oxidation after wading.

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Vehicle: 2017 BYD Qin EV300, driven through water approximately 40 cm deep. Symptoms: Airbag warning light on constantly, DTC B1697-00. Vehicle drives normally. Diagnosis: Inspected ECU mounting location beneath the centre console and found water staining. Disassembled ECU and found green corrosion on PCB concentrated around the acceleration sensor (MEMS chip) solder joints, causing internal reference voltage drift (measured 2.8 V, normal 3.3 V). Repair: Warranty does not cover water damage, and repair reliability is poor. Replaced SRS ECU assembly with a new unit (Part No.: BYD-3638100-XX; verify configuration). After replacement, performed full system configuration and calibration, dried the interior wiring harness, and sealed the water entry points.
Other Seal 6 EV 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.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.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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.