AU
B1697-00

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

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.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Thermal fatigue causing dry solder joints or breakdown of the SRS ECU internal power supply IC (such as TLE7263 or similar automotive-grade voltage regulator chip), dropping the core supply voltage below 3.0V (normal: 3.3V±0.1V).
  • 2A voltage surge (>16V) generated during vehicle battery discharge or jump-starting damages the internal ECU EEPROM data block or causes a checksum error.
  • 3Front/side impact sensor circuit short to ground or power (impedance <1Ω or >5Ω). The ECU activates protective lockout and records an internal fault.
  • 4Short circuit between the diagnostic CAN bus lines (CAN-H and CAN-L) or abnormal terminating resistance (outside 60Ω±5%) causes a communication timeout between the ECU and the vehicle network, triggering a watchdog reset failure.
  • 5ECU housing seal failure allows moisture ingress and internal PCB oxidation (common in flooded or high-humidity areas), causing intermittent short circuits in key 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 (verifying SRS backup capacitor voltage <1V). Do not connect or disconnect airbag-related wiring harnesses with the power on.
  • 2
    Visual and connection inspection: Remove the trim panel below the center console and inspect the SRS ECU connector (typically a 24-pin or 32-pin black plug) for looseness, backed-out pins, green corrosion, oxidation, or signs of water ingress. Measure the terminal retention force.
  • 3
    Power and ground verification: Reconnect the battery (do not unplug the ECU connector). Use a multimeter to measure the ECU connector terminals: constant power (BATT, 30#) should be 12V±0.5V; ignition power (IGN, 15#) should be 12V in the ON position; ground wire (GND) resistance to the vehicle body should be <1Ω, and voltage drop should 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. Power off the vehicle, 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 2.0-3.0Ω (including sensor internal resistance). Infinity indicates an open circuit; <1Ω indicates a short circuit.
  • 6
    Software flash attempt: Use BYD VDS or Launch X431 to access 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: a) Write the vehicle VIN; b) Configure vehicle parameters (number of airbags, seat belt pretensioner type); c) Perform sensor calibration and system self-test.
  • 8
    Function check: Restore all connections. Use the diagnostic tool to read fault codes and confirm B1697-00 is clear. Perform the 'Crash Output Test' (requires special equipment to simulate the crash signal; do not use a multimeter resistance range to test the airbag connector directly). 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

✓
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.

✓
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 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.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.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.
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.