AU
B1698

DTC B1698 indicates the airbag system electronic control unit (ACU/SRS ECU) detects an internal system fault or critical function failure — Qin Plus

Safety System

DTC B1698 indicates the airbag system electronic control unit (ACU/SRS ECU) detects an internal system fault or critical function failure.

This fault involves an ECU internal processor self-check anomaly, memory data checksum error, power supply monitoring circuit fault, firing circuit diagnostic system anomaly, or interrupted communication with the vehicle CAN network.

As the core control module of the passive safety system, the SRS ECU monitors crash sensor signals in real time and controls the firing circuits for multiple airbags and seat belt pretensioners.

When B1698 triggers, the system typically enters fail-safe mode and automatically disables all airbag and pretensioner deployment.

This causes a complete loss of vehicle crash protection capability and poses a severe safety hazard.

The B1698 fault code on the Qin Plus indicates a critical internal failure within the airbag control unit (SRS ECU), such as a processor error, memory corruption, or power supply issue, rated as medium severity. Common causes include ECU hardware damage or voltage problems (battery too low/high, poor connections). Visit an authorised dealer immediately for diagnosis and repair. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1SRS ECU internal hardware fault: Damaged internal processor, EEPROM data corruption, power management chip failure, or internal capacitor aging causing unstable operating voltage.
  • 2Power supply system fault: battery voltage too low (<9V) or too high (>16V), loose connection in the ECU constant power/ignition power circuit, poor contact at fuse F1/FB07, corroded ground wires G103/G303 increasing contact resistance (>1Ω)
  • 3CAN communication bus fault: Lost communication with the Gateway Controller (GWC), CAN-H and CAN-L lines shorted to ground or power, wiring harness open circuit, or abnormal terminating resistor (120Ω) causing network failure.
  • 4Ignition circuit short/open circuit: A short to ground or power in the driver/passenger airbag, side airbag, seat belt pretensioner, or crash sensor wiring causes the ECU to trigger the protection mechanism and record an internal fault.
  • 5Corrupted software or calibration data: Control unit flashing failure, electromagnetic interference causing Flash data errors, prolonged vibration causing memory bit flips, or Event Data Recorder (EDR) overflow after a vehicle collision.
What To Do
  • 1
    Use VDS2000 or a dedicated BYD diagnostic tool to read the complete DTC list and record the freeze frame data. Check specifically for accompanying U-class communication fault codes (such as U0151, U0164) and save screenshots of the data stream.
  • 2
    Check the SRS ECU power supply and ground: Disconnect the battery negative terminal for 3 minutes, then unplug the ACU connector (usually located under the center console or behind the center armrest box). Measure the voltage at Pin 30 (constant power B+) and Pin 28 (ignition power IG1); the voltage must be 9-16V. Measure the resistance between Pin 24 (ground GND) and body ground; the resistance must be <1Ω. Inspect the connector for water ingress, pin corrosion, or backed-out terminals.
  • 3
    Check the CAN communication circuit: Measure resistance between diagnostic connector pin 6 (CAN-H) and pin 14 (CAN-L). The resistance must be 60 ± 5 Ω (parallel value of terminating resistors). Measure voltage to ground: CAN-H must be 2.5-3.5 V and CAN-L must be 1.5-2.5 V. Check circuit continuity between ACU connector pin 14 (CAN-H) and pin 13 (CAN-L).
  • 4
    Check ignition circuit integrity: Use a multimeter to measure the insulation resistance to ground and power for each airbag, pretensioner, and crash sensor circuit. Resistance must be >10MΩ. Check the steering wheel clock spring, the yellow connector under the seat, and the B-pillar connector for loose connections or water ingress.
  • 5
    Perform ACU replacement and configuration: If wiring checks are normal but the fault code will not clear, replace the SRS ECU with one of the same part number. Use VDS to perform online programming (write the VIN, vehicle configuration code, and calibration data). Perform crash sensor zero-point calibration on applicable models.
  • 6
    System verification: Clear all fault codes, perform a system self-check (approx. 10 seconds), and confirm the SRS warning light turns off normally. Set the ignition switch to the ON position and verify the ACU voltage, internal status, and crash sensor status in the data stream are normal. Perform a road test to confirm there are no intermittent faults.
Real-World Cases
BYD DTC AI Analysis

Internal corrosion in SRS ECU due to water wading

✓
Model: 2020 Song MAX 1.5T. Symptoms: After driving through heavy rain and floodwater, the instrument cluster displayed ‘Please check airbag system’. VDS read DTC B1698 (current and cannot clear). Diagnosis: Removed and inspected the ACU under the centre console. Found clear water staining and copper corrosion inside the connector, and the ECU housing seal had deteriorated. ACU power supply measured normal, but CAN bus voltage showed abnormal fluctuation. Repair: Replaced the ACU with a new assembly. Cleaned the harness connector terminals with electronic cleaner, applied conductive grease, and re-wrapped for waterproofing. After replacement, ran online programming and system self-test. Fault fixed.
BYD DTC AI Analysis

Poor ground connection after accident repair caused the fault.

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Vehicle: 2019 Yuan EV535. Symptom: SRS warning light remained illuminated after front collision repairs, and the system stored DTC B1698. Diagnosis: Checked ACU supply voltage at 12.4V (normal), but measured 8.5Ω resistance between the GND pin and body ground (abnormal). Inspection revealed that during accident repairs, the technician failed to properly reinstall the ACU ground wire after removing the centre console. Damaged threads on the ground bolt caused a poor connection. Repair: Retapped the ground stud and installed the ground wire using a new M6 bolt with serrated washer. Ground resistance dropped to 0.3Ω. Cleared DTCs, and the system returned to normal.
BYD DTC AI Analysis

Prolonged battery drain caused ECU initialization failure

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Model: 2021 Tang DM 2.0T. Symptom: Vehicle left unused for three months drained the battery. After a jump start, the SRS warning light came on. Codes B1698 and historical U0151 were retrieved. Diagnosis: Battery voltage measured only 8.2V, with severe fluctuations during the jump start (voltage spiked between 9–15V). Inspection found the ACU repeatedly failed to initialise under low voltage, logging internal fault codes. Repair: Fitted a new battery, used a regulated power supply to maintain 13.5V, cleared all DTCs, and performed the ACU restart sequence (power disconnected for over 10 minutes). The fault has not returned.
BYD DTC AI Analysis

Aftermarket modification caused CAN bus interference fault

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Vehicle: 2020 Qin Pro DM. Symptoms: After installing a large-screen aftermarket navigation system, the SRS system intermittently set DTC B1698; the fault appeared sporadically. Diagnosis: Checked ACU power and ground – normal. The CAN bus waveform showed significant noise. Inspection found the installer damaged the original SRS CAN harness shielding when pulling wires and did not twist the wires, causing interference from the audio amplifier’s high current. Repair: Repaired the damaged CAN wiring, restored the twisted-pair configuration (33–35 twists per metre), rewrapped the harness with aluminium foil shielding, grounded the shield at one end, and routed the harness away from the audio power cables. After the repair, the CAN waveform returned to normal and the fault cleared.
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.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.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.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.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 Qin Plus →Qin Plus 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.