AU
B1698-00

B1698-00 indicates the airbag system electronic control unit (SRS ECU) detects an internal fault or critical function abnormality — Atto 8

Safety System

B1698-00 indicates the airbag system electronic control unit (SRS ECU) detects an internal fault or critical function abnormality.

This fault code typically indicates an SRS ECU internal memory error, processor fault, power supply voltage out of operating range (overvoltage or undervoltage), or a persistent communication bus fault between the ECU and the crash sensors or airbag modules.

In BYD Qin series vehicles, this fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel airbag warning lamp.

During a collision, the vehicle may fail to deploy the airbags and seat belt pretensioners, posing a severe safety hazard.

This fault code is a hard fault that does not clear automatically and requires professional diagnosis and repair.

The B1698-00 fault code on the Atto 8 indicates an internal fault in the airbag system control unit (SRS ECU), such as memory errors, processor issues, or power supply problems. Severity is medium. Common causes include unstable battery voltage, blown fuses, or poor ground connections. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available based on recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1SRS ECU power supply circuit fault: unstable battery voltage, blown fuse (e.g., SRS-dedicated fuses F1/14, F1/15), poor power supply circuit connection, or excessive voltage drop.
  • 2Poor ground connection: Loose, oxidized, or corroded SRS ECU ground terminal (usually located on the instrument panel frame or under the A-pillar) causing excessive ground resistance (standard: < 1Ω).
  • 3SRS ECU internal hardware fault: internal capacitor aging, memory data corruption, microprocessor malfunction. Common in early-batch 2017-2018 Qin series models.
  • 4CAN bus communication fault: A short circuit, open circuit, or electromagnetic interference in the communication line between the SRS ECU and the vehicle CAN network prevents normal ECU operation.
  • 5External sensor or actuator short circuit: An internal short circuit in the front collision sensor, side airbag sensor, or airbag module pulls down the SRS ECU reference voltage and triggers an ECU protective fault code.
What To Do
  • 1
    Safety check and preliminary inspection: Disconnect the high-voltage service disconnect (MSD) and wait 5 minutes for the high-voltage system to discharge. Disconnect the battery negative terminal and wait at least 3 minutes for the SRS capacitor to fully discharge to prevent accidental airbag deployment.
  • 2
    Visual inspection: Inspect the SRS ECU for physical damage, water stains, or burn marks. Inspect the SRS ECU wiring harness connector located under the dashboard or in the center tunnel (usually 24-48 pins) for looseness, backed-out pins, or corrosion.
  • 3
    Power and ground measurement: Reconnect the battery and turn the ignition switch to ON. Use a multimeter to measure the voltage at the SRS ECU connector power terminals (constant power +B and ignition switch IG wire); the voltage should be 11-14V. Measure the resistance between the ground terminal and the vehicle body ground; the resistance should be less than 1Ω.
  • 4
    Scan tool deep diagnosis: Use the BYD VDS or Launch X-431 scan tool to access the SRS system. Read the complete fault code freeze frame data and confirm if B1698-00 is a history or current code. Check for accompanying communication fault codes (e.g., U-codes).
  • 5
    Wiring harness continuity test: Disconnect the SRS ECU and crash sensor connectors. Measure the continuity and insulation of the CAN-H, CAN-L, and sensor power wires between them. Confirm no short to ground or power. Wiring harness resistance must be less than 2Ω.
  • 6
    Software and configuration check: Verify the SRS ECU software version is up to date. Compare with the BYD Technical Service Bulletin (TSB). Update the software or reconfigure the coding if necessary.
  • 7
    Component Replacement and Verification: If all above checks are normal, replace the SRS ECU with a unit of the same part number (Note: older Qin series ECUs may require VIN matching). After replacement, perform the airbag system self-check cycle test. Confirm the fault code does not return and the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 airbag warning light suddenly came on while driving.

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Vehicle: 2017 Qin EV300, 42,000 km, no accident history. Symptoms: Airbag warning light suddenly illuminated during normal driving. VDS read DTCs B1698-00 (SRS ECU fault) and B1694-00 (power supply voltage low). Diagnosis: Measured SRS ECU power supply terminals and found IG power voltage fluctuating between 8.5V and 11V — abnormal. Traced the wiring harness and discovered a loose harness retaining clip under the dashboard. The harness had been rubbing against the steering column metal bracket over time, damaging the insulation and partially breaking the copper wires, causing high resistance. Repair: Repaired the damaged harness, re-secured the harness routing, and measured voltage restored to 12.4V. Cleared fault codes, the airbag light went out, and the system returned to normal.
BYD DTC AI Analysis

BYD Qin 100 SRS failure after wading though water

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Vehicle: 2017 BYD Qin 100. After driving through heavy rain and floodwater, the instrument cluster displayed "Check Airbag System." Symptoms: The vehicle waded through approximately 30 cm of water. The airbag warning light then stayed on constantly. The scan tool showed active fault code B1698-00. Diagnosis: Removed the SRS ECU from beneath the centre console. The ECU housing seal had deteriorated, with visible water stains and oxidation on the circuit board. Measured ECU power supply: normal, but the internal CAN transceiver pins were shorted to earth. Solution: Fitted a new SRS ECU (part number: BYDEG-3658100). Replaced the wiring harness seal. Dried and applied corrosion protection to the surrounding wiring harness. Performed ECU coding. Fault resolved.
BYD DTC AI Analysis

Intermittent B1698-00 fault on Qin EV450

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Vehicle: 2018 Qin EV450. Fault intermittent, more likely during cold starts. Symptoms: The airbag warning light occasionally came on during morning startup and sometimes went off after driving for a while. VDS scan showed historic DTC B1698-00. Diagnosis: During continuous monitoring, I found the SRS ECU earth voltage was 1.2V when the fault occurred (normal: <0.1V). I inspected the earth wire and found the earth point beneath the A-pillar. The mounting bolt was loose, and the contact surface had paint and oxidation. Repair: I sanded the earth point contact surface to bare metal, reinstalled the earth bolt, and tightened it to standard torque (typically 8-10N·m). Earth resistance dropped to 0.3Ω after the repair. I monitored the vehicle for a week; the fault did not return.
Other Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.