AU
B1696-00

DTC B1696-00 indicates an internal hardware or software fault in the airbag electronic control unit (SRS ECU) — Atto 3

Safety System

DTC B1696-00 indicates an internal hardware or software fault in the airbag electronic control unit (SRS ECU).

This fault points to an abnormality in the ECU internal microprocessor, memory (EEPROM), power management module, or internal communication bus, preventing the ECU from completing self-checks or running safety algorithms normally.

This fault is a current hard fault (Present DTC), meaning the ECU has detected substantial internal damage and cannot perform normal crash detection and airbag deployment decision functions.

While the fault is present, the airbag system may enter fail-safe mode (fully disabled or partially restricted).

In a collision, the airbags may fail to deploy properly, creating a severe safety hazard.

This fault differs from external wiring or sensor faults; repairing the wiring harness will not resolve it.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Cold or broken solder joints on the internal ECU circuit board, or aging and failure of key components (capacitors, resistors, chips), commonly resulting from exposure to high temperatures or prolonged vibration.
  • 2During a vehicle collision, even if the airbag does not deploy, high surge current or mechanical stress may physically damage internal ECU chips or data memory.
  • 3Power system fault (such as incorrect jump-starting, voltage surge, or reversed battery polarity) causing breakdown of the ECU internal power management module.
  • 4Corrupted or missing ECU software data (e.g., interrupted flashing or EEPROM data checksum failure) causes the self-test routine to fail.
  • 5Prolonged water ingress or moisture in the ECU connector causes pin oxidation and corrosion, leading to internal short circuits or abnormal signals (indirectly damaging the ECU).
What To Do
  • 1
    Use a dedicated diagnostic tool (such as BYD ED400 or Launch X431) to read SRS system fault codes, confirm B1696-00 is a current fault (Active), and record history fault codes.
  • 2
    Check the SRS ECU power supply circuit: Disconnect connector G36. Measure the voltage at G36-34 (constant power supply) and G36-33 (IGN power supply). Standard value: 11-14V. Measure the resistance between G36-35 (ground) and body ground. The resistance must be less than 1Ω.
  • 3
    Check CAN bus communication: Measure voltage to ground and terminal resistance at G36-20 (CAN-H) and G36-40 (CAN-L). Confirm no U-class communication fault codes are present.
  • 4
    Visually inspect the ECU connector and wiring harness for signs of water ingress, oxidation, or corrosion. If necessary, clean with electrical contact cleaner and apply conductive grease.
  • 5
    Perform a power reset: Disconnect the battery negative cable for at least 5 minutes. Reconnect the cable, start the vehicle, and observe if the fault code reappears.
  • 6
    If the fault persists, the ECU has an internal hardware failure. Replace the SRS ECU assembly. Note: Record the original ECU coding information before replacement.
  • 7
    After installing the new ECU, use the diagnostic tool to perform online programming or offline configuration (write the VIN and vehicle configuration parameters, perform sensor ID matching, etc.) to synchronize the ECU with the vehicle immobilizer and network systems.
  • 8
    Clear all fault codes and perform the SRS system self-check (turn the ignition switch to the ON position and observe if the instrument cluster airbag warning light illuminates for 6 seconds and then turns off). Perform a road test to verify.
Real-World Cases
BYD DTC AI Analysis

BYD Qin - Airbag warning light stays on with internal ECU fault

✓
After starting the vehicle, the airbag warning light on the instrument panel stayed on. Scanned the system and retrieved DTC B1696-00 (current fault); the code would not clear. Per the workshop manual, checked the SRS ECU connector G36 power supply (G36-34 voltage 12.3V) and ground (G36-35 resistance 0.3Ω); both readings normal. CAN bus communication showed no faults. Attempted a power reset and recoding without success. Diagnosed internal processor failure in the ECU. Replaced the airbag control unit (SRS ECU) with a new unit, then performed coding and configuration using a dedicated diagnostic tool. The warning light went out and the system self-check returned normal.
Original source ↗
BYD DTC AI Analysis

BYD E5 - Airbag system warning after accident repair

✓
The vehicle had a front-end collision. After the workshop replaced the front bumper, crash sensors and airbags, the airbag warning light stayed on. The scan tool detected DTC B1696-00 and multiple stored sensor faults. After clearing the history codes, only B1696-00 could not be cleared. The technician checked the wiring harnesses and connectors for each new sensor—no shorts or open circuits. The SRS ECU power supply and ground tested normal. The technician determined that a current surge from the impact damaged the chip inside the SRS ECU. The workshop replaced the airbag control unit assembly and performed online configuration (writing the vehicle VIN and matching parameters). The fault cleared and the airbag light went out.
Original source ↗
BYD DTC AI Analysis

BYD Song – Intermittent airbag warning light (intermittent fault)

✓
The owner reported that the airbag warning light would occasionally come on when driving on rough roads or in rain, sometimes turning off after restarting. A diagnostic scan captured historic DTC B1696-00 with intermittent status. Initial inspection of the SRS ECU connector G36 found slight oxidation and water ingress. After cleaning the connector and applying conductive grease, we road tested the vehicle, but the fault returned two days later. Checking the ECU power supply showed no abnormal voltage fluctuations during vehicle vibration. Based on the DTC definition, we determined the control unit had internal dry solder joints or aging components, triggering the fault under certain conditions (vibration and temperature changes). We replaced and reprogrammed the SRS ECU, and added a waterproof boot to the connector to seal it against moisture. This permanently fixed the fault.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.