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B1696-00

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

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.

The B1696-00 fault code on the Qin Plus indicates an internal hardware or software fault in the airbag control unit (SRS ECU), preventing it from performing crash detection and deployment functions. Severity is medium. Common causes include failed solder joints or aging components from heat and vibration, or collision damage to internal chips. Repair requires visiting an authorised dealer. Typical repair cost data is available from 3 recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Cold or broken solder joints on the ECU internal circuit board, or aging and failure of key components (capacitors, resistors, chips), commonly occurring after 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 the internal ECU chip or data memory.
  • 3Power system fault (such as incorrect jump-starting, voltage surge, or reversed battery polarity) causing breakdown of the internal ECU power management module.
  • 4ECU software data corruption or loss (e.g., interrupted flashing or EEPROM data checksum failure) causes the self-check program 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) and G36-33 (IGN power); the standard value is 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 the 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 electronic contact cleaner and apply conductive paste.
  • 5
    Perform a power reset: disconnect the battery negative cable for at least 5 minutes, reconnect it, start the vehicle, and observe if the fault code reappears.
  • 6
    If the fault persists, the internal ECU hardware is damaged. 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, vehicle configuration parameters, match sensor IDs, etc.) to ensure it matches the vehicle immobilizer and network systems.
  • 8
    Clear all fault codes and perform the SRS system self-check (turn the ignition switch to ON and observe whether 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 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.