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B1696-00

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

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
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 Seal U 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.