AU
B1717-00

This DTC indicates the SRS (Supplemental Restraint System) ECU detected an open circuit or disconnected condition in the left knee airbag module (Driver Knee Airbag Module) during self-diagnosis — Seal U

Safety System

This DTC indicates the SRS (Supplemental Restraint System) ECU detected an open circuit or disconnected condition in the left knee airbag module (Driver Knee Airbag Module) during self-diagnosis.

Specifically, when the SRS ECU sends a test signal to the left knee airbag igniter circuit, it fails to receive a normal circuit response or detects a circuit resistance exceeding the normal threshold (typically infinite or extremely high resistance).

Consequently, the left knee airbag may fail to deploy during a collision, resulting in a loss of lower limb protection for the driver.

Additionally, the SRS enters fail-safe mode and continuously illuminates the instrument cluster airbag warning light.

The system may also lock the deployment function of the entire airbag system, severely compromising passive safety performance.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Knee airbag module connector loose, not fully seated, or locking tab damaged, causing poor pin contact or complete disconnection.
  • 2Open circuit, short to ground, or short to power in the wiring harness between the SRS ECU and left knee airbag module.
  • 3Left knee airbag module internal igniter open circuit or abnormal resistance (too high or too low)
  • 4Connector terminal oxidation, corrosion, or back-out causing increased contact resistance.
  • 5Improper airbag module installation or crushed wiring harness after collision repairs or instrument panel removal and installation.
What To Do
  • 1
    Safety preparation: Set the power mode to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor.
  • 2
    Visual inspection: Remove the driver-side knee trim panel and verify the left knee airbag module connector is fully seated. Confirm the locking tab is intact and secure.
  • 3
    Circuit measurement: Use a multimeter to measure the harness resistance between the SRS ECU and the knee airbag module (should be less than 1 Ω). Measure the harness resistance to ground (should be greater than 1 MΩ) and voltage to ground (should be less than 1 V).
  • 4
    Component replacement test: Disconnect the original airbag module, connect a known-good left knee airbag module (or simulated load), and read the fault code to confirm if the module is faulty.
  • 5
    Connector handling: If pins are oxidized, clean with electrical contact cleaner and apply conductive grease. If the locking tab is damaged, replace the connector or repair the wiring harness.
  • 6
    System reset: Reconnect all components, turn on the power, and use the diagnostic tool to clear the fault code. Wait 20 seconds, then read the fault codes again to verify B1717-00 does not return.
  • 7
    Function verification: Perform the SRS system self-check. Confirm the airbag warning light turns off after the self-check and the system returns to normal.
Real-World Cases
BYD DTC AI Analysis

Loose connector on left knee airbag causing 'not connected' fault

✓
A 2017 BYD Qin EV300's airbag warning light stayed on. Read DTC B1717-00. Found that during a cabin air filter replacement at an independent shop, removing and refitting the lower dash trim had loosened the left knee airbag connector. After firmly reconnecting the connector and confirming the retaining clip was fully seated, cleared the DTC and the system returned to normal.
Original source ↗
BYD DTC AI Analysis

Knee airbag module damaged after accident repair

✓
After front collision repair on a 2017 Qin 100, the SRS warning light stayed on. The diagnostic scanner showed DTC B1717-00. Inspection found the left knee airbag module had not deployed, but impact from the accident caused an open circuit in the internal igniter. The module showed infinite resistance. Replacing the left knee airbag module resolved the fault.
Original source ↗
BYD DTC AI Analysis

Wiring harness chafing caused intermittent open circuit

✓
A 2018 BYD Qin EV450 had an intermittent airbag warning light; fault code B1717-00 would come and go. I found the driver's side knee area wiring harness had chafed through from prolonged steering movement, damaging the insulation and partially breaking some internal copper wires. I repaired the harness and fitted an anti-chafe sleeve, which completely resolved the fault.
BYD DTC AI Analysis

Oxidised connector pins causing poor contact

✓
A high-mileage Qin 80 logged DTC B1717-00 after use in humid conditions. Disassembly inspection found green oxidation on the left knee airbag connector pins, increasing contact resistance (measured 15 Ω; normal: <1 Ω). Cleaned the pins and applied conductive grease. Resistance returned to normal, then cleared the fault code.
Original source ↗
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.