AU
B1740-00

This DTC indicates that during the self-check, the SRS (Supplemental Restraint System) control module detects, through its internal diagnostic circuit, an open circuit in the left rear side airbag (left curtain airbag or seat side airbag) communication line, or the airbag module initialization resistance falls outside the normal range (typically 2 — Seal 6 EV

Safety System

This DTC indicates that during the self-check, the SRS (Supplemental Restraint System) control module detects, through its internal diagnostic circuit, an open circuit in the left rear side airbag (left curtain airbag or seat side airbag) communication line, or the airbag module initialization resistance falls outside the normal range (typically 2.0-3.0 ohms).

Consequently, the SRS module cannot confirm the physical presence or electrical connection integrity of the airbag, and the system registers the airbag as "not present".

In a collision, this airbag may fail to deploy, disabling side impact protection for the left rear passenger.

Additionally, the SRS system enters fail-safe mode, which may alter the deployment logic of the entire airbag system and illuminate the instrument cluster airbag fault warning lamp.

The B1740-00 fault code on the Seal 6 EV indicates a medium-severity SRS fault where the left rear side airbag circuit is open or its resistance is out of range, so the system may treat the airbag as not present. This could prevent deployment in a side impact. Common causes include a loose rear airbag connector or an internal airbag igniter fault. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Loose, disconnected, or poor contact at the left rear side airbag wiring harness connector (common after seat adjustment, B-pillar trim removal/installation, or being kicked by rear passengers)
  • 2Airbag module internal igniter open circuit or abnormal resistance (internal airbag fault or aging)
  • 3Open circuit, short circuit from chafing, or short to ground in the wiring harness between the SRS module and the left rear airbag (repeated flexing at the seat track or B-pillar sill breaks the copper wires).
  • 4SRS control module internal diagnostic circuit fault (outdated software version or damaged hardware sampling circuit)
  • 5The vehicle previously experienced a side impact, wading, or flooding, causing corrosion or water ingress at the airbag connector, or damage to the wiring harness insulation.
What To Do
  • 1
    Use the BYD VDS or a dedicated diagnostic tool to read the fault code. Confirm B1740-00 is a current fault (Current DTC) rather than a history fault, and check the voltage and ambient temperature in the freeze frame data.
  • 2
    Disconnect the battery negative terminal and wait at least 90 seconds to discharge the residual charge in the SRS capacitor to ensure safe operation and prevent accidental airbag deployment.
  • 3
    Locate the left rear side airbag (on Qin series models, typically inside the left B-pillar trim panel or on the side of the left rear seat). Verify the yellow dedicated connector is fully locked. Inspect the terminals for oxidation, backout, or deformation.
  • 4
    Use a multimeter to measure the airbag wiring harness continuity: the circuit resistance between the SRS module connector and the airbag connector must be less than 1 ohm, the insulation resistance to ground must be greater than 1M ohm, and the short-to-power check must read 0V.
  • 5
    Measure the airbag module resistance (via wiring harness or direct connection). The standard value is 2.0±0.3 ohms. High resistance indicates an open circuit; low resistance indicates a short circuit. If the resistance is abnormal, replace the airbag assembly.
  • 6
    If the wiring harness has an open or short circuit, repair and rewrap the harness. If the connector is damaged, replace the dedicated yellow airbag connector and verify the locking tab is secure.
  • 7
    Reconnect all connectors and install the 12V battery negative terminal. Use the diagnostic tool to clear the fault code and perform an SRS system self-check. Confirm the fault code does not return and the warning light turns off.
  • 8
    Verify airbag system function (use the diagnostic tool to read the live data stream and confirm the left rear side airbag status displays 'Normal' rather than 'Not Present').
Real-World Cases
BYD DTC AI Analysis

Seat adjustment dislodged the airbag connector

✓
A 2017 Qin EV300 had the airbag warning light on steady. Read fault code B1740-00. Inspection found that frequent forward and backward adjustment of the left rear seat by passengers had loosened the side airbag harness connector under the seat. Reconnected the connector and secured the harness clip, then cleared the code. The fault code did not return.
BYD DTC AI Analysis

B-pillar wiring harness wear caused an open circuit.

✓
2018 BYD Qin EV450 had DTC B1740-00. Removed the left rear B-pillar trim panel and found the curtain airbag wiring harness insulation had worn through at the junction between the B-pillar and the body sheet metal. Prolonged vibration had damaged the insulation, and some copper wires were broken, causing an intermittent open circuit. Repaired the harness, added an anti-chafing sleeve, and resolved the fault.
BYD DTC AI Analysis

Corroded airbag connector on water-damaged vehicle

✓
A 2017 Qin 100 drove through water and stored DTC B1740-00. Inspection found mud and water residue inside the left rear side airbag connector (yellow plug); green corrosion on the terminals caused high contact resistance (measured 8.5 ohms). After cleaning the terminals and applying electronic protectant, resistance returned to normal, resolving the fault.
BYD DTC AI Analysis

Internal igniter fault in airbag module

✓
2017 BYD Qin 80 repeatedly set B1740-00. Harness continuity checked normal; connectors OK. Direct resistance measurement at the left rear side airbag module: infinite (open circuit). Determined internal airbag igniter circuit open. Replaced left rear side airbag assembly. System self-test passed.
BYD DTC AI Analysis

SRS module coding error after accident repair

✓
After accident repairs, a Qin EV300 stored DTC B1740-00. A check found the repair shop had replaced the SRS control module but coded it incorrectly. This base model lacks rear side airbags, yet the module had high-spec coding. Recoding and reconfiguring the SRS module cleared the fault code.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.