AU
B1730

DTC B1730 indicates the airbag control unit (SRS ECU) detects a resistance of 0 ohms in the left second-row side airbag firing circuit (typically located inside the left B-pillar trim or on the side of the left second-row seat) — Seal U

Safety System

DTC B1730 indicates the airbag control unit (SRS ECU) detects a resistance of 0 ohms in the left second-row side airbag firing circuit (typically located inside the left B-pillar trim or on the side of the left second-row seat).

This indicates a short to ground in the firing circuit, damaged wiring harness insulation shorting to ground, or an internal short circuit in the airbag module inflator.

This fault forces the SRS system into fail-safe mode, preventing the left second-row side airbag from deploying during a side impact, and continuously illuminates the instrument cluster airbag warning light.

Unlike high resistance (open circuit), a 0-ohm resistance typically means current flows directly to ground without passing through the inflator.

This is a hard short circuit fault and requires immediate repair.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Left middle row side airbag module internal igniter short circuit failure (manufacturing defect, moisture ingress, or aging causing an internal bridge wire short circuit)
  • 2Water ingress into the airbag wiring harness connector or bent pins making contact (poor B-pillar trim panel sealing commonly allows rainwater seepage, causing a short circuit between connector terminals or to ground)
  • 3Wiring harness wear causes a short to body ground (frequent seat adjustment, B-pillar trim removal/installation, or modification work pinches the harness and wears through the insulation).
  • 4Improper procedures when installing aftermarket or modified equipment (e.g., fasteners piercing the wiring harness when installing seat covers or floor coverings, or improper wire splicing when adding seat heating or ventilation equipment)
  • 5SRS control unit internal detection circuit fault (less common; damaged control unit A/D conversion circuit causes a false 0 Ω reading)
What To Do
  • 1
    Safety preparation: Power down the vehicle, disconnect the battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use VDS or a dedicated diagnostic tool to read the fault code. Confirm B1730 is a current fault and will not clear. Record freeze frame data to check vehicle status at the time of the fault.
  • 3
    Visual inspection: Remove the left middle-row B-pillar lower trim panel or seat side cover. Check the airbag connector (usually yellow) for water ingress, corrosion, and deformed or loose pins. Check the wiring harness for damage or crush marks.
  • 4
    Resistance measurement: Disconnect the airbag module connector. Use a digital multimeter to measure the resistance between the two terminals on the airbag module side. The normal value is 2.0-3.0 Ω. If the resistance is 0 Ω or close to 0 Ω, replace the airbag module.
  • 5
    Harness insulation check: Disconnect the SRS control unit connector. Measure the resistance between the harness-side airbag circuit and body ground. The resistance must be greater than 1MΩ. If the resistance is too low, inspect the harness section by section, focusing on the harness routing inside the B-pillar trim panel and at the seat slide rail.
  • 6
    Short circuit repair: After locating wiring harness damage, repair it using heat-shrink tubing or electrical tape. Replace the wiring harness assembly if necessary. Ensure sufficient clearance between the wiring harness and metal body parts, and install a protective sleeve.
  • 7
    Refit and verify: Reconnect all connectors (listen for the locking click), reconnect the battery negative terminal, and clear the fault codes. Turn the ignition switch to ON, verify the instrument cluster airbag warning light goes out after 6 seconds, and perform an SRS system self-diagnosis to confirm no faults.
Real-World Cases
BYD DTC AI Analysis

Tang DM left second-row side airbag short circuit after wading through water

✓
Vehicle: 2021 BYD Tang DM. Symptom: The airbag warning light on the dashboard stayed on after the vehicle drove through water. Diagnosis: Connected VDS and retrieved DTC B1730 (current fault). Removed the left B-pillar lower trim panel and found the airbag connector (yellow plug) had visible water stains and verdigris corrosion inside. Resistance between the pins measured 0.2 Ω, forming a short circuit. Further inspection found the B-pillar weatherstrip had perished, letting rainwater in. Solution: Cleaned the connector thoroughly with electronic contact cleaner, dried it with compressed air, and applied conductive grease to prevent corrosion. Replaced the left second-row side airbag module (the old one had moisture damage). Repaired the B-pillar weatherstrip. Road tested for one week with no fault recurrence.
BYD DTC AI Analysis

Seat modification damaged wiring harness on Song MAX

✓
Vehicle: 2019 Song MAX. Symptoms: Airbag warning light came on the day after installing leather seat covers. Diagnosis: Read DTC B1730. Asked the owner and confirmed the recent seat cover installation. Removed and inspected the left middle row seat. Found the metal retaining ring for the seat cover had pierced the side airbag wiring harness, causing the ignition wire to short directly to ground on the seat frame. Repair: Cut out the damaged section and soldered in a replacement length of high-temperature insulated wire (cross-sectional area ≥0.5 mm²). Rewrapped with insulating tape, fitted corrugated tubing for protection, and rerouted the harness clear of the clip position. Cleared the fault codes and the system returned to normal.
BYD DTC AI Analysis

Internal short circuit in a batch of Yuan EV airbag modules

✓
Vehicle: 2019 BYD Yuan EV535. Symptoms: No accident history; airbag warning light suddenly illuminated during normal use. Diagnosis: DTC B1730. Resistance at the airbag module connector measured only 0.8Ω, well below specification (2.0–3.0Ω). With the module disconnected, wiring harness insulation to earth tested normal. Confirmed internal short circuit in the module. This production batch has a common quality defect. Repair: Ordered and replaced the left second-row side airbag module (part number requires VIN verification). After fitting the new module, resistance measured 2.4Ω. Cleared DTC and completed system configuration. Fault fully resolved.
BYD DTC AI Analysis

Qin Pro intermittent short circuit on rough roads

✓
Vehicle: 2020 Qin Pro (petrol) Symptoms: Airbag warning light occasionally illuminated on rough roads; functioned normally on smooth surfaces. Diagnosis: DTC B1730 indicated an intermittent fault. Static resistance measured normal. Flexing the wiring harness to simulate driving conditions revealed an improperly seated airbag connector under the left seat of the middle row. During driving on bumpy roads, the yellow connector housing contacted the body metal bracket, causing an intermittent short to ground. Repair: Re-seated the connector and ensured the locking tab fully engaged. Secured the wiring harness to the seat frame with cable ties to prevent movement. Wrapped insulating tape around the connector housing for added protection. Follow-up: No recurrence after one month.
BYD DTC AI Analysis

Tang II SRS control unit software false alarm

✓
Vehicle: 2021 Tang DM-i. Fault: After accident repair (left rear quarter panel sheet metal work), persistent DTC B1730. Replacing the airbag module did not fix it. Diagnosis: Measured new module resistance at 2.2 Ω (normal). Wiring harness insulation to earth normal. Suspected control unit issue. Checked technical service bulletin – this production batch had a software calibration defect, causing false low-resistance detection in cold temperatures. Solution: Updated SRS control unit software to latest version (V2.1 or above), performed sensor calibration, and cleared fault codes. Fault resolved, no hardware replacement needed.
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.