AU
B175D1A

DTC B175D1A indicates the SRS (Supplemental Restraint System) ECU detects a resistance of 0 ohms or near 0 ohms in the left front side curtain airbag (head protection airbag) igniter circuit — Seal U

Safety System

DTC B175D1A indicates the SRS (Supplemental Restraint System) ECU detects a resistance of 0 ohms or near 0 ohms in the left front side curtain airbag (head protection airbag) igniter circuit.

Normal igniter resistance typically ranges between 2.0 and 3.0 ohms.

A resistance of 0 ohms indicates a short circuit (short to ground or short between wires), not an open circuit.

This short circuit prevents the SRS ECU from deploying the side airbag during a collision, or in extreme cases, abnormal current causes unintended airbag deployment.

The ECU continuously monitors this hard fault and illuminates the airbag warning light.

The system enters fail-safe mode, potentially limiting overall airbag system functionality.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Airbag module internal igniter short circuit: A broken igniter bridge wire inside the curtain airbag or moisture in the pyrotechnic charge causes a short circuit between the two terminals, reducing resistance to 0.
  • 2Wiring harness short to ground: A-pillar, B-pillar, or roof wiring harness rubs against the metal body during vehicle vibration, damaging the insulation and shorting the wire directly to ground.
  • 3Connector terminal short circuit: Water ingress, oxidation, or terminal deformation at the yellow SRS connector below the A-pillar causes direct contact between the positive and negative terminals.
  • 4SRS ECU internal drive circuit fault: Damaged airbag drive chip or sampling resistor inside the ECU triggers a false short circuit fault.
  • 5Improper repair procedure: Unqualified technician measuring directly across the airbag terminals with a low-impedance multimeter, or touching the terminals with a metal tool during removal, causing a short circuit.
What To Do
  • 1
    Safe power-off and discharge: Disconnect the 12V battery negative terminal. Wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment.
  • 2
    Visual inspection: Check the yellow SRS wiring harness sleeve inside the left A-pillar, B-pillar, and headliner trim panels for wear or compression marks. Inspect the connectors for water ingress, corrosion, or looseness.
  • 3
    Isolation diagnosis: Disconnect the left front curtain airbag connector (usually located below the A-pillar). Measure the resistance on the wiring harness side using a high-impedance digital multimeter. If the resistance is 0, the fault is in the wiring harness or ECU. If the resistance is infinite, the fault is in the airbag module.
  • 4
    Harness continuity test: Check the wiring harness between the SRS ECU and the airbag connector for a short to ground (measure the resistance between the terminal and body ground). Check for a short circuit between the harness wires (measure the resistance between the positive and negative wires).
  • 5
    Airbag module test: If the wiring harness is normal, replace the curtain airbag module (do not measure airbag module resistance to prevent deployment).
  • 6
    ECU replacement test: If the wiring harness and airbag are normal, replace the SRS ECU with a known good unit to determine if the ECU internal detection circuit is faulty.
  • 7
    System reset and verification: After repair, restore all connections and install the battery. Use the diagnostic tool to clear the fault code. Perform an SRS system self-check. Confirm B175D1A does not return and the airbag warning light is off.
Real-World Cases
BYD DTC AI Analysis

A-pillar wiring harness chafing caused intermittent short circuit

✓
A 2019 BYD Qin EV presented with an intermittent SRS warning light. Scanning revealed DTC B175D1A. Inspection found obvious signs of previous removal on the left A-pillar trim. Removing the trim revealed the curtain airbag harness had chafed through its insulation at the A-pillar corner, exposing bare copper wires that contacted the metal bodywork and shorted to earth. Repair: Wrapped the damaged section with insulation tape, rerouted the harness to avoid contact with sharp edges, and refitted the harness clips. No recurrence at one-month follow-up.
BYD DTC AI Analysis

Sunroof drain hose leak corroded connector

✓
A BYD E2 airbag warning light stayed on after driving in the rain with DTC B175D1A. Inspection found the left front side curtain airbag connector beneath the A-pillar had water ingress from a detached sunroof drain tube, causing severe terminal oxidation and a short. Reattached the drain tube, cleaned the connector with electronic cleaner, blow-dried it, applied conductive grease, and replaced the connector terminals. Also checked carpet moisture to prevent subsequent corrosion.
BYD DTC AI Analysis

Replaced airbag module (internal short circuit)

✓
A 2020 E3 developed DTC B175D1A after accident repairs. The left front had sustained impact. The curtain airbag had not deployed but took impact. Disconnected the airbag connector and measured harness resistance as normal (infinite), indicating an internal igniter short in the module. Replaced the left front curtain airbag assembly (including gas generator and airbag cushion), performed SRS configuration and calibration, and cleared the fault. Even if airbags do not deploy on accident vehicles, check the internal igniter status.
BYD DTC AI Analysis

SRS ECU false alarm resolved with software update

✓
Multiple 2019 Qin EVs reported DTC B175D1A, but wiring harness and airbag resistance tested normal. BYD confirmed via Technical Service Bulletin that early batch SRS ECU software has a sampling circuit fault, causing false short-circuit detection in low temperatures. Solution: Upgrade the SRS ECU software to a version higher than V2.3. The fault code clears automatically after the upgrade; no hardware replacement needed. Check manufacturer TSBs.
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.