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 — Atto 3

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
5
Causes
Likely Causes — Atto 3
  • 1Airbag module internal igniter short circuit: A broken igniter bridge wire inside the curtain airbag or a damp pyrotechnic charge causes a short circuit between the two terminals, reducing the 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 in the yellow SRS connector below the A-pillar causes direct contact between the positive and negative terminals.
  • 4SRS ECU internal drive circuit fault: A damaged airbag driver chip or sampling resistor inside the ECU causes a false short circuit fault.
  • 5Improper repair procedures: Unqualified technicians directly measuring across the airbag terminals with a low-impedance multimeter, or causing a short circuit by touching the terminals with metal tools during removal.
What To Do
  • 1
    Safe power-down and discharge: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and 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 pinch marks. Check the connectors for water ingress, corrosion, or looseness.
  • 3
    Isolation diagnosis: Disconnect the left front curtain airbag connector (usually located below the A-pillar). Use a high-impedance digital multimeter to measure resistance on the wiring harness side. If resistance is 0, the fault is in the wiring harness or ECU. If resistance is infinite, the fault is in the airbag module.
  • 4
    Harness continuity test: Test the harness between the SRS ECU and the airbag connector for a short to ground (measure the resistance between the terminal and body ground), and check for a short circuit between the 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 confirm 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 and perform an SRS system self-check. Confirm B175D1A does not return and the airbag warning light turns 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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.