AU
B175B-00

DTC B175B-00 indicates the SRS (Supplemental Restraint System) control unit detects the right rear side airbag igniter circuit resistance (typically located in the right rear seat side or C-pillar trim panel) falls below the manufacturer threshold (normal range: 1 — Atto 3

Safety System

DTC B175B-00 indicates the SRS (Supplemental Restraint System) control unit detects the right rear side airbag igniter circuit resistance (typically located in the right rear seat side or C-pillar trim panel) falls below the manufacturer threshold (normal range: 1.8–3.0 Ω; fault condition: below 1.0 Ω or near 0 Ω).

This constitutes a low-resistance airbag circuit fault, meaning the control unit identifies a short circuit risk (wiring harness short to ground, wire-to-wire short, or internal short within the airbag module).

Consequently, the affected side airbag may fail to deploy during a collision (as the ECU interrupts the trigger signal due to the circuit anomaly) or, in extreme cases, deploy unintentionally.

Simultaneously, the SRS system illuminates the instrument cluster airbag warning light and may disable the entire airbag system to protect occupants.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Right rear side airbag module internal igniter short circuit: Manufacturing defects, aging, or moisture ingress cause abnormally low resistance in the airbag internal igniter wire.
  • 2Wiring harness worn and shorted to ground: Seat adjustment mechanism, seat belt anchor point, or body sheet metal edge rubbed through the harness insulation, causing the wire to ground to the vehicle body.
  • 3Connector water ingress and corrosion: Vehicle wading, blocked sunroof drain tubes, or aging seals allow water to enter the lower right B/C-pillar airbag connector (usually located under the seat or at the base of the C-pillar). This causes electrolytic corrosion between the pins, forming a low-resistance path.
  • 4Improper seat modification or repair: When replacing seat covers, installing seat heaters, or adjusting the seat, fixing screws crush the wiring harness, or an incompletely locked connector causes abnormal terminal contact.
  • 5SRS control unit internal sampling circuit fault: Internal ECU A/D converter or monitoring chip failure causes a false low resistance reading (rare; confirm after excluding external wiring).
What To Do
  • 1
    Safety preparation: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 3 minutes (or follow workshop manual requirements to ensure the SRS capacitor fully discharges) to prevent accidental airbag deployment during repair.
  • 2
    Data confirmation: Connect the VDS2000/DiLink diagnostic tool, enter the SRS system, read the live data stream, and confirm the right rear side airbag resistance is below the standard value (record the specific resistance value, such as 0.3Ω or 0.0Ω).
  • 3
    Visual inspection: Remove the right rear seat (if applicable) and lower C-pillar trim panel. Check the airbag wiring harness connector (usually a yellow plug) for looseness, water ingress, pin corrosion, or foreign objects.
  • 4
    Module isolation test: Disconnect the right rear side airbag connector. Connect a dedicated airbag simulator (resistor, usually 2.0Ω) to the wiring harness side. Power on the vehicle and read the fault codes. If the fault changes to "open circuit" or the resistance is normal, the airbag module is faulty. If the resistance remains too low, the fault lies in the wiring harness or the ECU.
  • 5
    Harness continuity test: Disconnect the airbag module and SRS ECU connectors. Use a multimeter to measure harness terminal-to-ground resistance (should be >1MΩ) and the resistance between the two harness wires (should be >1MΩ). Check for short circuits.
  • 6
    Wiring harness insulation check: Inspect the wiring harness routing, especially where it passes through the seat frame and floor pan holes. Check for damaged insulation. If necessary, repair the wiring harness and install corrugated conduit for protection.
  • 7
    Component replacement: If testing confirms an internal short circuit in the airbag module, replace the right rear side airbag module; if testing confirms a short circuit in the wiring harness, repair or replace the wiring harness; if testing confirms an ECU fault, replace the SRS control unit and perform coding and matching.
  • 8
    System verification: After repair, clear the fault code and perform static and dynamic tests (including a simulated crash signal test to verify the system correctly identifies the circuit status). Confirm the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Right rear seat adjuster chafed through wiring harness, causing short circuit

✓
2017 BYD Qin EV300, 80,000 km. Airbag warning light on; DTC B175B-00. Inspection found the right rear seat rail wiring harness rubbing against the seat adjustment mechanism's metal edge. Long-term friction wore through the insulation, exposing two bare wires that contacted and shorted. Repair: Wrapped the damaged section with insulation tape, rerouted the harness, added corrugated tubing, and secured with cable ties to prevent interference with moving parts. Fault cleared.
BYD DTC AI Analysis

C-pillar connector corroded after water wading, causing low resistance

✓
Qin EV450 airbag warning light triggered after wading through heavy rain. Scan tool showed right rear side airbag resistance at 0.8Ω (low). Removed lower right C-pillar airbag connector and found water staining and green copper corrosion inside. Cause: Sunroof drain hose connector deteriorated and detached, letting rainwater run down the A-pillar, across the floor and into the C-pillar. Repair: Cleaned connector pins with electrical contact cleaner, applied conductive protective grease, repaired the drain hose. Cleared fault codes; no recurrence.
BYD DTC AI Analysis

Loose connector after accident repair causes intermittent fault

✓
After repairing a right rear side collision on a Qin 100, the dashboard intermittently displayed an airbag fault. Testing revealed intermittent DTC B175B-00. Inspection found technicians had replaced the right rear side airbag during the accident repair, but the connector locking tab had not fully engaged. Vehicle vibration caused poor terminal contact, with resistance fluctuating between 0.5 and 2.0 Ω. After reseating the connector and confirming the locking tab clicked into place, the data stream showed stable resistance at 2.2 Ω and the fault resolved.
BYD DTC AI Analysis

Airbag module requires replacement due to internal igniter short circuit

✓
A 2018 Qin EV300 showed persistent DTC B175B-00. Disconnected the airbag module and connected a simulator to the harness; the DTC changed to open circuit (normal). Harness insulation to ground measured good. Measured the airbag module resistance separately: 0.2Ω, well below the 2.0Ω standard. Determined the airbag igniter was internally shorted. Replaced the right rear side airbag module (required new mounting bracket and bolts), performed system configuration write, and cleared the fault.
BYD DTC AI Analysis

Aftermarket seat heating pad installation pinched wiring harness

✓
A Qin 80 owner reported an illuminated airbag warning light after installing an aftermarket seat heater. Inspection found that while drilling into the right rear seat foam to route wiring, the installer used screws that were too long, piercing the harness sheath and shorting the airbag harness positive and negative leads. Replaced the damaged harness section (severe internal damage required replacing the entire section). Rerouted the wiring to avoid the heating elements. Fault resolved.
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.