AU
B175B

DTC B175B indicates the Airbag Control Unit (ACU) detects the igniter (squib) circuit resistance for the right rear side airbag (typically the right C-pillar curtain airbag or right rear seat side airbag) falls below the system threshold (generally <1 — Atto 3

Safety System

DTC B175B indicates the Airbag Control Unit (ACU) detects the igniter (squib) circuit resistance for the right rear side airbag (typically the right C-pillar curtain airbag or right rear seat side airbag) falls below the system threshold (generally <1.5 Ω).

Normal airbag igniter resistance is 2.0-3.0 Ω.

Low resistance indicates a circuit short to ground, a wire-to-wire short, or an internal short within the airbag module igniter.

The ACU consequently registers the airbag as deployed or the circuit as faulty, disabling the airbag deployment function.

During a side impact, the right rear side airbag fails to inflate and protect the occupant.

This condition may trigger a continuous airbag warning lamp and constitutes a critical fault compromising passive safety.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Wear or crushing of the right rear side airbag wiring harness damages the insulation, causing a short to ground (commonly due to improper C-pillar trim panel removal/installation or the seat slide rail pinching the wiring).
  • 2Water ingress, oxidation, or deformed pins in the airbag wiring harness connector (usually located inside the right rear door sill trim panel or below the C-pillar), causing a short circuit between terminals.
  • 3Airbag gas generator (igniter) internal short circuit failure, resistance permanently low.
  • 4Airbag Control Unit (ACU) internal sampling circuit fault or software false detection
  • 5Poor sealing of the wiring harness connector in the right rear area allows moisture intrusion after vehicle wading or deep interior cleaning.
What To Do
  • 1
    Use the BYD VDS2000 or ED400 diagnostic tool to read the fault code, confirm B175B is active, record the freeze frame data, and check the specific resistance value in the data stream (usually <1.0Ω).
  • 2
    Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 3
    Remove the right C-pillar trim panel or right rear seat (depending on vehicle configuration). Locate the right rear side airbag wiring harness connector (black or yellow dedicated plug). Inspect the connector for water ingress, corrosion, or looseness.
  • 4
    Disconnect the airbag module connector and use a dedicated airbag resistance tester (or connect a 2.7Ω safety resistor in series) to measure the airbag assembly resistance. If the resistance is <1.5Ω, the airbag assembly has an internal short circuit. Replace the airbag module.
  • 5
    If the airbag unit is normal, use a multimeter to measure the resistance between the harness-side connector and body ground; it must be infinite. If continuity exists, inspect the harness along its routing for wear points. Focus on movement interference areas where the harness passes door seals and seat mounting brackets.
  • 6
    Check the Airbag Control Unit (ACU) terminal pins for bending or backing out. Measure continuity from the wiring harness end to the ACU end. Resistance should be <1Ω.
  • 7
    Repair damaged wiring harness sections (use heat-shrink tubing or replace the harness), treat connectors with water ingress (clean, blow dry, apply conductive grease), and replace the entire airbag wiring harness if necessary.
  • 8
    Reconnect all connectors and fully engage the locking tabs. Reconnect the battery, clear the fault code using the diagnostic tool, run the 'SRS System Self-Test' function, and confirm B175B does not reappear.
  • 9
    Perform a road test to simulate vehicle jolting and observe if the fault recurs. Finally, use the diagnostic tool to view the data stream and confirm the right rear side airbag resistance returns to the normal range of 2.0-3.0Ω.
Real-World Cases
BYD DTC AI Analysis

Seat mounting bolt crushed right rear curtain airbag wiring harness on Song MAX, causing short circuit

✓
A 2019 BYD Song MAX with 30,000 km arrived with the airbag warning light on. Scanning retrieved DTC B175B. Removing the right rear C-pillar trim revealed the side curtain airbag harness routed incorrectly at the seat mounting bracket; the seat mounting bolt had compressed the wiring over time, damaging the insulation and exposing the copper to the body ground. Repair: Cut out the damaged section, soldered in an extension wire, and sealed it with double-walled heat-shrink tubing. Rerouted the harness to clear the interference point. Fault resolved.
BYD DTC AI Analysis

Tang DM right rear airbag connector corrosion due to water ingress after wading

✓
2021 Tang DM. Airbag warning light appeared the day after driving through floodwater. Scanner showed active fault code B175B. Inspected the airbag connector inside the right rear sill trim panel and found the seal had deteriorated. Water ingress during wading caused terminal oxidation with green copper corrosion, creating a short between the pins. Replaced the airbag wiring harness connector (with waterproof seal), cleaned the airbag module terminals, and applied waterproof silicone grease to the connection. Fault resolved.
BYD DTC AI Analysis

Abnormal airbag resistance after accident repair on Yuan EV

✓
2019 BYD Yuan EV, right rear side collision. After an external workshop replaced the right rear side airbag, the instrument cluster displayed an airbag warning and set DTC B175B. Inspection revealed the technician had installed an aftermarket airbag assembly with an igniter resistance of only 0.8Ω, below the BYD ACU recognition threshold. Replaced the assembly with a genuine BYD right rear side airbag (part number must match VIN), executed 'Configuration Code Write' and 'Airbag Deployment Verification' using a diagnostic tool, and cleared the fault code.
BYD DTC AI Analysis

BYD Qin Pro: Frequent right rear seat adjustment caused wiring harness fatigue fracture and short circuit

✓
2020 Qin petrol variant. The right rear seat has a 60/40 split-fold design; the owner frequently folded the seat to transport cargo. Long-term flexing caused the airbag wiring harness inside the seat to fatigue and fracture. The exposed copper wires at the break splayed out and contacted the seat frame, shorting the circuit and setting DTC B175B. Repair action: Replaced the right rear seat airbag wiring harness assembly (including protective convoluted tubing). Added wiring harness retaining clips at the flex point to limit movement. Instructed the owner on proper use of the seat folding function.
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.