AU
B175C1B

DTC B175C1B indicates the SRS (Supplemental Restraint System) detects the right rear side airbag ignition circuit resistance exceeds the normal upper limit (typically > 10Ω; standard value 2 — Qin Plus

Safety System

DTC B175C1B indicates the SRS (Supplemental Restraint System) detects the right rear side airbag ignition circuit resistance exceeds the normal upper limit (typically > 10Ω; standard value 2.0-5.0Ω).

This fault represents a high-resistance or open-circuit condition in the airbag ignition circuit.

During a collision, the airbag control unit (ACU) may fail to supply sufficient current to ignite the gas generator.

Consequently, the right rear side airbag will not deploy properly, severely compromising occupant side-impact protection.

The manufacturer-specific '1B' sub-code typically indicates high resistance or an intermittent circuit.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Poor contact at airbag wiring harness plug: Long-term vibration, oxidation, or water ingress increases terminal contact resistance at the right rear side airbag connector (usually located inside the C-pillar trim panel or under the seat).
  • 2Wiring harness wear or open circuit: Forward and backward seat movement mechanically wears the wiring harness between the seat frame and the body, breaking the internal copper strands without complete separation (high-resistance state).
  • 3Airbag module internal fault: An open circuit or poor connection in the gas generator igniter coil causes abnormally high circuit resistance.
  • 4ECU detection circuit fault: A faulty sampling resistor or detection chip inside the airbag control unit for the right rear side airbag generates a false alarm.
  • 5Improper modification or repair: Failing to correctly reconnect the airbag connector during rear C-pillar trim panel removal and installation, or accidentally damaging the wiring harness when installing seat covers.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to allow the airbag system to fully discharge. Use a multimeter to confirm the system has no voltage.
  • 2
    Fault confirmation: Connect the VDS2000/Launch X431 diagnostic tool, read and record the DTC B175C1B status (current/history), and check the 'right rear side airbag resistance' value in the data stream (usually reads above 10Ω or open circuit).
  • 3
    Visual inspection: Remove the right rear C-pillar trim panel and rear seat side trim panel. Verify the airbag wiring harness connector (yellow connector) is fully locked. Inspect the terminals for oxidation, corrosion, or backed-out pins.
  • 4
    Resistance measurement: Use a multimeter to measure the resistance at the airbag connector (disconnect the ECU side and measure the airbag side). Standard resistance is 2.0-5.0Ω. If the resistance is infinite or >10Ω, replace the airbag assembly. If normal, check the wiring harness.
  • 5
    Harness continuity test: Measure wiring harness continuity between the airbag connector and the SRS ECU. Closely inspect the harness sleeve in the seat movement area. Repair open circuits or high-resistance sections, or replace the wiring harness assembly if necessary.
  • 6
    Replacement verification: If the wiring harness and connector are normal, test with a known-good airbag to confirm if the fault transfers and determine if the ECU has an internal fault.
  • 7
    Repair and Reset: After completing the repair, reconnect all connectors, install the trim panels, and connect the battery. Use the diagnostic tool to clear the fault code. Execute 'Airbag System Configuration Write' and 'Sensor Calibration' (if required). Finally, perform a road test to confirm.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: Oxidized right rear C-pillar connector caused high resistance

✓
Vehicle: 2018 Qin PRO DM, 42,000 km. Fault symptom: Dashboard airbag warning light steady on. VDS read DTC B175C1B (right rear side airbag resistance too high). Live data showed 12.8 Ω resistance (specification 2.0–5.0 Ω). Diagnosis: Removed right rear C-pillar trim and inspected the side airbag harness connector (yellow double-lock). Found slight internal oxidation and the connector was inserted but not fully locked, causing high contact resistance at the terminals. Cleaned the terminals with electronic contact cleaner, applied conductive paste, and secured the connector lock. Resistance measured 3.2 Ω after repair. Cleared the DTC and road-tested 50 km with no recurrence.
BYD DTC AI Analysis

Qin PRO Fuel: Seat wiring harness wear causing intermittent warning

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Vehicle: 2019 Qin Pro petrol, 68,000 km. Symptom: Airbag warning light illuminating intermittently, particularly on rough roads. Scan tool retrieved historical DTC B175C1B. Diagnosis: Inspected the C-pillar connector and measured airbag resistance (both normal). Further inspection revealed the wiring harness sheath between the right rear seat frame and body sill had worn through and split. Inside, two copper conductors were mostly fractured, with only a few strands remaining, creating a high-resistance condition. Root cause: Repeated harness flexing from long-term seat adjustment and passengers entering/exiting the rear seats. Repair: Cut out the damaged harness section and soldered in replacement heat-resistant cable of identical specification (0.5mm² twisted shielded pair). Rerouted the harness and fitted additional abrasion-resistant sleeving. Fault completely resolved.
BYD DTC AI Analysis

BYD Qin PRO DM Airbag Assembly Internal Open Circuit Replacement Case

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Vehicle: 2019 BYD Qin Pro DM. Fault appeared following accident repairs. Symptom: Instrument cluster displayed airbag warning after repairs. Retrieved DTC B175C1B, would not clear. Diagnosis: Inspected related connectors and harness – no abnormalities found. Measured continuity from ECU to connector: normal, resistance <1Ω. Disconnected airbag connector and directly jumpered the plug terminals. Scan tool showed resistance returned to normal (2.1Ω), confirming airbag unit failure. Disassembled the airbag and found the internal igniter lead had detached at the solder joint from accident impact, causing high resistance. Repair: Replaced right rear side airbag assembly (part number: XKXXX-XXXXX), performed ECU configuration coding and system self-test. Fault resolved.
BYD DTC AI Analysis

False airbag control unit fault in flood-damaged vehicle

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Vehicle: 2018 BYD Qin PRO petrol. History of right rear carpet water damage from blocked sunroof drain tubes. Symptom: Airbag warning light on; DTC B175C1B. Diagnosis: Airbag and wiring harness resistance checked normal; no connector oxidation. Found water staining on the SRS control unit mounting bracket (under the centre console). Pins 18 and 19 on the control unit connector (right rear side airbag circuit) were slightly corroded. Water ingress caused abnormal reference voltage in the ECU internal detection circuit, falsely indicating high airbag resistance. Repair: Thoroughly cleaned the control unit connector with alcohol, dried it, and applied insulating silicone grease. Cleared the fault code; no recurrence.
Other Qin Plus 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.