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B175B1A

DTC B175B1A indicates the right rear side airbag igniter circuit resistance falls below the normal ECU threshold (typically below 1 — Qin Plus

Safety System

DTC B175B1A indicates the right rear side airbag igniter circuit resistance falls below the normal ECU threshold (typically below 1.0 Ω).

In the BYD SRS (Supplemental Restraint System), standard airbag igniter resistance is generally 2.0–3.0 Ω.

If the ECU continuously detects abnormally low circuit resistance, it logs a short circuit fault (indicating a possible short to ground or internal igniter short circuit).

This fault causes the following: 1) The airbag may fail to deploy during a collision, resulting in a loss of side protection. 2) The airbag may deploy unexpectedly in extreme cases. 3) The SRS enters fail-safe mode and illuminates the airbag warning light.

Common causes include wiring harness wear, connector water ingress, or an internal airbag module short circuit.

2
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Right rear side airbag module internal igniter short circuit (internal bridge wire short circuit or moisture ingress)
  • 2Wiring harness wear causing a short to ground (commonly due to a pinched or worn harness near the seat rail or inside the C-pillar trim)
  • 3Water ingress into the connector or terminal corrosion (vehicle wading, water entering the rear floor, or moisture entering the connector after a car wash)
  • 4SRS control unit internal detection circuit fault (faulty ECU sampling resistor or detection chip)
  • 5Wiring harness damaged during modification or repair (e.g., piercing the harness when installing seat heaters or retrofitting leather seats)
What To Do
  • 1
    Use the BYD VDS diagnostic tool to read fault codes, confirm B175B1A is a Current fault, record freeze frame data, and check for accompanying SRS fault codes (e.g., B175C).
  • 2
    Perform the safe power-off procedure: Disconnect the battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 3
    Inspect the right rear side airbag wiring harness connector (usually located below the C-pillar or on the side of the rear seat) for looseness, backed-out pins, signs of water ingress, or white corrosion. Clean and apply conductive grease if necessary.
  • 4
    Disconnect the SRS ECU connector (located under the center console or in the front compartment) and use a multimeter to measure the resistance at the right rear side airbag wiring harness terminal. Normal resistance is 2-3 Ω. A reading close to 0 Ω or <1 Ω confirms a wiring short circuit.
  • 5
    Check the wiring harness in sections: disconnect and measure from the ECU to the airbag. Inspect the harness for wear, damaged insulation, crushing, or deformation, focusing on the seat rail mounting points, inside the B-pillar trim panel, and inside the C-pillar trim panel.
  • 6
    Remove the right rear side airbag module (requires removing the C-pillar trim panel or seat backrest). Directly measure the resistance across the two terminals of the airbag module. If the resistance is <1Ω, replace the airbag module.
  • 7
    Repair the short circuit (wrap the wiring harness, replace the connector) or replace the faulty airbag module. Secure all connections to prevent poor contact.
  • 8
    Reconnect the battery, clear the fault code, and perform the SRS system self-check (turn the ignition switch to ON and observe if the airbag warning light turns off after 6 seconds). Perform a road test to verify.
Real-World Cases
BYD DTC AI Analysis

Steering wheel cruise control switch failure (B17 series reference)

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Symptoms: Steering wheel cruise control switch completely inoperative. Pressing the 'Set' button gets no response, and the instrument cluster shows no cruise setting information. Some owners reported abnormal instrument cluster warnings. Diagnosis: The owner replaced the steering wheel cruise control switch assembly, instrument panel relay assembly, and instrument cluster assembly one by one, but the fault remained. Technicians suspected either a faulty Set button or an internal break in the steering wheel clock spring wiring, blocking the switch signal from reaching the BCM. Solution: The forum post did not record a final confirmed solution. Follow-up posts suggested checking the steering wheel clock spring ribbon cable, multifunction switch connectors, and Body Control Module (BCM) software version. Note: Although this is not a direct B175B1A case, it demonstrates the wiring troubleshooting approach for B17-series fault codes.
Original source ↗
BYD DTC AI Analysis

VCU communication interrupted (pin backed out)

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**Symptoms:** Scan tool cannot communicate with the Vehicle Control Unit (VBU/VCU). Some electronic functions failed and the instrument cluster may display "Check Power System" or related warning lights. **Diagnosis:** Technician checked power, ground and CAN bus communication. Found pins G09-14/15 (GJK14 harness junction) backed out, breaking the communication signal. Confirmed fuse F4/9 had not blown, ruling out power supply problems. **Repair:** Fixed the backed-out pins in the wiring harness connector and re-secured the terminals for proper contact. Cleared DTCs with the scan tool. VCU communication returned to normal. **Note:** This case shows a system failure caused by wiring harness connector pin retraction in BYD vehicles. Useful reference for troubleshooting poor harness connections in SRS systems.
Original source ↗
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.