AU
B175F

DTC B175F indicates the SRS (Supplemental Restraint System) control unit detects the left front curtain airbag (CAB) ignition circuit resistance falls outside the normal range (normal value: 2 — Qin Plus

Safety System

DTC B175F indicates the SRS (Supplemental Restraint System) control unit detects the left front curtain airbag (CAB) ignition circuit resistance falls outside the normal range (normal value: 2.0–3.0 Ω; fault threshold: >6 Ω or open circuit).

This Level 2 airbag system fault means the affected curtain airbag may fail to deploy or deploy late during a collision, severely compromising occupant side-impact protection.

The SRS ECU continuously monitors each airbag inflator circuit resistance using a Wheatstone bridge.

Excessive resistance typically indicates poor circuit contact, high wiring impedance, or an open circuit within the inflator.

On BYD new energy vehicles, check for potential electromagnetic interference from the high-voltage interlock circuit affecting the SRS.

The B175F fault code on the Qin Plus indicates a medium-severity SRS fault in the left front curtain airbag ignition circuit, where resistance is too high or the circuit is open. This may stop the curtain airbag from deploying correctly in a side impact. Common causes include corroded or loose airbag connectors and damaged wiring in the roof side rail. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Poor contact, oxidation, or corrosion at the left front curtain airbag connector (especially the dedicated yellow connector near the B-pillar and C-pillar, where prolonged moisture exposure causes terminal oxidation)
  • 2Airbag wiring harness worn or partially broken (frequent door cycling causes fatigue breakage in the wiring harness inside the roof side rail at the hinge, creating a high-resistance connection).
  • 3Internal open circuit in the clock spring (Spiral Cable) (poor contact in the internal flat ribbon cable if the curtain airbag circuit on this model routes through the clock spring under the steering wheel).
  • 4Open circuit due to aged airbag module internal squib (broken bridge wire inside gas generator or cold solder joint)
  • 5SRS control unit internal sampling circuit fault (drift in the ECU internal A/D converter or reference resistor causes a false high resistance reading)
What To Do
  • 1
    Safety Preparation: Disconnect the low-voltage battery negative terminal and wait at least 3 minutes to fully discharge the SRS backup capacitor. Wear an anti-static wrist strap. Disable the high-voltage system (perform the high-voltage power-down procedure for new energy vehicles).
  • 2
    Visual inspection: Check the left front side curtain airbag module connector (usually located inside the A-pillar/B-pillar trim panel) for looseness, water ingress, or corrosion. Check the wiring harness at the door hinge for wear or pinch marks.
  • 3
    Circuit resistance measurement: Disconnect the airbag module connector. Measure the wiring harness side resistance using a dedicated airbag tester or high-precision multimeter (test current <1mA). Normal resistance is <1Ω. If resistance is too high, measure in sections to locate the high-resistance point.
  • 4
    Airbag module isolation test: Connect a 2.7Ω dedicated simulation resistor to the circuit in place of the airbag module. If the fault code clears and the resistance is normal, the airbag module is faulty. If the fault persists, continue troubleshooting the wiring harness.
  • 5
    Clock spring inspection (if applicable): If this circuit passes through the steering wheel, inspect the clock spring connector, measure its continuity, and replace if necessary.
  • 6
    SRS ECU inspection: If the wiring harness and airbag are normal, check the SRS control unit power supply, ground, and internal faults. Reprogram or replace the SRS ECU if necessary.
  • 7
    Repair and verification: After repairing the wiring harness or replacing the faulty component, reconnect the battery. Use the BYD dedicated diagnostic tool to clear the fault code. Perform an SRS system self-check and confirm B175F does not return and the system status displays normal.
Real-World Cases
BYD DTC AI Analysis

Song MAX B-pillar connector water ingress and oxidation caused high resistance.

✓
A 2019 Song MAX frequently set DTC B175F with intermittent airbag warning light during the rainy season. Inspection found obvious water stains inside the left front side curtain airbag B-pillar connector, with terminals oxidised and black. Aged door seals let rainwater in, causing the connector's waterproof seal to fail. The technician cleaned the terminals, applied conductive protectant, and replaced the waterproof seal to clear the fault.
BYD DTC AI Analysis

Qin Pro roof wiring harness fractured internally at hinge

✓
2020 BYD Qin Pro set B175F at 80,000 km. Airbag module resistance measured normal, but harness circuit resistance was intermittent. Removed the headliner and found the wiring at the left front door upper hinge had fractured internal copper strands from long-term flexing, leaving only partial continuity and creating high resistance. Replaced the damaged harness section, added abrasion protection sleeves, and re-routed the harness to avoid excessive flexing.
BYD DTC AI Analysis

Open circuit in internal squib of side curtain airbag module due to aging

✓
A 2019 Song MAX set DTC B175F after collision repairs. Inspection revealed the left front side curtain airbag had partially deployed but was reset without replacement. Disassembling the module showed infinite resistance at the igniter—the internal bridge wire had broken. We installed a new left front side curtain airbag and performed configuration programming via the diagnostic tool (entering the new airbag serial number). The fault code cleared and the system passed self-test.
BYD DTC AI Analysis

SRS control unit sampling circuit false positive

✓
A Qin gasoline variant still showed DTC B175F after multiple airbag and wiring harness replacements. Oscilloscope testing of the SRS ECU sample voltage waveform revealed abnormal spike interference. Inspection found an aftermarket dashcam installed; its power line was interfering with the SRS system. Removing the device and checking the SRS ECU ground wiring revealed a loose ground point causing reference voltage drift. Tightening the ground point cleared the fault.
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus overview →
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.