AU
B175D

This fault code indicates the SRS (Supplemental Restraint System) control module detects a resistance of 0 Ω (or below 0 — Seal U

Safety System

This fault code indicates the SRS (Supplemental Restraint System) control module detects a resistance of 0 Ω (or below 0.5 Ω) in the Left Front Side Curtain Airbag squib circuit.

Under normal conditions, standard airbag squib resistance is 2.0 to 3.0 Ω (typical BYD specification is 1.5 to 4.0 Ω).

A 0 Ω resistance indicates a short circuit in the squib circuit.

Possible causes include a wiring harness short to ground, a wire-to-wire short (power wire shorted to ground wire), or an internal short in the squib bridge wire.

This fault causes the SRS control module to identify the airbag circuit as abnormal, illuminate the airbag warning light, and disable Left Front Side Curtain Airbag deployment.

In a collision, this side curtain airbag will fail to inflate and deploy, severely compromising side impact protection.

Additionally, the short circuit creates a potential risk of unintended airbag deployment.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Airbag igniter internal short circuit: The igniter bridge wire inside the left front side curtain airbag module melts and fuses due to a manufacturing defect, aging, or impact, causing direct continuity between the two terminals and a resistance of 0.
  • 2Harness short to ground: The harness from the SRS control unit to the left front side curtain airbag (usually routed along the left A-pillar, B-pillar, and C-pillar roof side rails) has damaged insulation and contacts the vehicle body metal frame, causing a short to ground.
  • 3Connector terminal short circuit: Water ingress, oxidation, corrosion, bent or deformed terminals, or metallic debris inside the wiring harness connector (located below the A-pillar or near the B-pillar, usually mating with the body harness) shorts the power terminal to the ground terminal.
  • 4SRS control unit internal sampling circuit fault: A damaged A/D converter, sampling resistor, or drive circuit inside the control unit causes the sampled resistance of the left curtain airbag circuit to constantly read 0, triggering a false fault.
  • 5Vehicle modification or repair damage: When routing dash cam wiring, removing the A-pillar trim panel, installing a roof rack, or replacing glass, screws or rivets pierce the wiring harness, or metal edges pinch the harness, damaging the insulation and causing a short circuit.
What To Do
  • 1
    Safety Preparation: Park the vehicle on level ground, apply the parking brake, turn the ignition switch to the OFF position, disconnect the 12V battery negative cable, and wait at least 90 seconds (to ensure the SRS backup power capacitor fully discharges, preventing accidental airbag deployment).
  • 2
    DTC Confirmation: Reconnect the battery, turn the ignition switch to the ON position, and use the BYD dedicated diagnostic tool (VDS2000 or VDS6000) to enter the SRS system. Read the fault codes to confirm B175D is a current fault (Active), and record the ambient temperature and vehicle status from the freeze frame data.
  • 3
    Visual inspection: Remove the upper trim panels from the left A-pillar, B-pillar, and C-pillar. Inspect the side curtain airbag wiring harness along the roof side rail for obvious damage, crushing, cuts, water stains, or burn marks. Focus on contact points between the wiring harness and the vehicle body metal.
  • 4
    Disconnected airbag measurement: Switch off the ignition, disconnect the battery negative terminal again, and wait 90 seconds. Disconnect the left front curtain airbag connector (usually located at the lower A-pillar or middle B-pillar; yellow connector with a shorting bar). Use a digital multimeter to measure the resistance between the two terminals on the airbag side (not the wiring harness side). Normal resistance is 2.0-3.0 Ω. If the resistance is 0 Ω or close to 0 Ω, the airbag module has an internal short circuit. Replace the left front curtain airbag assembly.
  • 5
    Harness continuity check: If the airbag resistance is normal, measure at the harness-side connector: ① Check for a short circuit between the two terminals (resistance should be infinite; continuity indicates a short between wires). ② Measure the resistance from each terminal to body ground (resistance should be infinite; continuity indicates a short to ground). Also check continuity between the harness and the SRS control unit.
  • 6
    Shorting bar check: Verify the shorting bar inside the airbag connector returns to its normal position. This device must automatically short the airbag terminals when disconnecting the plug. A stuck shorting bar may cause measurement errors or circuit faults.
  • 7
    Control unit inspection: If the wiring harness and airbag are normal, check the SRS control unit connector terminals for corrosion or pin push-back. Measure the circuit insulation between the control unit and the airbag. If necessary, use an oscilloscope to check the diagnostic pulse output from the control unit.
  • 8
    Repair and verification: After repairing or replacing the shorted wiring harness/airbag, reconnect all connectors (listen for an audible click), connect the battery, and clear the fault code. Perform an SRS system self-check cycle (turn the ignition switch ON; observe the airbag warning light illuminate for 6 seconds and then turn off). Use the diagnostic tool to read the data stream and confirm the left front side curtain airbag resistance returns to the normal range. Perform a road test to confirm the fault does not recur.
Real-World Cases
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BYD F3 ABS DTC C0032 (wheel speed sensor fault)

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Symptoms: At 8600 km, the ABS warning light came on and stayed on while driving (Delphi system). Diagnosis: 1. Connected diagnostic scan tool and retrieved DTC C0032 (left front wheel speed sensor open or short circuit). 2. Inspected wheel speed sensor wiring harness and found it had chafed through against the left front tire. Replaced the harness; fault remained. 3. Disconnected left front wheel speed sensor connector and measured resistance between terminals 1-A6 and 2-A6: 1750 Ω (specification 1780±150 Ω). Reading normal. 4. Checked driveshaft reluctor ring and found missing teeth. Solution: Replaced left front driveshaft assembly (including wheel speed sensor reluctor ring). Road tested; fault resolved.
Original source ↗
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BYD Qin/Tang High Voltage Interlock Loop Fault (BMS-Related)

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Symptoms: Vehicle unable to energise high voltage system. High voltage battery management system live data shows 'High Voltage Interlock: Locked', with high voltage contactors open. Diagnosis: 1. Read high voltage battery management system live data and confirmed abnormal high voltage interlock status. 2. Measured infinite resistance (no continuity) between pins K64-01 and K65-07 at the high voltage battery management system, confirming an open circuit in the interlock loop. 3. Sectional measurement between pins K54-02 and K54-06 at the high voltage distribution box showed normal continuity (resistance <1Ω), ruling out distribution box faults. 4. Service disconnect switch terminals K66-01 and K66-02 showed normal continuity, but inspection found a backed-out pin at the high voltage harness interlock connector between the drive motor controller and DC-DC converter assembly. Resolution: Reseated the high voltage harness interlock connector, ensuring pins fully inserted and locked. Fault resolved.
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BYD EPS Steering System Fault (Multiple Fault Codes Case)

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Symptoms: Dashboard displays "Check steering system" or the EPS warning light stays on. Power steering assist suddenly cuts out (heavy steering) or is intermittent. Some vehicles also have steering wheel binding or abnormal noise. Diagnosis: 1. Read OBD fault codes using a diagnostic tool (e.g., C1B0E00, C106600 and other steering-related codes); 2. Electronic check: Measure EPS control module supply voltage (CAN High + CAN Low standard value should be 5V), and check torque/steering angle sensor signals for distortion; 3. Mechanical check: Turn the steering wheel by hand to check for abnormal noise; raise the vehicle and inspect steering tie rods and ball joints for play; 4. Found: Some vehicles have EPS control module software faults or poor ground connections (loose connectors). Repair: 1. Recalibrate torque/steering angle sensors using dedicated equipment; 2. Inspect and repair wiring, sand ground points, and replace damaged or misaligned connectors; 3. Update EPS control module software; 4. For mechanical wear (e.g., steering gear wear, seal aging), replace the REPS assembly or worn components.
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BYD new energy vehicle air conditioning compressor failure (scroll plate sealing defect)

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Symptoms: Poor cooling performance; high low-side pressure, low high-side pressure, ice on the low-pressure line, and no cold air output. Diagnosis: 1. Verified no incorrect refrigerant had been added; connected manifold gauges and found abnormal pressures. 2. Removed the compressor rear cover. The scroll plate surfaces were abnormally smooth (no visible wear), but the scroll set lacked seal rings (design defect), causing internal leakage. 3. Confirmed abnormal wear—the surfaces should show irregular wear patterns but were mirror-smooth. Repair: 1. Replaced the scroll plate with the manufacturer-revised version featuring added seal rings. 2. Added EV-specific POE refrigeration oil. 3. Reinstalled the scroll plate to the original position and reassembled. After installation, the AC outlet temperature dropped to 4°C and cooling returned to normal.
Original source ↗
Other Seal U 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.