AU
B1705-00

This DTC indicates the Supplemental Restraint System (SRS) detects a short to ground in the left curtain airbag deployment circuit — Seal U

Safety System

This DTC indicates the Supplemental Restraint System (SRS) detects a short to ground in the left curtain airbag deployment circuit.

Specifically, during self-diagnostics or monitoring, the SRS control module (ACU) detects insulation resistance between the left curtain airbag igniter circuit and vehicle ground (GND) below the system threshold (typically <2Ω).

This causes abnormal current leakage to ground instead of normal flow through the airbag deployment circuit.

This fault may result in: 1) the left curtain airbag failing to deploy normally in a collision, compromising head protection for front and rear left occupants; 2) the SRS entering fail-safe mode, disabling related airbag functions, and illuminating the instrument cluster airbag warning light; 3) unintended airbag deployment in extreme cases due to abnormal circuit heating.

The fault involves the left curtain airbag module, wiring harness, connectors, or internal SRS control module circuits.

The B1705-00 fault code on the Seal U indicates a high-severity SRS fault: a short to ground in the left curtain airbag deployment circuit. This can stop the left curtain airbag deploying correctly and may trigger the airbag warning light or fail-safe mode. Common causes include damaged wiring in the pillar or roof area, or water ingress and corrosion at the connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Left curtain airbag wiring harness worn or pinched: Inside the A-pillar, B-pillar, or C-pillar trim panels, the wiring harness rubs against the body metal frame, seat mounting bracket, or roof reinforcement, damaging the insulation and causing the conductor to directly contact the body ground.
  • 2Connector water ingress or corrosion: Vehicle wading, a blocked sunroof drain tube, or poor body sealing causes water ingress into the left curtain airbag connector (usually located in the left body side panel, headliner, or C-pillar trim), creating a conductive path between the terminals or producing verdigris.
  • 3Curtain airbag module internal fault: Abnormal drop in inflator internal igniter resistance (below 1.0Ω) or internal short circuit, causing impedance to ground to fall outside standard specifications (standard value typically 2.0±0.1Ω).
  • 4SRS control module (ACU) internal driver circuit fault: Ignition driver transistor breakdown or monitoring circuit fault inside the control module causes a false short-circuit detection or an actual output short circuit.
  • 5Improper collision repair: During collision repair, a missing left curtain airbag wiring harness retaining clip, incorrect harness routing contacting sharp edges, or the use of a non-genuine specification connector resulting in poor sealing.
What To Do
  • 1
    Safety preparation and system discharge: Park the vehicle in a safe area, apply the parking brake, turn the ignition switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor and prevent accidental airbag deployment.
  • 2
    Fault Confirmation and Data Recording: Use the BYD VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B1705-00 is a Current fault, not a History fault. Record the Freeze Frame Data, including parameters such as vehicle speed and temperature at the time the fault occurred.
  • 3
    Visual inspection and wiring harness check: Remove the left A-pillar upper trim panel, B-pillar upper trim panel, left headliner trim panel, and C-pillar trim panel. Inspect the left curtain airbag wiring harness for wear, cuts, or burn marks. Verify the harness protective sleeve is intact near the seat rails, seat belt mounting points, and body sheet metal holes. Inspect the connectors for looseness, water ingress, corroded pins, or backed-out terminals.
  • 4
    Circuit test and isolation diagnosis: Disconnect the SRS control module and left side curtain airbag module connectors. Use a multimeter to measure the resistance between the harness-side connector ignition circuit terminal and body ground (standard value: >10MΩ), and measure continuity between the harness terminals (continuity must exist with resistance <1Ω). If the harness is normal, connect a 2Ω special resistor to the SRS control module in place of the curtain airbag module. If the fault code clears and does not return, the curtain airbag module is faulty.
  • 5
    Component replacement and repair: Based on diagnostic results, replace the left curtain airbag assembly (Note: The airbag module is a single-use component; if deployed or if resistance is abnormal, replace the complete unit. Do not repair the internal structure), repair the damaged wiring harness (wrap with waterproof insulating tape or replace the wiring harness assembly), or clean or replace corroded connectors.
  • 6
    System reset and function verification: Reconnect all connectors. Ensure the connectors lock fully and the waterproof seals seat correctly. Install all interior trim panels. Connect the battery negative terminal. Use the diagnostic tool to clear the fault code. Perform the SRS system self-check (usually requires cycling the ignition switch 3 times). Confirm B1705-00 does not recur. Check that the instrument panel airbag warning light turns off normally after the self-check (the light illuminating during the self-check and turning off after 6 seconds indicates normal operation).
Real-World Cases
BYD DTC AI Analysis

Song MAX driver seat backrest rearward adjustment inoperative

✓
Symptoms: The instrument cluster showed a seat adjustment system fault. The driver’s seat could not electrically adjust the backrest angle, the seat memory function failed, and the cluster displayed a “Check Seat System” warning. Diagnosis: The technician scanned with a VDS diagnostic tool and retrieved DTC B1705-00 (Driver Seat Back Rearward Adjustment Switch Circuit Fault). Inspected the under‑seat harness connector – secure, no looseness. Removed the seat side switch panel, measured resistance of the backrest rearward adjustment switch, and found an internal open circuit (normally should be closed). Checked the harness from the switch to the seat control module; continuity was normal, no shorts or opens. Solution: Replaced the driver seat switch assembly (includes backrest forward and rearward adjustment switches). Cleared the DTC and test‑drove the vehicle. All electric seat adjustment functions returned to normal and the DTC did not return. Note: On Song MAX models, DTC B1705‑00 indicates a seat switch circuit fault.
Original source ↗
BYD DTC AI Analysis

Qin Pro DM seat back rearward adjustment intermittently inoperative

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Symptoms: BYD Qin Pro DM. The owner reported the driver's seat backrest adjustment button was inoperative; there was no response when adjusting rearward, while forward adjustment worked normally. After powering on the vehicle, the instrument cluster occasionally displayed a seat system fault warning. Diagnosis: At the shop, technicians used the BYD dedicated diagnostic tool to retrieve fault codes, which showed B1705-00 (driver's seat backrest rearward switch circuit fault). They removed the seat side trim panel and inspected the switch connector, finding no oxidation or corrosion. Using a multimeter on the switch signal wire, they detected no voltage change when pressing the rearward adjustment switch (normally a 12V or 5V signal change should occur). They further disassembled the switch and found burned internal contacts and poor connection. Solution: Since the individual switch component was unavailable, technicians replaced the entire seat adjustment switch panel assembly and re-matched the seat memory function, resolving the fault. After clearing the B1705-00 fault code, it did not return. This fault code is related to the seat system in the Qin Pro DM.
Original source ↗
BYD DTC AI Analysis

Tang petrol: Seat backrest rearward adjustment inoperative, accompanied by abnormal relay noise

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Symptoms: BYD Tang petrol variant, 32,000 km. The driver reported the power seat backrest adjustment failed — it moved forward but not backward. When using the switch, a relay clicked but the motor did not run. Diagnosis: Scanned with a Launch X431 and retrieved DTC B1705-00 from either the Body Control Module (BCM) or seat control module. The technician first suspected a defective motor or mechanical binding. Powered the backrest adjustment motor directly and it ran normally. Checked the switch signal and found the rearward adjustment signal did not reach the control module. Tested the switch itself and found oxidised internal contacts interrupting the signal. Resolution: Cleaning the switch contacts was ineffective. Replaced the driver's seat eight-way adjustment switch assembly. Cleared the fault code. The seat backrest now adjusts in both directions. A three-month follow-up confirmed no recurrence.
Original source ↗
BYD DTC AI Analysis

Han EV Genesis Edition seat adjustment fault related to temperature and humidity

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Symptoms: BYD Han EV Founders Edition. After 6 months from new, the driver's seat backrest rearward adjustment began to fail intermittently. The fault occurred more frequently in hot weather and occasionally worked normally when cold. Diagnostic process: The dealership technician received the vehicle and confirmed the fault after multiple test drives. VDS scan retrieved historic DTC B1705-00. Inspected the seat wiring harness routing and identified a risk of interference and chafing near the seat rails. Removed and inspected the switch; found slight moisture traces on the internal PCB, suspected to be related to HVAC condensation or humid conditions. Measured the switch insulation resistance, which was below specification. Solution: Replaced the seat adjustment switch assembly. Fitted protective sleeving to the wiring harness at wear-prone areas and adjusted the routing to prevent interference with moving components. Fault eliminated after the repair.
Original source ↗
BYD DTC AI Analysis

Atto 3 seatback adjustment failed after an aftermarket seat ventilation installation.

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Symptoms: BYD Yuan Plus. After the owner modified the seat ventilation, the driver’s seat backrest rearward adjustment failed, though other directions worked normally. The instrument cluster showed no warning lights, but the seat memory function could not save positions. Diagnosis: The workshop first scanned the vehicle with a diagnostic tool and found DTC B1705-00 stored in the seat control module. The shop asked the owner and learned the seat had been removed during the modification. Inspecting the switch plug revealed that while drilling holes for the ventilation fan, the technician had accidentally damaged the wiring harness for the backrest rearward adjustment switch with the drill bit. This caused the signal wire to break internally while the insulation remained visually intact. Solution: Repaired the damaged wiring harness (reconnected the broken signal wire and applied insulation and waterproofing). After clearing the fault codes, all seat functions returned to normal. Advised the owner to choose a professional workshop for future seat modifications.
Original source ↗
Other Seal U Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.