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B1705-00

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

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.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song MAX driver seat backrest rearward adjustment inoperative

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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.
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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.
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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.
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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.
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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.
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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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.