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B110C09

DTC B110C09 indicates a driver-side seat belt pretensioner circuit fault, specifically an open circuit, short to ground, or abnormal resistance (standard resistance 1 — Atto 3

Thermal Management System

DTC B110C09 indicates a driver-side seat belt pretensioner circuit fault, specifically an open circuit, short to ground, or abnormal resistance (standard resistance 1.8-2.5Ω).

This fault relates to the Supplemental Restraint System (SRS).

The Airbag Control Unit (ACU) triggers this code upon detecting driver-side pretensioner circuit voltage or resistance outside the specified threshold.

The pretensioner is a critical safety device operating in conjunction with the airbag.

During a collision, the gas generator tightens the seat belt to eliminate slack between the webbing and the occupant.

This fault forces the airbag system into fail-safe mode and continuously illuminates the instrument panel airbag warning light.

This condition can prevent the pretensioner from deploying during a collision, significantly increasing occupant injury risk.

8
Cases Logged
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro DM - Loose seat belt pretensioner connector

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Symptoms: Dashboard airbag warning light stays on after starting. DTC B110C09 (driver side seatbelt pretensioner open circuit). Diagnosis: Inspected wiring harness connector under driver's seat – found loose with slightly oxidised pins. Pretensioner resistance measured 2.1Ω (normal). Determined intermittent open circuit caused by poor connector contact. Repair: Cleaned connector pins and applied conductive grease. Reconnected firmly and secured harness with cable tie near seat rail to prevent pulling when seat moves. Cleared DTC, test drove vehicle – airbag light went out.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song PLUS DM-i - Seatbelt buckle switch internal fault

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Symptoms: While driving, the instrument cluster occasionally displayed "Check Airbag System." DTC B110C09 appeared intermittently, easily triggered on rough roads or after adjusting the seat angle. Diagnosis: Connected a diagnostic tool and monitored live data. Found the driver seatbelt buckle switch signal flickering between fastened and unfastened. Removed the buckle assembly and found the internal micro-switch contacts were burnt. Wiring harness voltage measured 12V, within normal range. Fix: Replaced the driver-side seatbelt buckle assembly (part number: SCE-5813100). Recalibrated the seatbelt status, cleared DTCs, and road tested. The signal remained stable.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM accident-repaired vehicle - seatbelt pretensioners deployed but not replaced

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Symptom: After front collision repairs, the dashboard continuously displays an airbag fault. DTC B11009C (driver seat belt pretensioner circuit fault). Diagnosis: Reviewed repair records and found the driver pretensioner had deployed (locked) during the frontal impact, but the shop only performed a visual inspection without replacing the unit. Disassembled the component and found the pretensioner internally disconnected with infinite resistance. Solution: Replaced the driver side seat belt assembly (with pretensioner, part number: EM2E-5813100). Connected a diagnostic tool to write the airbag system configuration and match the coding. Cleared the crash records and fault codes, then completed the self-test.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Dolphin - Worn seat wiring harness causes intermittent open circuit

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Symptoms: At 8,000 km, the airbag warning light illuminated intermittently. DTC B110C09 set intermittently. The fault occurred mainly when adjusting the seat to full forward or rearward positions, and disappeared when the seat was centred. Diagnosis: Repeated seat adjustment testing revealed a design defect in the wiring harness protective sleeve between the floor pan and seat frame. Long-term friction had damaged the insulation on the pretensioner signal wire (yellow/black), causing a short to ground at specific seat positions. Resolution: Repaired the damaged harness, re-wrapped it with insulation tape, added corrugated conduit, and adjusted the harness routing. Added rubber grommets and harness clips at the seat rail mounting points. Cleared the DTC and performed 20 full-range seat adjustment cycles to confirm the fault was eliminated.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro DM - Loose seat belt pretensioner connector

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Symptoms: Dashboard airbag warning light stays on after starting. DTC B110C09 (driver's side seat belt pretensioner open circuit). Diagnosis: Found the wiring harness connector under the driver's seat loose, with slightly oxidised pins. Measured pretensioner resistance at 2.1Ω (normal). Determined that poor connector contact caused an intermittent open circuit. Repair: Cleaned the connector pins and applied conductive grease. Reconnected firmly and secured the harness near the seat rail with a cable tie to prevent pulling when the seat moves. Cleared the DTC and test-drove the vehicle – airbag light went out.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song PLUS DM-i - Seatbelt buckle switch internal fault

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Symptoms: The dashboard occasionally displayed "Check Airbag System" while driving. DTC B110C09 appeared intermittently, particularly on rough roads or when adjusting the seat angle. Diagnosis: Connected a scan tool and monitored live data. Found the driver's seat belt buckle switch signal toggling between fastened and unfastened. Removed the buckle assembly and found burnt contacts on the internal micro-switch. Wiring harness voltage was normal at 12V. Fix: Replaced the driver-side seat belt buckle assembly (part number: SCE-5813100). Recalibrated the seat belt status, cleared the DTC, and road tested. The signal remained stable.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM accident-repaired vehicle - seatbelt pretensioners deployed but not replaced

✓
Symptoms: After front collision repairs, the instrument cluster continuously displayed an airbag fault, DTC B110C09 (driver seatbelt pretensioner circuit fault). Diagnosis: Repair history review found the driver pretensioner had deployed (locked) during the frontal impact, but it had only been visually inspected, not replaced. Disassembly revealed the pretensioner was internally disconnected with infinite resistance. Solution: Replaced the driver-side seatbelt assembly (with pretensioner, part number: EM2E-5813100), connected the diagnostic tool to write the airbag system configuration and perform coding match, cleared crash records and fault codes, and completed the self-test.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Dolphin - Worn seat wiring harness causes intermittent open circuit

✓
Symptoms: At 8,000 km, the airbag warning light on the instrument cluster illuminated intermittently. DTC B110C09 appeared intermittently, mainly when adjusting the seat to the full forward or rearward positions, and disappeared when centred. Diagnosis: Repeated seat adjustment testing revealed a design defect in the wiring harness protective sheath between the floor pan and seat frame. Long-term friction damaged the insulation on the pretensioner signal wire (yellow/black), causing a short to ground at specific seat positions. Resolution: Repaired the damaged harness, rewrapped it with insulation tape and added corrugated tubing, and adjusted the harness routing. Added rubber grommets and harness clips at the seat rail mounting points. Cleared the DTC and performed 20 full-range seat adjustment cycles to confirm the fault was resolved.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.