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B1782

DTC B1782 indicates the SRS (Supplemental Restraint System) control unit detects a short-to-ground fault in the right middle-row seat belt pretensioner circuit — Atto 3

Safety System

DTC B1782 indicates the SRS (Supplemental Restraint System) control unit detects a short-to-ground fault in the right middle-row seat belt pretensioner circuit.

Specifically, the resistance between the pretensioner squib positive or negative circuit and body ground falls below the system threshold (typically < 1Ω), causing the ECU to flag a circuit fault.

This fault forces the SRS into a degraded protection mode, disables the right middle-row and associated airbag and pretensioner functions, and continuously illuminates the airbag warning light on the instrument cluster.

During a collision, the pretensioner may fail to deploy and tighten the seat belt.

This significantly reduces occupant protection and constitutes a severe driving safety fault.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song MAX second-row seat rails chafed through wiring harness, causing intermittent short circuit

✓
A 2019 Song MAX stored DTC B1782 intermittently. Inspection found the right middle-row seat uses an independent sliding design; the sharp rear edge of the seat runner wore through the pretensioner wiring harness sheath, causing the copper wires to occasionally contact the seat frame. Repaired the harness, rewrapped it with high-temperature resistant corrugated tubing, repositioned the clips to avoid runner interference, and eliminated the fault.
BYD DTC AI Analysis

Tang DM SRS connector corroded and shorted after wading

✓
2021 Tang DM showed an airbag warning on the instrument cluster after driving through floodwater. Scan tool read DTCs B1782 and B1781 (second row left). Disassembly revealed the carpet beneath the second row seats saturated, with green corrosion on the terminals inside two yellow SRS connectors causing a short to ground. Cleaned the connectors with electronic cleaner, blow-dried them, and applied conductive protectant. Replaced the carpet waterproof underlay and cleared the fault codes. System returned to normal.
BYD DTC AI Analysis

Yuan EV Seatbelt Pretensioner Internal Igniter Short Circuit Replacement Case

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A 2019 Yuan EV set DTC B1782 after accident repairs. Wiring harness checked normal. With the pretensioner connector disconnected, resistance between the pretensioner body terminals and casing measured 0.3Ω (should be infinite), confirming internal moisture had caused a short. Replaced the right middle row seat belt retractor assembly (P/N: 6A-8217060), cleared the code, and the SRS system passed self-test. After replacement, run 'configuration coding write' in the diagnostic tool to match the new component parameters.
BYD DTC AI Analysis

Improperly secured wiring harness after Qin Pro accident repair

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2020 BYD Qin petrol: After collision repair, the customer reported the airbag warning light on. Scan revealed DTC B1782. Reviewing the repair history showed the right rear seat pretensioner harness had been pinched by a seat mounting bolt during reinstallation, damaging the insulation and shorting to earth. Rerouted the harness, fitted a protective sleeve and replaced the damaged section. Fault resolved. After body repairs involving SRS components, verify harness routing against the factory wiring diagram.
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.