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B1727-00

This DTC indicates the Airbag Control Unit (ACU) detects the right knee airbag (front passenger knee airbag) squib circuit resistance is below the system calibration threshold (typically <1 — Atto 3

Safety System

This DTC indicates the Airbag Control Unit (ACU) detects the right knee airbag (front passenger knee airbag) squib circuit resistance is below the system calibration threshold (typically <1.0Ω; normal range: 2.0-3.0Ω).

Low resistance indicates an abnormally low-resistance path in the circuit.

A short to ground, a wire-to-wire short, or an internal short in the airbag squib typically causes this condition.

This fault presents two severe risks: first, short-circuit current can trigger unintended airbag deployment, injuring occupants; second, excessive circuit current during a collision can burn the contacts, preventing airbag deployment.

This fault constitutes an active safety system failure.

The vehicle remains drivable, but the airbag system enters degraded protection mode.

During a collision, the right knee airbag and any other airbags with related faults will fail to deploy.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Qin EV450 right knee airbag short circuit after wading

✓
A 2018 BYD Qin EV450 displayed "Check SRS System" on the dashboard after driving through floodwater during heavy rain. The scan tool retrieved B1727-00 (current fault). Inspection found water pooling in the front passenger footwell. After removing the front passenger seat and lower centre console trim, the knee airbag connector (located inside the front passenger seat rail) showed visible water staining and the terminals had green corrosion. Cleaning and drying the connector still yielded low resistance readings; further inspection revealed water had penetrated the airbag igniter. Replaced the right knee airbag assembly and resealed the floor waterproofing to resolve the fault.
BYD DTC AI Analysis

Qin 80 wiring harness crushed after accident repair

✓
One month after a front collision repair, this 2017 Qin 80 set DTC B1727-00. During the repair, the technician replaced the dashboard and passenger airbag but did not properly secure the knee airbag harness. Inspection found a screw at the dashboard frame mounting point had crushed the harness, damaging the insulation and causing a short to ground. They rerouted the harness, fastened it with dedicated clips, and made sure it had enough clearance from the frame edges. After repairing the insulation, the fault cleared; the airbag unit itself was not replaced.
BYD DTC AI Analysis

Qin 100 air conditioning water leak caused connector corrosion

✓
The owner reported that the airbag warning light occasionally illuminated. The scan tool retrieved historical fault code B1727-00. Inspection revealed a blocked passenger-side air conditioning evaporator drain hose, causing condensate to overflow onto the floor. The knee airbag connector, located above the passenger footwell, had been exposed to prolonged moisture, resulting in a micro-short between terminals. Cleaned the connector terminals, applied conductive anti-corrosion compound, unclogged the drain hose, and wrapped the connector with waterproof tape. Measured resistance returned to normal. One-month follow-up showed no recurrence.
BYD DTC AI Analysis

SRS module false alarm causing abnormal resistance

✓
2017 Qin EV300 frequently setting DTC B1727-00, but measured resistance of knee airbag and harness was normal (2.3Ω). Harness: no short circuits; airbag: intact. Suspected internal sampling circuit fault in SRS control module (ACU). Swapped in a known-good ACU from another vehicle for testing; fault transferred with the module. After reinstalling original ACU, fault returned. Replaced airbag control module and reconfigured vehicle VIN and crash sensor parameters. Fault permanently 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.