NO
AU
B171D-00

DTC B171D-00 indicates the resistance of the driver-side left knee airbag ignition circuit is below the normal threshold set by the SRS control unit (typically below 1 — Atto 3

Safety System

DTC B171D-00 indicates the resistance of the driver-side left knee airbag ignition circuit is below the normal threshold set by the SRS control unit (typically below 1.5Ω; the standard value is 1.6-2.4Ω).

This fault indicates a short circuit in the knee airbag ignition circuit.

Potential causes include an internal short in the airbag igniter coil, damaged wiring insulation causing a short between positive and negative circuits, or a short between connector terminals.

The SRS system identifies the airbag circuit as abnormal.

The knee airbag may fail to deploy during a collision or, in extreme cases, deploy unintentionally.

Consequently, the system illuminates the airbag warning light and logs this fault code.

3
Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV450 knee airbag connector shorted due to water ingress

✓
A 2018 Qin EV450 arrived with the airbag warning light constantly illuminated. Using VDS, we retrieved DTC B171D-00 (left knee airbag resistance too low). We removed the lower trim panel under the driver's side dashboard and found obvious water staining inside the knee airbag connector (yellow plug), with green corrosion on the terminals. The owner confirmed the vehicle had previously driven through water that reached floor level. Using a multimeter, we measured the knee airbag resistance at only 0.3Ω (severe short circuit). We cleaned and dried the connector terminals; the airbag unit resistance returned to the normal 2.1Ω. After reconnecting and clearing the DTC, the fault cleared. We recommend checking whether the AC drain hose is blocked, as this could cause water to leak onto the floor.
Original source ↗
BYD DTC AI Analysis

BYD Qin 100: Wiring harness chafed and shorted after accident repair

✓
A 2017 BYD Qin 100 came in with an illuminated airbag warning light after the dealership replaced the instrument panel assembly. The diagnostic tool showed DTC B171D-00. During installation of the new panel, the edge of the metal bracket pinched the left knee airbag wiring harness, damaging the insulation and shorting two internal wires. Resistance at the short measured 0.5Ω. The technician cut out the damaged section, re-soldered the joints and applied double-layer insulation, rerouted the harness away from the sharp bracket edges, and wrapped the harness with fleece tape for extra protection. After clearing the code, the system returned to normal.
BYD DTC AI Analysis

BYD Qin EV300 knee airbag internal squib short circuit

✓
A 2017 BYD Qin EV300 had an intermittent SRS light. The light sometimes turned off by itself after driving a distance. The fault occurred more often during cold starts. Retrieved DTC B171D-00. Live data showed the left knee airbag resistance fluctuating between 0.8–1.2 Ω, below normal. Disconnected the airbag connector and measured the airbag directly: 0.9 Ω and unstable. This indicated an intermittent short in the internal igniter coil. Replaced the left knee airbag module (Part No. SC-5820100). The new airbag measured 2.0 Ω, the standard value. Performed SRS configuration after installation. That completely resolved the fault.
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.