AU
B165D00

DTC B165D00 indicates the airbag control unit (SRS ECU) detects a communication interruption or physical connection loss with the Right Front Frontal Impact Sensor — Atto 3

Safety System

DTC B165D00 indicates the airbag control unit (SRS ECU) detects a communication interruption or physical connection loss with the Right Front Frontal Impact Sensor.

This sensor typically mounts inside the right front bumper reinforcement beam or at the front of the right fender to monitor collision acceleration at the right front of the vehicle.

The SRS ECU sets this fault code if it fails to receive a valid signal from the sensor within a predefined cycle, or if it detects an open circuit or abnormal resistance in the sensor circuit.

The airbag system then enters fail-safe mode, which may prevent the right front airbag, side airbag, or seat belt pretensioner from deploying normally during a collision.

The instrument cluster airbag warning light remains illuminated, and some models may sound a warning buzzer.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Sensor wiring harness connector loose, disconnected, or poor contact: Commonly caused by an unseated connector or broken retaining clip after front bumper removal and installation, accident repairs, or water exposure.
  • 2Wiring harness open or short circuit: A front-end collision stretched and broke the wiring harness, long-term chafing against the fender or bumper reinforcement damaged the harness, or rodent chewing shorted the signal wire to ground.
  • 3Crash sensor internal fault: Internal accelerometer damage, electronic component aging, or seal failure causes an internal short circuit. This prevents the sensor from returning the correct resistance value (normally 2-3kΩ) to the SRS ECU.
  • 4Mounting bracket or ground fault: A loose sensor retaining bolt causes insecure mounting, or an oxidized or loose sensor ground point creates a poor circuit, affecting signal transmission.
  • 5SRS ECU communication port fault: Damaged internal control unit pin communicating with the right front sensor, or software logic error (rare; confirm after ruling out wiring faults).
What To Do
  • 1
    Safety preparation: Turn the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the airbag system capacitor and prevent accidental airbag deployment during repair.
  • 2
    Location and inspection: Remove the right front bumper cover or right fender liner, locate the right front impact sensor (usually marked 'Front Impact Sensor' or with a part number), and visually verify that the connector is fully seated, the locking tab is intact, and the wiring harness shows no external damage.
  • 3
    Voltage measurement: Reconnect the battery. Turn the ignition switch to the ON position (do not start). Use a multimeter to measure the sensor connector terminals: verify 12V battery voltage (B+), good ground (GND), and signal voltage (typically around 2.5V reference voltage). If power or ground is missing, check wiring harness continuity.
  • 4
    Circuit continuity test: Disconnect the SRS ECU connector (located under the center console or center tunnel). Use a multimeter to measure the harness resistance between the ECU and the sensor; resistance must be less than 1 Ω. Measure the insulation resistance of each wire to ground and to power; resistance must be greater than 10 MΩ to rule out a short circuit.
  • 5
    Sensor body test: Turn off the ignition switch, disconnect the sensor connector, and measure the resistance between the two sensor terminals. The resistance should be 2-3 kΩ (refer to the vehicle repair manual for specifics). If the resistance is 0 or infinite, or if the resistance deviation exceeds ±10%, replace the sensor.
  • 6
    Replacement and installation: If the sensor is faulty, replace it with a genuine part (some models require VIN matching). Install to the standard torque (typically 8-10 N·m). Point the sensor arrow directly toward the front of the vehicle. Fully seat the connector and secure the wiring harness to prevent interference.
  • 7
    System calibration: Connect a dedicated diagnostic tool (VDS or Launch/Autel equipment supporting the BYD SRS system), clear the fault code, execute the 'SRS System Configuration' or 'Crash Sensor Calibration' procedure, perform an ignition cycle test, and confirm B165D00 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

New vehicle PDI case: Transport plug not connected

✓
Symptoms: During pre-delivery PDI inspection of a 2019 BYD Qin Pro DM, the airbag warning light stayed on constantly. The diagnostic tool read fault code B165D00. Diagnosis: Checked the impact sensor on the inner side of the right front bumper. Found the sensor connector completely unplugged, just loosely attached (during transport). Measured wiring harness voltages: 12V supply, ground, and 2.4V signal — all normal. Measured sensor resistance: 2.8kΩ, normal. Fix: Reconnected the connector properly and confirmed the locking clip fully engaged. Cleared the fault code with the diagnostic tool and ran three ignition cycle tests. The warning light went out and the fault code did not return.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Intermittent connection due to pinched wiring harness after accident repair

✓
Symptoms: 2018 BYD Qin Pro petrol variant. Airbag warning light illuminated after minor front collision repairs, DTC B165D00. Diagnosis: Right front sensor connector visually OK, but signal wire voltage measured only 0.8 V (low). Traced the harness and found the wiring pinched between the bumper reinforcement and fender when the front bumper was reinstalled, causing partial copper wire breakage and high resistance. Solution: Repaired damaged harness (cut out damaged section, re-soldered wires, sealed with heat-shrink tubing). Rerouted wiring away from pinch points and secured with cable ties. Cleaned sensor connector terminals, applied conductive grease. Cleared fault codes, road test confirmed normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Connector oxidation and corrosion after wading

✓
Symptoms: 2020 BYD E3 airbag warning light illuminated after driving through water. Diagnostics showed right front impact sensor disconnected. Diagnosis: Removed the right front fender liner and found visible water stains and green corrosion inside the sensor connector. Pin oxidation caused excessive contact resistance (measured 15 Ω, normal <1 Ω). Sensor body resistance and wiring harness continuity were normal. Repair: Cleaned the plug and socket terminals thoroughly with electronic contact cleaner, applied dielectric grease for waterproofing, replaced the waterproof seal, reconnected the connector, and cleared the fault codes. Fault resolved. Recommend inspecting the front bumper seal to prevent recurrence.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Internally damaged sensor body replacement case

✓
Symptoms: 2019 BYD E2, no accident history. Airbag warning light illuminates intermittently, especially during cold starts. DTC B165D00 appears intermittently. Diagnosis: Inspected wiring harness connections – normal. Measured sensor resistance cold at 5.2kΩ (exceeds normal 2–3kΩ range). After warming up, thermal expansion and contraction inside the sensor changed resistance, sometimes restoring normal communication. Tapped the sensor housing lightly; resistance fluctuated noticeably. Diagnosed as faulty internal accelerometer or circuit board solder joint. Repair: Replaced the right front impact sensor assembly (part number matched to VIN). Oriented the arrow parallel to the vehicle's longitudinal axis during installation. Torqued to 9 N·m. Performed system configuration with diagnostic tool; fault cleared completely.
Original source ↗
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself. Sources: [1]