AU
B165800

This DTC indicates a communication link fault between the SRS (Supplemental Restraint System) control unit and the Left Front Impact Sensor (LFIS) — Atto 3

Safety System

This DTC indicates a communication link fault between the SRS (Supplemental Restraint System) control unit and the Left Front Impact Sensor (LFIS).

This typically indicates an interrupted LIN bus or private CAN communication between the sensor and the Airbag Control Module (ACM), a data validation failure, or a signal timeout.

The LFIS monitors deceleration changes in the vehicle's left front area and provides the SRS control unit with critical collision severity data to determine whether to deploy the driver airbag, left curtain airbag, and seatbelt pretensioner.

This communication fault prevents the control unit from receiving collision information for this zone.

Consequently, it may cause unintended airbag deployment (fail-safe mode) or delay or prevent the activation of left-side protection devices during an actual collision.

This constitutes a critical fault in the active safety system.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Water ingress, oxidation, or backed-out pins in the left front crash sensor wiring harness connector: This sensor is located near the left front longitudinal beam or bumper bracket. Poor connector sealing allows water entry after wading, washing the vehicle, or driving in the rain, causing terminal corrosion and increased contact resistance.
  • 2Sensor power supply or ground circuit fault: includes blown fuses and open or short circuits (especially after front-end collision repairs, where improperly secured wiring harnesses rub against metal body edges and damage the insulation).
  • 3Left front crash sensor internal fault: A damaged internal accelerometer or communication chip prevents the sensor from responding to the SRS control unit handshake signal.
  • 4SRS control unit (airbag ECU) internal communication port fault: Damaged control unit circuit module receiving this specific channel signal.
  • 5Harness shielding failure or electromagnetic interference: Damage to the front compartment harness shielding causes high-frequency interference, resulting in communication data packet checksum failure.
What To Do
  • 1
    Use the BYD VDS2000 or Launch X431 diagnostic tool to access the SRS system. Read the complete fault codes and record the freeze frame data. Confirm if B165800 is a current fault (Present) or a history fault (History), and check for related fault codes (such as B165700 parameter error).
  • 2
    Disconnect the battery negative terminal and wait 3 minutes for the SRS capacitor to fully discharge for safety. Locate the left front crash sensor (usually mounted on the front section of the left front longitudinal beam or behind the headlamp bracket). Inspect the sensor housing for physical damage, cracks, or signs of water ingress.
  • 3
    Disconnect the sensor connector and inspect the terminals for oxidation, backed-out pins, or terminal spread. Clean the terminals with electronic contact cleaner and apply a conductive protectant. Measure the resistance between the sensor-side terminals to verify no internal short circuit exists (standard value: infinite or manufacturer specified value).
  • 4
    Reconnect the connector. Turn the ignition switch to ON (do not start). Use a multimeter to measure the sensor supply voltage (should be 9-16 V, depending on model), ground resistance (should be less than 1 Ω), and LIN line voltage (typically a 7-11 V pulsed voltage, average value approx. 9 V).
  • 5
    If voltage is abnormal, disconnect the SRS control unit connector and use an oscilloscope to check the LIN bus waveform. Verify the control unit sends the correct wake-up signal (typically a 12V high level or a specific frequency square wave). Measure wiring harness continuity, inspecting the harness mounting point on the front left longitudinal member in the front compartment for wear.
  • 6
    If wiring harness measurements are normal, perform a sensor substitution test: Replace the left front crash sensor with a known good unit, clear the fault code, perform an ignition cycle test, and use the diagnostic tool to execute the 'Crash Sensor Calibration' procedure (some models require a dedicated calibration tool).
  • 7
    If the fault persists after replacing the sensor, check the SRS control unit software version and upgrade it if necessary. If the software version is correct, this indicates an internal SRS control unit fault. Replace the control unit and reconfigure the vehicle VIN and sensor parameters.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Left front crash sensor communication lost after water ingress

✓
A 2019 BYD Qin Pro DM had an airbag warning light that stayed on after driving in heavy rain. The system stored DTC B165800. Inspection found obvious water staining inside the collision sensor connector below the left front longitudinal beam, with green corrosion on the terminals. The front bumper undertray had cracked during a previous underbody scrape, allowing water to be forced into the sensor connector when driving through standing water. Repair involved thoroughly cleaning the connector with precision electronic cleaner, replacing the waterproof seal, and applying waterproof insulating tape to the connector. After clearing the fault code and performing three ignition cycle tests, the fault did not recur.
BYD DTC AI AnalysisFrom Chinese market (translated)

After accident repair, a loose wiring harness connection caused an intermittent communication fault.

✓
2018 Qin Pro petrol variant. After a minor collision on the left front, the dealership replaced the left front fender and bumper. One week later, the airbag warning lamp illuminated intermittently, and the diagnostic tool displayed intermittent fault code B165800. Inspection found that during the repair, the left front impact sensor wiring harness connector had not been fully locked — its retaining clip was only partially engaged, causing intermittent contact as the vehicle moved. Fix: Re-routed and secured the wiring harness, made sure the connector clip clicked fully into place, then used cable ties to fix the harness to the longitudinal beam bracket to stop movement. After a month of monitoring, the fault has not recurred.
BYD DTC AI AnalysisFrom Chinese market (translated)

Hard fault due to sensor body damage.

✓
2019 BYD Qin Pro DM. Airbag warning light stays on continuously. DTC B165800 present and could not be cleared. Checked sensor power supply (12.4V) and ground (0.3Ω) — both normal. LIN line voltage measured 0V with ignition ON (should normally read approx 9V pulse). Diagnosed internal short in sensor pulling bus low. Removed sensor and found fine cracks on its housing, likely from stress during a previous bottoming-out impact. Replaced with a new left front impact sensor. Used VDS2000 to perform SRS system configuration and impact sensor zero calibration. Fault resolved. System returned to normal self-check status.
BYD DTC AI AnalysisFrom Chinese market (translated)

False positive caused by software calibration error

✓
A 2018 BYD Qin Pro displayed DTC B165800 after a battery replacement. The vehicle had no collision history, and the wiring harness measured normal. Diagnosis found the battery was disconnected too long during the swap, causing the SRS control unit to lose sensor calibration data stored in non-volatile memory. Fix: Use the BYD dedicated diagnostic tool to enter SRS special functions, then run "Sensor ID Registration" and "Longitudinal/Lateral Acceleration Zero-Point Calibration." Clear the DTC after completing both—the airbag warning light goes out. This fault tends to occur when the battery is disconnected for more than 30 minutes. It's a software configuration issue, not a hardware failure.
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]