AU
B165600

This fault code indicates the SRS (airbag) control module detects an abnormal signal from the Left Front Impact Sensor or an internal sensor fault — Atto 3

Safety System

This fault code indicates the SRS (airbag) control module detects an abnormal signal from the Left Front Impact Sensor or an internal sensor fault.

The Left Front Impact Sensor mounts to the front section of the left front longitudinal rail or near the headlamp bracket to detect deceleration changes during a frontal collision.

The SRS module sets DTC B165600 when it detects a sensor signal voltage outside the normal range (typically 0.5-4.5V), a signal interruption, or an internal sensor self-check failure.

This fault degrades frontal collision protection.

In extreme cases, it may prevent the front airbags from deploying correctly during a collision or cause unintended deployment.

The sensor uses a piezoelectric or capacitive accelerometer and communicates with the SRS module via a hardwired connection.

The fault may involve the 12V sensor power supply, ground, or signal circuit (PWM or analog signal).

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Internal circuit damage in the sensor body: Piezoelectric element aging, internal IC chip failure, or seal failure causing water ingress and corrosion, resulting in signal drift or no signal output.
  • 2Wiring harness and connector fault: Vibration, water ingress, or accidents during vehicle operation cause loose connectors, oxidized terminals, wiring harness breakage, or a short to ground or power in the left front longitudinal beam area wiring harness.
  • 3Installation issue: Incorrect sensor installation after front-end accident repairs, deformed mounting bracket causing abnormal stress on the sensor, or incorrect fastening torque (typical standard: 8-10 N·m).
  • 4SRS control module misjudgment: An internal A/D conversion circuit fault or outdated software version causes the module to misinterpret sensor signals.
  • 5Electromagnetic interference or abnormal power supply: Aftermarket high-power electrical equipment causes power supply voltage fluctuations, or the sensor power supply circuit has excessive voltage drop.
What To Do
  • 1
    Safety preparation: Use a diagnostic tool (VDS or dedicated equipment) to read all DTCs, confirm B165600 is a current fault (Active), and record freeze frame data. Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors.
  • 2
    Visual inspection: Inspect the left front crash sensor (located at the front of the left front longitudinal rail or below the headlamp bracket) for physical damage, cracks, or signs of water ingress. Inspect the mounting bracket for deformation and verify the correct sensor installation direction (arrow pointing toward the front of the vehicle).
  • 3
    Circuit inspection: Disconnect the sensor connector (usually 2-3 pins) and inspect the terminals for corrosion, backed-out pins, or looseness. Measure the wiring harness side using a multimeter: the power terminal should read 12V (Ignition ON), the ground terminal resistance to ground should be less than 1Ω, and the signal terminal voltage to ground should be approximately 2.5V (static). Measure circuit continuity and insulation to confirm no short or open circuits.
  • 4
    Sensor test: Measure the sensor resistance (normal value approx. 2-3 kΩ; refer to the workshop manual for exact specifications). Replace the sensor if the resistance is infinite or close to 0 Ω. If conditions permit, use an oscilloscope to monitor signal waveform changes during a collision simulation.
  • 5
    Replacement and matching: If confirming a sensor fault, replace with a genuine left front frontal collision sensor (part number: BYD-XXX; verify for the specific vehicle model). Some models require using a diagnostic tool to perform the 'SRS sensor calibration' or 'configuration write' function.
  • 6
    Verification: Reconnect all components, turn the power ON, and clear the fault code. Perform an SRS system self-check (takes a few seconds to a few minutes) and verify the airbag warning light turns off. Road test the vehicle to confirm the fault does not reappear.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor corroded due to water ingress on wading vehicle

✓
2019 BYD Qin Pro DM, 30,000 km. Two days after driving through heavy flooding, the airbag warning light came on the dash. Scanned and found current DTC B165600. Removed the front left bumper and found the left front impact sensor mounted low on the left front chassis rail. The sealing ring had deteriorated, allowing water ingress; the internal circuit board showed clear water stains and oxidation. Measured infinite resistance (open circuit) across the sensor. Fitted a new left front impact sensor, cleaned the wiring harness connector, and applied corrosion protection. Cleared the fault code—it has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

Poor wiring harness connection after accident repair

✓
2018 Qin Pro petrol model. After a front-end collision repair at an unauthorised shop, the airbag warning light came on intermittently one week later. Diagnosis found intermittent DTC B165600. Inspection revealed the left front impact sensor harness connector latch had not been fully locked during the repair; vibration while driving caused the connector to disconnect intermittently. Reconnected the connector, ensured the latch locked fully in place, then used cable ties to secure the harness and relieve strain. The fault was permanently eliminated.
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor body aged and failed.

✓
2019 BYD Qin Pro DM, 85,000 km, no collision history. Dashboard suddenly displayed an airbag fault. Scan found DTC B165600 currently present. Power supply and ground at the sensor measured normal. Disconnected the sensor; internal resistance measured 5.2 kΩ (spec 2.0–3.0 kΩ). Determined internal piezoelectric element aging caused signal drift. Replaced the left front impact sensor. SRS self-test passed, fault light went out. One-week follow-up: no recurrence.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS module false alarm resolved with software update

✓
2018 BYD Qin Pro. The owner reported the airbag warning light came on after a multimedia system update. The scan tool retrieved DTC B165600. The sensor wiring and component were normal, with resistance and voltage within spec. A technical bulletin indicated early SRS software versions on this model can set false fault codes. Upgraded the SRS control module software from V1.2 to V2.4. Cleared the fault code, and it did not return. This was a false alarm caused by software compatibility issues.
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]