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 — Qin Plus

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 — Qin Plus
  • 1Sensor body internal circuit damage: 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 a loose connector, oxidized terminals, broken wiring harness, or short to ground or power in the left front longitudinal beam area.
  • 3Installation issue: Incorrect sensor installation after front-end accident repairs, deformed mounting bracket causing abnormal stress on the sensor, or incorrect fastening torque (standard is usually 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  • 4SRS control module misjudgment: An internal A/D conversion circuit fault or outdated software version causes the module to misinterpret sensor signals.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 power supply abnormality: Aftermarket high-power electrical equipment causes power supply voltage fluctuations, or excessive voltage drop occurs in the sensor power supply circuit.
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 the freeze frame data. Turn off the ignition switch, disconnect the battery negative 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 beam or below the headlamp bracket) for physical damage, cracks, or signs of water ingress. Inspect the mounting bracket for deformation and verify correct sensor installation orientation (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, back-out, or looseness. Use a multimeter to measure the harness side: the power terminal should measure 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 is approximately 2-3kΩ; refer to the workshop manual for exact specifications). Replace the sensor if the resistance is infinite or close to 0Ω. If conditions permit, use an oscilloscope to monitor signal waveform changes during a collision simulation.
  • 5
    Replacement and matching: If you confirm a sensor fault, replace the left front frontal collision sensor with a genuine part (part number: BYD-XXX; verify based on 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 on the power, and clear the fault code. Perform the SRS system self-check (takes a few seconds to a few minutes) and confirm the airbag warning light turns off. Road test to confirm the fault does not recur.
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 Qin Plus Fault Codes
B1108For 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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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]