AU
B165F00

DTC B165F00 indicates the SRS (Supplemental Restraint System) ECU detected a functional fault or communication error in the right front impact sensor — Seal U

Safety System

DTC B165F00 indicates the SRS (Supplemental Restraint System) ECU detected a functional fault or communication error in the right front impact sensor.

This sensor mounts near the right front side member or bumper reinforcement beam.

It detects deceleration changes during a frontal collision and sends a crash signal to the airbag control unit.

The '00' in the fault code typically indicates an internal sensor self-test failure, an out-of-range signal, or a communication interruption between the sensor and the ECU (non-specific short or open circuit).

This fault disables the right front crash detection circuit.

During a frontal collision, this failure may delay or prevent the deployment of the right front airbag and side curtain airbags, severely compromising passive safety performance.

Consequently, the SRS illuminates the airbag warning light and may disable related airbag functions.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Internal sensor fault: A damaged accelerometer element inside the right front crash sensor or a signal processing circuit failure causes an abnormal output signal or no response. This commonly occurs after minor frontal impact vibrations or natural component aging.
  • 2Wiring harness connector issue: The sensor connector in the right front fender or bumper is loose, oxidized, corroded, has backed-out pins, or has water ingress. Poor contact frequently results from an improperly seated connector after driving through water, washing the vehicle, or performing collision repairs.
  • 3Physical damage to the wiring harness: Accident repairs or front bumper removal and installation can crush, chafe, or break the right front wiring harness, causing an intermittent open circuit in the signal wire, power wire (12V), or ground wire.
  • 4Abnormal installation position: A loose sensor retaining bolt or deformed sensor mounting bracket causes the sensor installation angle to deviate from the design position, affecting collision signal detection accuracy and triggering the fault code.
  • 5SRS ECU communication fault: Abnormal impedance or electromagnetic interference on the dedicated communication line between the sensor and the ECU (usually a PWM signal or CAN line), or a fault in the ECU internal receiving circuit, causes data verification failure.
What To Do
  • 1
    Initial diagnosis and freeze frame recording: Use the dedicated diagnostic tool (VDS or ED400) to read complete DTC information and record freeze frame data (vehicle speed, timestamp, etc., at the time of the fault). Verify B165F00 is a current fault (Active) and check for other related crash sensor fault codes (such as B165E11 short to ground).
  • 2
    Visual and physical inspection: Turn off the ignition. Remove the right front bumper or fender liner. Inspect the right front crash sensor for damage or cracks. Check the installation torque (usually 8-10N·m). Confirm the sensor direction arrow points directly to the front of the vehicle. Verify the connector is fully locked and the sealing ring is intact.
  • 3
    Wiring harness continuity test: Disconnect the battery negative terminal, then disconnect the SRS ECU and right front sensor connectors. Use a multimeter to measure the end-to-end resistance of the sensor harness: power wire (should be <1Ω), ground wire (should be <1Ω), and signal wire (should be <1Ω). Measure the insulation resistance of each wire to ground and to power (should be >10MΩ) to eliminate potential open or short circuits in the wiring harness.
  • 4
    Sensor electrical parameter measurement: Reconnect the battery and turn the ignition switch to ON. Do not disconnect the sensor connector. Use a back-probe pin to measure the sensor supply voltage (should be 9-16 V, normally 12 V) and the signal wire voltage (static voltage is typically 2.5 V or a 5 V reference, depending on the vehicle model). If the voltage is abnormal, check the upstream wiring.
  • 5
    Replacement Verification and System Reset: Perform a substitution test using a known-good sensor with the same part number. Clear the fault code, then perform a road test or simulation test (some models support a sensor self-test via the diagnostic tool). If the fault disappears, the original sensor is faulty. After installing a new sensor on certain Qin PRO models, execute the 'SRS System Configuration' or 'Crash Sensor Calibration' function via the diagnostic tool so the ECU recognizes the new sensor parameters.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Intermittent right front impact sensor fault after water wading

✓
2018 BYD Qin Pro DM. The owner reported the airbag warning light intermittently illuminates after driving in rain. The diagnostic scanner retrieved code B165F00 (current fault); historical data showed the fault mostly occurred after rain. Inspection found an aftermarket radar fitted under the right front bumper with poor sealing. Disassembly revealed green copper corrosion inside the sensor connector; oxidised pins caused increased signal resistance (measured 12 Ω, normal <1 Ω). Cleaned the connector pins, applied conductive grease, and reapplied the waterproof seal. Fault resolved. Advised the owner to inspect the front bumper sealing strip and avoid directing high-pressure water at the sensor area.
BYD DTC AI AnalysisFrom Chinese market (translated)

Uncalibrated sensor after accident repair caused fault.

✓
2019 Qin Pro petrol variant. After a minor frontal collision, a repair shop replaced the right front wing and bumper. After repairs, the instrument panel continuously displayed the airbag warning light. Retrieved fault codes B165F00 and B165A00 (left front sensor parameter error). Inspection found that although the right front impact sensor was new, its mounting bracket was not fully flush with the chassis rail during installation, sitting at approximately 5 degrees of tilt. More critically, the shop had not performed the 'SRS system configuration' function on the diagnostic tool after replacing the sensor, so the ECU could not recognise the new sensor's ID and calibration parameters. After reinstalling the sensor to standard torque and using VDS to perform SRS system configuration and impact sensor zero-point calibration, the fault codes cleared and the system returned to normal self-check.
BYD DTC AI AnalysisFrom Chinese market (translated)

Wiring harness wear caused intermittent signal loss.

✓
A 2019 BYD Qin Pro DM with 80,000 km on the clock came in with the airbag warning light illuminating intermittently, occasionally going out after driving for a while. Diagnosis revealed DTC B165F00 as an intermittent fault. Inspection focused on the right front wiring harness, revealing chafing at the transition from the body harness to the front bumper, specifically at the wheel arch liner fixing clip. The signal wire insulation had worn through, causing an intermittent short to earth (measured resistance to earth fluctuating between 2-50 MΩ). Repaired the damaged wiring, reinforced the insulation with heat shrink tubing, and rerouted the harness to avoid contact with metal edges, which completely resolved the fault. This issue is common in vehicles where wiring has been incorrectly secured following accident repairs.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal sensor components failed due to ageing

✓
2018 BYD Qin Pro petrol, 60,000 km. Airbag warning light stayed on. Diagnostics showed only one active DTC: B165F00. Visual inspection of sensors and wiring harness found no abnormalities. 12V power supply and ground measured normal, but signal voltage jumped erratically between 0.3V and 4.8V (normal: stable reference voltage). After swapping the left and right front crash sensors, the fault moved to the left side (DTC B165E00 appeared), confirming internal accelerometer or signal-processing IC damage in the original right-hand sensor. Replaced with a genuine sensor of the same part number (hardware versions vary by model year – verify part number). Cleared fault codes, ran system self-test (passed), and the warning light went out.
Other Seal U 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]