AU
B165700

DTC B165700 indicates abnormal configuration parameters for the Left Front Impact Sensor — Seal U

Safety System

DTC B165700 indicates abnormal configuration parameters for the Left Front Impact Sensor.

This sensor is a critical component of the SRS (Supplemental Restraint System/Airbag System) and detects frontal collision acceleration. "Parameter error" indicates the calibration data, configuration code, or communication protocol stored within the sensor does not match the SRS control module (ACU), or the sensor's physical installation angle/position deviates from the design specification.

This fault may cause: 1) Delayed or failed airbag deployment during a collision; 2) Unintended airbag deployment in non-collision scenarios; 3) Vehicle high-voltage interlock shutdown (some models cut off high voltage upon detecting abnormal collision signals).

Unlike DTC B165600 (hardware fault) and B165800 (communication fault), this fault relates specifically to data configuration and installation geometry parameters.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Improper physical installation of the sensor: Deformed or loose mounting bracket, or incorrect installation direction (sensor directional arrow must point toward the front of the vehicle), causing the installation angle deviation to exceed the ±5° allowable range.
  • 2Poor connector contact: Oxidation, corrosion from water ingress, terminal back-out, or insufficient contact pressure at terminals (e.g., in plug KJG05-18) causes configuration data read errors or power supply voltage fluctuations.
  • 3Low-voltage power supply system fault: DC-DC converter failure causes unstable output voltage (outside the 9-16V range), or a loose ground point affects sensor internal memory data integrity.
  • 4Wiring harness interference or wear: The wiring harness inside the left front A-pillar chafes against the rear wiper wiring harness or vehicle body metal edges, causing a signal wire short circuit or electromagnetic interference that results in configuration parameter transmission errors.
  • 5Software configuration lost: Vehicle power disconnection during repairs, a discharged battery, or outdated SRS module software causes the loss or verification failure of configuration data, such as sensor ID codes and sensitivity parameters.
What To Do
  • 1
    Connect the VDS or Launch X-431 diagnostic tool and access the SRS system. Read all fault codes and freeze frame data. Check for associated fault codes such as B167200 (right side sensor fault), B17A400 (SRS hardwire signal abnormality), or U029800 (DC communication fault).
  • 2
    Visually inspect the left front crash sensor installation: verify the sensor retaining bolt torque (usually 8-10 N·m), check the mounting bracket for deformation, and verify the sensor arrow points directly to the front of the vehicle with no tilt or rotation.
  • 3
    Disconnect the battery negative terminal and wait 90 seconds to discharge the SRS capacitor. Unplug the left front crash sensor connector (usually located on the left front longitudinal beam or inside the fender) and inspect the terminals for oxidation, water ingress (white or green corrosion marks), backed-out pins, or looseness.
  • 4
    Use a multimeter to measure the sensor power supply (Pin 1 is usually +B, Pin 2 is ground): Turn the ignition switch to the ON position. The voltage should be between 9-16 V, and the difference from the battery voltage should be less than 0.5 V. Measure the ground resistance; it should be less than 1 Ω.
  • 5
    Check wiring harness routing: Inspect the wiring harness along the left front A-pillar and inside the sill trim for wear or pinch marks, especially at interference points with the rear wiper harness and instrument panel frame. If necessary, repair the insulation layer using electrical tape and corrugated conduit.
  • 6
    Cleaning procedure: Clean the connector terminals with electrical contact cleaner, blow dry, and apply conductive grease (Vaseline or specialized contact grease). Verify the waterproof sealing ring is intact, then reconnect fully until it clicks.
  • 7
    Recalibration: Connect the diagnostic tool, enter the SRS system special functions, and execute the 'Crash Sensor Configuration' or 'System Calibration' procedure (some models require entering the sensor ID code or automatic identification). Verify the tool displays 'Configuration Successful'.
  • 8
    Clear the fault code. Turn off the ignition, wait 30 seconds, then power on again and confirm the fault code does not reappear. Perform a road test (including rough roads and turns) and verify the SRS warning light remains off.
  • 9
    Related system check: Access the BMS and VCU systems and check for fault codes such as P1AC000 (collision warning) and P1A5100 (collision hardwire PWM abnormality). If present, clear them simultaneously and verify normal high-voltage system operation.
  • 10
    Pre-delivery inspection: Confirm the vehicle displays no other warning lights, test low-voltage electrical equipment (such as the horn and wipers) for normal operation, and advise the customer to monitor for recurrence within 1 week.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD E2 Intermittent SRS Warning Light – Abnormal Collision Signal in Multiple Systems

✓
Symptoms: Intermittent SRS warning light on the BYD E2 dashboard, no other driving abnormalities. Diagnosis: Scanned SRS system and retrieved codes B165700 (Left Front Impact Sensor Configuration Error) and B167200 (Right Side Impact Sensor Parameter Error). The vehicle control module stored B17A400 (SRS Hardwire Signal Abnormal), and the BMS stored P1A5100 (Collision Hardwire Signal PWM Abnormal). Inspection found the left front impact sensor connector loose and the mounting bracket slightly deformed. Resolution: Realigned the sensor mounting position and tightened to specified torque. Cleaned connector terminals and reseated the plug firmly. Performed SRS system calibration, cleared fault codes, and road tested for 30 km with no fault recurrence.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Dolphin low-voltage power supply fault caused sensor configuration error

✓
Symptoms: While driving, the Dolphin's instrument panel displayed "Please check low voltage power supply system fault", the SRS warning light illuminated, and acceleration was weak. Diagnosis: VDS scan showed the Battery Management System reporting U029800 (Communication fault with DC) and the SRS system reporting B165700 (Left front impact sensor configuration error). Measurements found the DC-DC converter output voltage fluctuating between 8–15V, causing unstable power to the impact sensor and loss of configuration data. Resolution: Replaced the DC-DC converter. After restoring a stable low-voltage power supply, recalibrated the left front impact sensor, cleared all fault codes, and road tested to verify power was restored and the SRS warning light went out.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro DM-i wiring harness interference caused power limitation

✓
Symptoms: When operating the rear wiper on the Song Pro DM-i, the instrument panel displayed "Power Limited" and the SRS warning light came on. Diagnosis: Scanned the SRS system and retrieved DTC B165700 (Left Front Impact Sensor Configuration Error). Inspected the wiring harness inside the left front A-pillar and found the impact sensor harness rubbing against the rear wiper harness, causing signal interference. Resolution: Rerouted the wiring harness to separate the SRS sensor circuit from the rear wiper circuit. Repaired the damaged insulation on the worn harness. Reconfigured the left front impact sensor parameters. Updated the SRS control module software to the latest version. Road tested and confirmed the fault was fixed.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Yuan Pro DC communication fault associated with SRS malfunction

✓
Symptom: After powering on the Yuan Pro, the low voltage battery warning light and SRS warning light on the instrument panel illuminate intermittently. Diagnosis: VDS scan found Battery Management System DTC U029800 (communication fault with DC-DC converter) and SRS DTC B165700 (left front impact sensor configuration error). Inspection found poor contact in the DC-DC converter output circuit and corrosion on the impact sensor connector. Resolution: Repaired the poor contact at the DC-DC converter output terminals, cleaned the impact sensor connector and reconnected it securely, reconfigured and calibrated the left front impact sensor, cleared the fault codes, then road tested to verify.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Water ingress corroded the KJG05 connector, causing airbag signal faults on a BYD new energy vehicle.

✓
Symptoms: Intermittent EV mode failure with SRS warning light on the dash. System recovered after about 2 minutes. Diagnosis: Battery management system logged P1AC000 (Airbag ECU collision alert), and SRS system logged B165700 (Left front impact sensor configuration error). Continuity on the airbag collision signal circuit between terminals G10A-10 and K45B-3 tested normal. However, inspection of connector KJG05 terminal 18 revealed liquid ingress causing terminal corrosion. Resolution: Cleaned connector KJG05 to remove corrosion, applied waterproof sealing, reconfigured left front impact sensor, cleared fault codes, and road tested over 30 km. Delivered vehicle to customer for one week of observation. Follow-up confirmed the fault is completely gone.
Original source ↗
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]