AU
B165E

DTC B165E indicates the Right Front Impact Sensor detects a low-impedance or zero-impedance circuit, meaning the sensor signal wire or power wire is shorted to body ground — Seal U

Safety System

DTC B165E indicates the Right Front Impact Sensor detects a low-impedance or zero-impedance circuit, meaning the sensor signal wire or power wire is shorted to body ground.

This piezoelectric acceleration sensor monitors collision deceleration at the front right side of the vehicle.

A short to ground prevents the SRS ECU from receiving the correct collision signal and triggers a Level 3 severe fault: 1) the right-side airbag and seat belt pretensioner may fail to deploy in time during a collision; 2) the system may falsely report a collision signal, causing unintended deployment; 3) the entire SRS system enters fail-safe mode, restricting all airbag functions.

Typical causes for this fault include damaged wiring harness insulation, water ingress in the connector, an internal sensor short circuit, or an ECU drive circuit fault.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Wiring harness chafing in the right front side member area: During vehicle operation, the wiring harness rubs against body metal edges, retaining clips, or the front bumper bracket. This prolonged friction damages the insulation and causes a short to ground. Common causes include improperly secured harnesses after accident repairs or underbody scraping.
  • 2Sensor connector water ingress and corrosion: Car washing, wading, or poor front sealing allows water into the connector (usually located inside the right front fender liner or below the headlamp). Pin oxidation causes a short to ground, accompanied by white or green corrosion marks.
  • 3Internal sensor circuit fault: Internal breakdown of the piezoelectric element or signal processing chip causes a power supply short to ground. Physical damage to the sensor housing or internal seal failure usually accompanies this fault.
  • 4Airbag ECU internal drive circuit fault: The ECU internal constant-current source circuit supplying power to the sensor is faulty, causing the ECU to incorrectly identify a normal sensor as shorted to ground. Verify by substitution.
  • 5Improper front-end collision repair: Failing to route the wiring harness along the standard path after replacing the front bumper, headlight, or longitudinal beam allows screws, cable ties, or metal edges to pinch the harness, causing a short circuit.
What To Do
  • 1
    Safety Preparation: Turn off the ignition switch. Disconnect the 12V battery negative terminal and wait at least 90 seconds to discharge the SRS capacitor. Wear an anti-static wrist strap. Avoid using a multimeter resistance setting to measure the airbag circuit directly.
  • 2
    Fault confirmation and freeze frame analysis: Use the diagnostic tool to read the DTC B165E status (current/history). Record the vehicle speed and sensor voltage values from the freeze frame data. Confirm the environmental conditions when the fault occurred.
  • 3
    Visual inspection: Remove the right front bumper cover and right front fender liner. Check the crash sensor (located at the front of the right front longitudinal rail or headlamp bracket) for deformation. Inspect the wiring harness for damage, burn marks, or crush marks. Inspect the connector for looseness, water ingress, or corrosion.
  • 4
    Harness insulation test: Disconnect the SRS ECU connector (located under the center console or center tunnel) and the right front crash sensor connector. Use a multimeter to measure the resistance between the signal terminal on the sensor harness side (usually G10-3 or corresponding pin) and body ground. Normal resistance is greater than 1 MΩ. A reading below 1 Ω confirms a short to ground.
  • 5
    Locate the short circuit in sections: gradually strip the wiring harness insulation from the sensor end toward the ECU end. Inspect the sections passing through the longitudinal beam holes, firewall, and fender to find where the wiring harness shorts to the body ground. Use an oscilloscope or dedicated diagnostic tester to check circuit capacitance and continuity.
  • 6
    Component replacement verification: If the wiring harness is normal, replace the right front frontal collision sensor (part number varies by model, e.g., Yuan EV: EG-3636100). During installation, tighten to 8-10 N·m. Verify the mounting surface is clean and free of paint.
  • 7
    System reset and calibration: Reconnect all connectors and the battery. Clear the fault codes. Use the diagnostic tool to perform 'SRS system self-check' and 'crash sensor zero-point calibration'. Confirm B165E becomes a history code or does not return.
  • 8
    Road test verification: Perform a 20-30 km road test, including bumpy road sections and slight steering. Confirm the airbag fault warning lamp no longer illuminates. Read the data stream to monitor the real-time voltage of the right front crash sensor (normal reference voltage is 2.5V±0.5V).
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Chafed wiring harness on right front side member of BYD S6 causing B165E

✓
A 2015 BYD S6 with 80,000 km on the clock had the airbag warning light staying on. Retrieved fault code B165E-00 (Right front impact sensor short to ground). Inspection revealed the wiring harness clip at the front of the right front frame rail had detached, allowing the harness to chafe against the sharp edge of the rail when the vehicle hit bumps. The damaged insulation caused the signal wire to short to ground. Repair: Cut out the damaged wiring section, soldered the joint and insulated it with heat shrink tubing. Re-secured the harness using corrugated tubing and retaining clips, maintaining at least 20 mm clearance from body metal. Replaced the impact sensor connector (terminals were oxidised). Cleared the fault codes and the system returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Yuan EV sensor connector corroded and shorted after driving through water

✓
2019 BYD Yuan EV. After driving through water, the airbag warning light came on. The scan tool showed DTC B165E. Inspection found the right front impact sensor located low below the headlight; water entered the connector during water wading. Disconnecting the connector revealed severely oxidised pins with verdigris, creating a low-resistance path between the power and ground pins. Repair: Cleaned the connector thoroughly with electronic contact cleaner, replaced the waterproof seal, and re-tinned the sensor pins. Checked the left front sensor on the same circuit and found similar corrosion; repaired both. After repairs, applied waterproof silicone grease to the connectors. Fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM sensor fitted incorrectly following accident repair

✓
2021 Tang DM. Following a front-end collision, a non-authorised repairer replaced the right front longitudinal rail and bumper. One week after the repair, DTC B165E appeared. Inspection found the repairer had not routed the wiring harness to factory specifications during the crash repair; screws trapped the sensor harness between the longitudinal rail bracket and bumper bracket, and prolonged compression damaged the insulation, causing a short to earth. Additionally, the repairer had overtightened the sensor (exceeding 20 N·m), creating micro-cracks in the housing and stressing internal components. Replaced the right front impact sensor, rerouted the wiring per the workshop manual (secured with factory harness clips, avoiding high-temperature and friction areas), and torqued the mounting bolt to 9 N·m.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song MAX SRS ECU internal circuit fault misdiagnosis

✓
2019 Song MAX, no accident history. SRS warning light suddenly illuminated, DTC B165E stored. Visual inspection found wiring harness and sensor appearance normal. Measured sensor resistance and wiring insulation—both normal. Suspected ECU internal fault. Swapped right-front and left-front sensors; DTC B165E (right-front) persisted, confirming the sensor was not at fault. Replaced SRS control unit (under the gear lever, part no. SC-3636100). Programmed and matched the new module; fault cleared. Root cause: short circuit in the constant current source circuit inside the ECU that powers the right-front sensor.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro EV sensor internal component breakdown

✓
2020 BYD Qin Pro EV. Airbag warning light came on suddenly while driving; no collision history. Diagnosed DTC B165E. Measured sensor harness resistance to earth at 0.2 Ω. After disconnecting the sensor connector, harness side resistance to earth measured infinity, confirming an internal short in the sensor. Disassembled the sensor and found the internal piezoelectric ceramic element had absorbed moisture due to seal failure, causing the signal processing circuit power supply to short to earth. Replaced the OEM right front impact sensor (part number 5A-3636100) and waterproofed the harness connector (wrapped with waterproof tape). Fault resolved.
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]