AU
B165D-00

DTC B165D-00 indicates a communication link interruption between the Supplemental Restraint System (SRS) Electronic Control Unit (ECU) and the Right Front Frontal Impact Sensor (RFFIS) — Seal U

Safety System

DTC B165D-00 indicates a communication link interruption between the Supplemental Restraint System (SRS) Electronic Control Unit (ECU) and the Right Front Frontal Impact Sensor (RFFIS).

In BYD vehicle architectures, this sensor typically features a 2-wire (signal loop) or 3-wire (power/signal/ground) design.

It communicates via a hard-wired connection through the SRS ECU G10 connector, specifically the G10-3 signal terminal and G10-14 return terminal.

The ECU sets this DTC if it detects the sensor circuit resistance exceeds the threshold (open circuit >10kΩ or short circuit <200Ω) during a monitoring cycle, or if it receives no valid sensor data for 3 consecutive monitoring cycles.

This fault forces the SRS into a degraded mode, disabling the right-side frontal collision detection function.

During a frontal impact, the system may delay or fail to deploy the right front airbag and right-side seat belt pretensioner.

The instrument cluster SRS warning light remains illuminated to indicate a system fault.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Sensor electrical connector loose, terminal backed out, or poor contact: Commonly results from failing to fully engage the connector locking tab after front bumper repairs, headlamp replacement, or accident repairs, or from prolonged driving on rough roads causing vibration to loosen the connector.
  • 2Wiring harness open circuit or damaged insulation: Panel adhesive covered the wiring harness in the front longitudinal beam area during accident repairs, sharp edges cut the harness, or long-term bending broke the internal copper wires; rodents chewed the harness insulation, causing a hidden short circuit.
  • 3Connector corrosion and oxidation: Driving through water, directly spraying the motor compartment with a high-pressure washer, or aging sealing rings allow rainwater to enter the sensor connector, causing copper corrosion on the terminals and increased contact resistance (>5Ω).
  • 4Internal sensor body fault: The internal piezoelectric element or diagnostic resistor (typically 2.0-2.4kΩ) failed, preventing valid signal generation despite a normal physical connection.
  • 5Abnormal SRS ECU connector terminals: Terminal 3 or 14 of connector G10 has a spread terminal, backed-out pin, or oxidation, causing poor contact with the wiring harness. Wiggling the wiring harness triggers the fault intermittently.
What To Do
  • 1
    Safe power down: Turn off the ignition switch, disconnect the 12V battery negative cable, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.
  • 2
    Locate the component: Open the hood, remove the right front wheel arch liner or front bumper upper cover, and find the right front crash sensor on the right side of the radiator frame or behind the right front headlight.
  • 3
    Visual inspection: Check that the sensor connector is fully inserted and locked with a 'click'. Inspect the connector housing for cracks and verify the sealing ring is present. Inspect the wiring harness within 20 cm for damage, burns, or pinch marks.
  • 4
    Sensor body test: Disconnect the connector. Use a digital multimeter to measure the resistance between the two sensor terminals. Standard value: 2.0-2.4 kΩ (at 20°C). If the resistance is 0 Ω (short circuit) or infinite (open circuit), replace the sensor.
  • 5
    Harness continuity test: Disconnect the SRS ECU G10 connector. Measure the resistance from the sensor harness connector to G10-3 (signal wire) and to G10-14 (return wire). Resistance must be less than 1.0 Ω. If resistance is too high, repair the open circuit.
  • 6
    Harness insulation test: Measure the insulation resistance from both sensor harness terminals to body ground and to the power supply. The resistance must be greater than 10 MΩ. If the resistance is low, locate the damaged point on the harness and wrap it with tape, or replace the harness assembly.
  • 7
    ECU terminal inspection: Check terminals 3 and 14 of connector G10 for oxidation or deformation. If necessary, use the dedicated terminal repair tool to adjust the terminals or replace the connector.
  • 8
    Repair and restoration: Clean corroded terminals (using electrical contact cleaner + non-woven cloth). Apply an appropriate amount of conductive paste (not insulating silicone grease). Reconnect all connectors and verify the double-locking mechanisms are fully engaged. Secure the wiring harness with cable ties to prevent chafing against metal edges.
  • 9
    System initialization: Reconnect the battery and turn the ignition switch to the ON position. Verify the SRS warning light on the instrument panel turns off after 6 seconds. Use the diagnostic tool to read the fault codes and confirm B165D-00 changes to a history code or clears.
  • 10
    Final verification: After clearing the fault code, perform a road test (including bumpy roads) or manually shake the wiring harness to simulate vibration. Confirm the fault does not recur and verify the SRS system has no current fault codes stored.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD S6 sensor wiring open circuit after front bumper painting

✓
Symptoms: The airbag warning light on the instrument cluster stayed on. The diagnostic tool retrieved active fault code B165D-00. Repair history showed the front bumper had been repainted one week earlier. Diagnosis: Inspection found the right front crash sensor connector had come loose. Continuity check between G10-3 terminal and the sensor measured infinite resistance. Tracing the harness revealed it was covered with seam sealer near the front frame rail; the copper conductors inside had corroded and fractured. Resolution: Removed the seam sealer, soldered the broken wiring, rewrapped with waterproof tape, and reconnected the plug. Fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin connector corroded after driving through water

✓
Symptoms: The airbag warning light came on suddenly upon starting after an overnight park. No collision history, but the owner recalled driving through deep water a few days earlier. Diagnostic procedure: Retrieved DTCs B165D-00 and B165E-00 (short to ground) alternating. Opened the bonnet and inspected the right-front sensor. Found significant water traces and green copper corrosion inside the connector housing, with oxidised terminal pins. Measured insulation resistance and found a short to ground on the signal wire. Repair: Thoroughly cleaned the connector and sensor terminals using electronic contact cleaner, dried them with compressed air, applied waterproof sealant to the sealing ring to improve sealing, and reassembled. The fault cleared after reconnecting. Advised the owner to avoid driving through deep water.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Atto 3 new vehicle sensor wiring harness loose connection

✓
Symptoms: Three months after delivery, the instrument cluster intermittently displayed an SRS warning. Initially, the warning cleared after switching the ignition off and back on, but gradually became more frequent, occurring two to three times a week. Diagnosis: The warning light was off when the vehicle arrived at the workshop, but the stored history showed DTC B165D-00. Inspection of the right front sensor mounting location found slight deformation of the bracket, which stressed the wiring harness. Wiggling the harness reproduced the fault. Resistance measurements between terminal G10-3 and the sensor fluctuated between 0.5Ω and 5Ω, indicating poor internal contact in the harness. Resolution: Replaced the right front impact sensor wiring harness assembly, adjusted the sensor bracket to relieve stress, added foam wrap around the connector for vibration damping, confirmed SRS system configuration, and delivered the vehicle. Follow-up after one month showed no recurrence.
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]