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B16F811

DTC B16F811 indicates an unintended electrical connection (short circuit) between body ground and the second circuit of a Supplemental Restraint System (SRS) sensor, typically the low-side drive line or signal return line — Qin Plus

Safety System

DTC B16F811 indicates an unintended electrical connection (short circuit) between body ground and the second circuit of a Supplemental Restraint System (SRS) sensor, typically the low-side drive line or signal return line.

In BYD’s SRS architecture, this usually indicates a wiring fault in the seat belt pretensioner igniter, side impact sensor, or seat occupancy recognition sensor.

The SRS control unit detects an abnormally low circuit resistance (approaching 0Ω) and triggers the safety protection mechanism.

This disables airbag and pretensioner deployment to prevent injury from accidental activation.

This constitutes a hard fault, indicating a very high probability of physical wiring damage or an internal component short circuit.

The B16F811 fault code on the Qin Plus indicates a high-severity SRS short circuit to body ground, usually in a seat belt pretensioner, side impact sensor, or seat occupancy sensor circuit. This can disable airbag or pretensioner deployment for safety. Common causes include a shorted pretensioner igniter or damaged wiring insulation near seat rails, the B-pillar, or carpet. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Seat belt pretensioner squib internal short circuit (failure to replace component after a collision, or component aging causing internal bridge wire to blow or short to ground)
  • 2Damaged wiring harness insulation causing a short circuit to body metal (commonly due to harness chafing at the seat rails, B-pillar trim panel, or under the carpet).
  • 3Internal driver MOSFET or monitoring circuit fault in the SRS control unit (especially control units repaired instead of replaced in accident-repaired vehicles)
  • 4Connector water ingress, corrosion, or pin misalignment causing the signal wire to short to ground (common after water wading or car washing).
  • 5Tool or screw pierced the wiring harness during repair, causing a hidden short circuit (incorrect routing during accident repair caused the seat rail to pinch the wiring harness).
What To Do
  • 1
    Use a BYD dedicated diagnostic tool (VDS6000 or ED400) to read all DTCs. Check for accompanying DTC B16F511 (Line 1 fault) or other related fault codes. Record freeze frame data to determine the fault location (driver/passenger seat belt pretensioner, left/right crash sensor).
  • 2
    Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 3
    Check the target sensor connector (usually located near the seat belt buckle or below the B-pillar) for looseness, corrosion, or water ingress. Visually inspect the wiring harness for obvious damage.
  • 4
    Disconnect the SRS control unit. Use a multimeter to measure the resistance to ground of the second wire from the control unit to the sensor (usually the wire with the smaller terminal number). Normal resistance is greater than 1 MΩ. A reading close to 0 Ω confirms a short to ground.
  • 5
    Inspect the wiring harness in sections: Check the harness routing step by step from the sensor end to the control unit end. Focus on wear-prone areas such as seat rails, door sill trim panels, and B-pillars. Repair damaged insulation or replace the wiring harness.
  • 6
    If the wiring is normal, measure the sensor resistance (normal seat belt pretensioner resistance is approximately 2-3Ω; the crash sensor has a specific resistance range). If the resistance is abnormal, replace the sensor assembly.
  • 7
    If the wiring and sensor are normal but the fault persists, this indicates an internal drive circuit fault in the SRS control unit. Replace the control unit and perform vehicle configuration (VIN writing and sensor matching).
  • 8
    Reconnect the battery, clear the fault code, and perform an SRS system self-check cycle. Verify the fault code does not return and the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

2021 BYD Qin Pro petrol: Airbag fault after collision repair

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Symptoms: The vehicle had been repaired following a collision. The dashboard displayed an 'airbag fault' warning light. A scan tool retrieved DTCs B16F511 (sensor line 1 short to ground) and B16F811 (sensor line 2 short to ground). The driver and passenger airbags had been replaced, the SRS ECU had been repaired, and both front seat belts had been replaced, but the fault codes could not be cleared. Diagnosis: The technician inspected the relevant wiring and found no issues. According to the DTC definitions, B16F511 and B16F811 indicate a seatbelt sensor or SRS wiring fault. After ruling out external wiring and connector issues, the technician diagnosed an internal fault in the SRS control unit. Resolution: Replace or repair the SRS control unit (airbag ECU), then reprogram it and clear the fault codes.
Original source ↗
BYD DTC AI Analysis

BYD multiple models seat belt pretensioner sensor wiring fault

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Symptoms: Airbag warning light came on. Retrieved DTCs showed B16F811 (sensor line 2 short to earth), with some vehicles also logging B16F511 (sensor line 1 short to earth) simultaneously. Diagnosis: Checked seatbelt pretensioner connector for loose connections or corrosion; measured sensor circuit resistance to earth and confirmed a short; checked SRS control unit power supply and earth connections; investigated whether the vehicle had been in a collision or submerged. Resolution: Repaired or replaced the damaged wiring harness. If the harness tested normal, replaced the seatbelt pretensioner assembly. If both were normal, replaced the SRS airbag control unit.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro/Song Pro rear seat belt sensor fault (accident vehicle)

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Symptoms After accident repairs, the dash continuously displays airbag system faults. DTC B16F811 cannot be cleared, accompanied by seatbelt pretensioner-related fault codes. Diagnosis Used a factory scan tool to read complete fault data. Inspected the seatbelt pretensioner connectors and found pin retraction or poor contact in some vehicles. Measured pretensioner resistance; normal value is approximately 2–3 Ω. Checked the SRS control unit software version and data integrity. Resolution For repaired airbag control modules, reflash the data or replace the unit. Replace damaged seatbelt pretensioners. Repair any short circuits in the wiring harness, then perform system configuration and calibration.
Original source ↗
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus overview →
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.