AU
B16471B

DTC B16471B indicates the driver-side seatbelt pretensioner circuit resistance exceeds the normal threshold set by the SRS control module (typical normal range: 1 — Qin Plus

Safety System

DTC B16471B indicates the driver-side seatbelt pretensioner circuit resistance exceeds the normal threshold set by the SRS control module (typical normal range: 1.5-4.0 Ω; detected value is high).

The pretensioner is a pyrotechnic component of the passive safety system, containing a resistance wire and an igniter charge.

Excessive resistance indicates high circuit impedance resulting from poor contact, wiring harness oxidation, connector corrosion, or pretensioner aging.

This fault forces the SRS system into a degraded mode and continuously illuminates the airbag warning light.

During a collision, the driver-side seatbelt pretensioner may fail to deploy and retract, severely compromising occupant restraint protection.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Loose connections, backed-out terminals, or oxidized pins at the yellow pretensioner connector under the driver's seat (usually marked D+, D-) cause increased contact resistance. This is the most common cause, especially after frequent fore-and-aft seat adjustment or driving through water.
  • 2Internal slip ring wear in the clock spring (spiral cable) or poor contact in the ribbon cable causes unstable or excessively high resistance in the pretensioner signal circuit.
  • 3Aging, breakage, or moisture corrosion of the internal resistance wire in the seat belt pretensioner causes the resistance to exceed the tolerance range (typically 5-10Ω or higher).
  • 4Floor wiring harness worn or broken near the seat track and reconnected, or modifications (such as adding seat heating/ventilation) introducing series resistance into the circuit.
  • 5Internal fault in the SRS control module sampling circuit or software calibration drift causing the module to misjudge a normal resistance value as abnormal (compare left and right side resistance values to verify).
What To Do
  • 1
    Safety Preparation: Disconnect the 12V battery negative terminal. Wait at least 3 minutes for the SRS capacitor to discharge. Disable the airbag system. Wear an anti-static wrist strap.
  • 2
    Visual inspection: Verify the yellow SRS connector under the driver's seat is fully locked, inspect the pins for green corrosion, burn marks, or backed-out pins, and check the wiring harness for wear at the seat slide rail.
  • 3
    Resistance measurement: Disconnect the pretensioner connector. Use a digital multimeter (Fluke or similar low-current meter) to measure the resistance between the pretensioner terminals. Normal resistance is 2.0-3.0 Ω. A reading greater than 4.5 Ω indicates a faulty pretensioner.
  • 4
    Harness continuity test: Measure harness continuity between the pretensioner connector and the SRS ECU (usually located under the center console or front compartment). Focus on checking continuity at each clock spring pin (if the pretensioner connects via the clock spring).
  • 5
    Cleaning and repair: If oxidation is present, clean the pins with electrical contact cleaner, apply conductive grease, and verify the connector locking tab is intact. If the wiring harness is damaged, repair it using the dedicated yellow high-temperature wiring harness. Do not use simple twisted joints.
  • 6
    Component Replacement: If the pretensioner unit resistance is abnormal, replace the driver seat belt assembly (including the pretensioner). After replacement, use a dedicated diagnostic tool (such as BYD VDS or Launch X431) to perform 'Airbag Configuration' and 'Resistance Learning'.
  • 7
    System verification: Clear the fault code. Turn the ignition switch to ON and verify the SRS warning lamp turns off after the self-check. Use the diagnostic tool to read the data stream and confirm the pretensioner resistance is within the normal range. Perform a simulated crash test (if supported by the equipment).
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

The connector under the seat oxidized, causing resistance drift.

✓
The vehicle came in with the airbag warning light on. Read DTC B16471B. Found the yellow connector under the driver's seat showed water damage, with oxidised and blackened pins. Cleaned it with WD-40 Precision Electrical Contact Cleaner, reducing resistance from 5.2Ω to 2.3Ω. Fault resolved. Advised the customer to avoid spraying water directly under the seats when washing the car and to waterproof the connector.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal open circuit in clock spring causes false alarm.

✓
BYD Qin Pro DM. Customer reported the airbag warning light illuminating intermittently. Pretensioner resistance measured normal. Resistance from the clock spring to the SRS ECU was unstable, fluctuating between 2–8 Ω. Disassembled the steering wheel and found a broken internal ribbon cable in the clock spring. Replaced the clock spring; resistance stabilised at 2.1 Ω. Cleared fault codes; the fault has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

Aftermarket seat heater installation caused abnormal circuit resistance.

✓
Owner installed seat heating pads, splicing into the wiring to connect power. During the work, the owner accidentally damaged the pretensioner harness insulation, causing the copper wires to oxidise. Inspection found extra resistance spliced into the pretensioner circuit. Repaired the wiring (replaced the entire section of yellow SRS-specific cable) and removed the illegal heating pad wiring. Resistance measurements returned to normal and the SRS system resumed normal operation.
BYD DTC AI AnalysisFrom Chinese market (translated)

Pretensioner internal resistance high due to aging

✓
2018 Qin Pro, 5 years old. DTC B16471B wouldn't clear. Disconnected the pretensioner plug and measured the pretensioner's resistance directly: 6.8Ω, well above spec. Diagnosed an aged pyrotechnic resistor wire inside the pretensioner. Replaced the driver-side seat belt assembly (including pretensioner). Performed the 'Replace Pretensioner' configuration with VDS2000. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS control module software misdiagnosis

✓
No accident history. Measured resistances of the pre-tensioner and harness were both within the normal range (2.4Ω), but code B16471B appeared frequently. Compared to the passenger side resistance (2.2Ω), the difference was minimal. Upgraded the SRS control module software to the latest version (2023 patch); the fault code did not return. Determined to be a false trigger caused by overly sensitive calibration in the early software.
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.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]