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B16FD00

DTC B16FD00 indicates the SRS (airbag system) control module detects a mismatch between the electrical characteristics of a sensor's third wire (typically the sensor identification/configuration wire) and the preset ECU configuration — Seal 6 EV

Safety System

DTC B16FD00 indicates the SRS (airbag system) control module detects a mismatch between the electrical characteristics of a sensor's third wire (typically the sensor identification/configuration wire) and the preset ECU configuration.

In BYD Qin PRO models, this usually involves the ID recognition wire for the seat occupancy sensor (SBR) or seat belt pretensioner sensor.

The third wire transmits the sensor part number, installation position, or calibration parameters to the SRS ECU, typically via a specific resistance value or voltage range.

The ECU logs a configuration error when it detects an open circuit, short circuit, or resistance/voltage outside the calibrated range on this wire.

Causes include installing non-genuine parts, misaligned pins, or resistance drift from wiring harness aging.

Unlike standard short or open circuits, this fault indicates a hardware identity recognition failure.

It can force the SRS into a degraded mode, affecting normal airbag deployment logic.

The B16FD00 fault code on the Seal 6 EV indicates a mismatch between the SRS airbag control module configuration and a sensor’s third-wire identification signal, often linked to the seat occupancy or seat belt pretensioner system. Severity is medium, as airbag deployment logic may be affected. Common causes include a non-OEM seat or seat belt assembly, or damaged under-seat wiring. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Installation of a non-OEM seat assembly or seat belt assembly: The third-wire identification resistance on an aftermarket or used part does not match the factory calibration value, preventing the ECU from identifying the sensor.
  • 2Physical damage to the under-seat wiring harness: Frequent fore/aft seat adjustment on the Qin PRO may cause the third wire (typically a thin-gauge signal wire) to break or develop poor contact at the slide rail, generating abnormal resistance.
  • 3Pin misalignment or backed-out terminal: The third wire terminal failed to seat fully or misaligned when disconnecting or reconnecting the sensor connector during repair, causing the ECU to read an incorrect voltage.
  • 4Water ingress or oxidation: Water entering the under-seat connector during vehicle wading or interior cleaning oxidizes the third wire terminal. This creates additional contact resistance exceeding the ECU detection range.
  • 5SRS software version mismatch: After flashing or upgrading the ECU software, the new software changes the calibration range of the sensor configuration parameters, causing incompatibility with the original vehicle hardware.
What To Do
  • 1
    Use the ED400/ED600 diagnostic tool to read the complete fault information. Confirm if B16FD00 is a current (Active) fault, and record any accompanying SRS fault codes to determine the specific sensor location (driver/passenger seat, left/right).
  • 2
    Visually check the airbag warning light status on the instrument cluster to confirm if the system has entered fault protection mode (the light usually remains on).
  • 3
    Determine the physical location of the faulty sensor based on vehicle configuration (typically the passenger seat occupancy sensor on the Qin PRO). Inspect the yellow SRS connector under the seat (usually containing a short-circuit protection tab) for looseness, water ingress, or corrosion.
  • 4
    Disconnect the battery negative terminal and wait at least 90 seconds to discharge the SRS capacitor residual charge. Unplug the faulty sensor connector and check if the third wire pin (usually the center pin or a specific color wire, such as the green/white wire) is backed out or bent.
  • 5
    Use a multimeter to measure the resistance to ground of the third wire on the sensor side. The third wire of the OEM seat occupancy sensor typically contains a specific identification resistor (such as 2.4kΩ±5%). If the measured value is infinity (open circuit) or 0Ω (short circuit), the internal identification resistor is faulty. Replace the OEM sensor assembly.
  • 6
    Measure the voltage of the third wire on the harness side: Reconnect the battery, turn the ignition switch to ON, and measure the voltage between the third wire of the connector and ground. The normal value is a 5V reference voltage. If the voltage is abnormal, check the continuity of the wiring harness to the SRS ECU and repair any open or short circuits.
  • 7
    Confirm part code: Verify the replacement sensor part number matches the vehicle VIN (sensor codes may differ between Qin PRO DM, petrol versions, and different model years). Use only genuine BYD parts.
  • 8
    Clear the fault code and perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times). Confirm the fault code does not reappear. Finally, perform a seat fore-and-aft sliding test to confirm no wiring harness interference.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro DM: Replaced seats with aftermarket ones, triggering a configuration error.

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After a detail shop installed aftermarket leather seats in a 2018 Qin Pro DM, the airbag warning light came on. The scan tool showed fault code B16FD00 (passenger seat occupant sensor third wire configuration error). Inspection found the replacement seats had no genuine SBR sensor, and the third wire was open. Fix: Installed a genuine seat occupant sensor (part number TF-XXXXX) and connected a 2.4kΩ identification resistor to the sensor’s third wire. Fault cleared.
BYD DTC AI Analysis

Worn seat rails causing intermittent open circuit in the third wire.

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2019 BYD Qin Pro (petrol). Airbag warning light came on intermittently. DTC B16FD00: intermittent fault. Inspection found a poor connection at the third wire (green) under the passenger seat when the seat track was at its forward-most position. Cause: frequent seat adjustment caused the thin wire to fatigue and break at the retaining clip. Repaired the wiring harness, added 20 cm of slack, rerouted it clear of the seat track travel, and replaced the connector terminals. Fault no longer present.
BYD DTC AI Analysis

Connector oxidation after water wading caused identification resistor abnormality.

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After driving through standing water, the dash showed an airbag fault. Scan tool read code B16FD00. Disassembly revealed water inside the SRS connector beneath the passenger seat. The third wire terminal had oxidised and turned black, creating about 500Ω of contact resistance. In series with the factory 2.4kΩ, the total resistance exceeded the ECU’s 2.0–2.8kΩ recognition range. Repair: Thoroughly cleaned the connector, treated the terminals with electronic cleaner, applied conductive grease. Total resistance returned to normal. Cleared fault code, problem resolved.
BYD DTC AI Analysis

Pin misalignment after accident repair caused configuration signal fault.

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A collision-repaired Qin PRO set DTC B16FD00 after replacing the SRS ECU and wiring harness. Inspection found that wire 3 and wire 4 (signal return line) pins in the harness connector were swapped during assembly. The ECU read an incorrect configuration voltage (about 12V instead of the 5V divided value). Fix: Repositioned the pins and verified the wire sequence for lines 1-4 against the workshop manual terminal diagram. Fault cleared.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.