AU
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 — Qin Plus

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.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Non-OEM seat or seat belt assembly installed: The third-wire identification resistor in an aftermarket or salvaged part does not match the OEM calibration value, preventing the ECU from identifying the sensor.
  • 2Physical damage to the wiring harness under the seat: Frequent fore-and-aft seat adjustment on the Qin PRO can break the third wire (usually a small-gauge signal wire) or cause poor contact at the seat track, creating abnormal resistance.
  • 3Pin misalignment or backed-out terminal: Disconnecting or reconnecting the sensor connector during repairs left the third wire terminal misaligned or not fully seated, causing the ECU to read an incorrect voltage.
  • 4Water ingress or oxidation: Vehicle wading or interior cleaning causes water to enter the under-seat connector. This oxidizes the third wire terminal, generating additional contact resistance that exceeds the ECU recognition range.
  • 5SRS software version mismatch: After flashing or upgrading the ECU software, the new software changes the calibration range for 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. Verify if B16FD00 is a current (Active) fault and record any accompanying SRS fault codes to determine the exact sensor location (driver/passenger seat, left/right).
  • 2
    Visually inspect the instrument cluster airbag warning light status to confirm whether the system has entered fault protection mode (typically remains illuminated).
  • 3
    Determine the physical location of the faulty sensor based on vehicle configuration (for the Qin PRO, this is typically the passenger seat occupancy sensor). 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 residual charge in the SRS capacitor. Unplug the faulty sensor connector and check if the third wire terminal (usually the center pin or a specific color wire, such as green/white) 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 (e.g., 2.4kΩ±5%). If the measured value is infinite (open circuit) or 0Ω (short circuit), the sensor's internal identification resistor is faulty. Replace the OEM sensor assembly.
  • 6
    Measure harness-side third wire voltage: Reconnect the battery, turn the ignition switch to ON, and measure the voltage between the connector's third wire and ground. The normal value is a 5V reference voltage. If the voltage is abnormal, check harness continuity to the SRS ECU and repair any open or short circuits.
  • 7
    Confirm part number: Verify the replacement sensor part number matches the vehicle VIN (sensor part numbers may differ between Qin PRO DM, fuel versions, and different model years). Use only genuine BYD parts.
  • 8
    Clear the fault code and perform the SRS system self-check cycle (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.

✓
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.

✓
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.

✓
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.

✓
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 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.