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 — Seal U

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 — Seal U
  • 1Installation of a non-genuine seat assembly or seat belt assembly: The third-wire identification resistance of an aftermarket or salvaged part does not match the original factory calibration value, preventing the ECU from identifying the sensor.
  • 2Physical damage to the under-seat wiring harness: Frequent fore-aft adjustment of the Qin PRO seat may cause the third wire (typically a small-gauge signal wire) to break or develop poor contact at the seat track, creating abnormal resistance.
  • 3Pin misalignment or backed-out terminal: The third wire pin failed to seat fully or misaligned with other pins when plugging or unplugging the sensor connector during repair, causing the ECU to read an incorrect voltage.
  • 4Water ingress or oxidation: Driving through water or cleaning the interior introduces water into the connector under the seat. 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 alters the sensor configuration parameter calibration range, 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 fault (Active) and record any accompanying SRS fault codes to determine the specific sensor location (driver/passenger seat, left/right).
  • 2
    Visually inspect the instrument panel airbag warning light status to confirm if the system has entered fault protection mode (typically illuminated solid).
  • 3
    Determine the physical location of the faulty sensor based on vehicle configuration (usually the passenger seat occupancy sensor on the Qin PRO). Inspect the yellow SRS connector under the seat (typically equipped with 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. Disconnect the faulty sensor connector and check if the third wire pin (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 internal identification resistor is damaged. 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 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, petrol versions, and different model years). Use only genuine BYD parts.
  • 8
    Clear the fault code and perform an 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 there is 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.

✓
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 U Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.