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B16001B

DTC B16001B indicates the SRS (airbag) system detects a range/performance fault in the driver seat occupancy sensor (OCS - Occupant Classification System) signal circuit — Qin Plus

Safety System

DTC B16001B indicates the SRS (airbag) system detects a range/performance fault in the driver seat occupancy sensor (OCS - Occupant Classification System) signal circuit.

Specifically, the ACU (Airbag Control Unit) receives a sensor resistance value outside the calibrated range (typically an open circuit, short circuit, or abnormal resistance), or the signal characteristics fail to match the expected logic.

This film pressure sensor, located inside the driver seat cushion or on the inner side of the seat rail, monitors seat occupancy in real time to determine whether to allow full-power airbag deployment during a collision.

If the system cannot confirm driver presence, it illuminates the airbag warning light and may enter a degraded protection mode (such as disabling airbag deployment or reducing deployment force), posing a severe safety hazard.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD Qin PLUS DM-i loose connection at under-seat connector

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Symptom: After starting, the airbag warning light on the dash stayed on. VDS read DTC B16001B (driver seat occupancy sensor circuit fault). No collision history; clearing the code didn’t help. Diagnosis: Inspected the harness under the driver’s seat. Found the white 2-pin connector for the seat occupancy sensor (mounted on the inner side of the slide rail) wasn’t fully locked. Measured contact resistance between the connector terminals and body harness: 5Ω (normal <1Ω). The loose connection caused intermittent signal interruption. Resolution: Disconnected the negative battery terminal for 3 minutes. Removed the seat bolts, unplugged the sensor connector. Cleaned oxidation off the terminals with electrical contact cleaner. Reconnected the plug, making sure the lock clicked in. Secured the harness to the seat frame with cable ties. Cleared fault codes and test drove 20 km — the fault didn’t come back.
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BYD DTC AI Analysis

BYD Song Pro seat occupancy sensor unit damaged

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Symptoms: The airbag warning light illuminated intermittently, particularly when driving over rough surfaces or during heavy braking, and might extinguish automatically after the vehicle sat idle. A VDS scan revealed DTC B16001B, with historical records showing this fault had occurred 12 times, all intermittent. Diagnosis: Inspected the wiring harness beneath the driver's seat – the harness appeared in good condition and the connector was secure. Removed the driver's seat, stripped back the upholstery and foam, and extracted the film pressure sensor. Measured the sensor's static resistance with a multimeter; the reading showed open circuit (normal range should vary between 500Ω–2kΩ). When gently flexing the sensor wiring, the resistance reading fluctuated occasionally. Determined the internal film circuit had suffered a fatigue fracture due to prolonged compression. Resolution: Replaced the genuine driver seat occupancy sensor assembly (Part No: SC-6980320C). Applied special thermal conductive adhesive between the sensor and seat foam during installation to ensure proper contact, then reassembled the seat. Performed the 'Seat Occupancy Sensor Zero Calibration' procedure using the VDS and cleared the DTC. A one-month follow-up confirmed the fault had not returned.
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BYD DTC AI Analysis

BYD Han EV: Seat modification caused wiring harness open circuit

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Symptoms: The owner fitted racing bucket seats, and the instrument cluster immediately displayed 'Check Airbag System'. Retrieved fault codes B16001B and B16001C (passenger side). After refitting the original seats, the passenger side fault cleared, but the driver side B16001B remained. Diagnosis: The modification involved forcibly removing the original seat occupancy sensor and overstretching its wiring harness (the transition section from seat to body harness). Stripping back the harness insulation revealed two copper wires completely severed, with only the outer sheath intact. Measured an open circuit between the sensor and the ACU. Resolution: Replaced the complete seat harness assembly (including the occupancy sensor connector) as the break was at the junction of the seat harness and body harness. Re-routed the wiring to specification, leaving at least 10 cm of slack for seat travel. Installed the original seats, cleared fault codes with a scan tool, and ran a system self-test. Fault resolved. Recommendation: If modifying the seats, use an adapter harness that incorporates the occupancy sensor interface.
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BYD DTC AI Analysis

Third-party seat cushion causing signal interference in BYD Dolphin

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Symptoms: After 8 months of use, the airbag warning light came on with intermittent fault code B16001B. The dealership cleared the code, but it returned after 2–3 days of driving with no specific trigger pattern. Diagnosis: Inspected the seat occupancy sensor and wiring harness—both normal. Further inquiry revealed the owner had recently fitted a third-party smart seat cushion with heating and ventilation. Found the cushion's power harness (12V to 5V adapter) routed parallel and tied together with the seat occupancy sensor harness. Disconnected the cushion, road-tested the vehicle for 3 days, and the fault did not recur. Reconnected the cushion and the fault returned within 1 day, confirming electromagnetic interference was distorting the sensor signal. Resolution: Removed the third-party cushion and restored the seat to original condition. Re-routed the under-seat wiring, separating the sensor signal wires from all power lines (including seat heating, ventilation, or aftermarket devices) by at least 15 cm. Wrapped the sensor harness with aluminium foil shielding tape. Cleared the fault code, issue resolved.
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BYD DTC AI Analysis

BYD Tang DM-i airbag control unit software calibration error

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**Symptoms:** Within one week of taking delivery of the new vehicle, the instrument cluster occasionally displayed the airbag warning light, with DTC B16001B stored. The vehicle had no modifications and the seat showed no abnormalities. The fault appeared more often on cold starts and sometimes disappeared after warm-up. **Diagnosis:** Inspected the seat occupancy sensor hardware connections and found them normal; measured resistance values were within specification. Read live data with VDS and found the ACU (Airbag Control Unit) consistently showed the driver seat status as 'Empty', even when occupied, indicating the ACU could not correctly recognize the sensor signal. Consulted BYD Technical Service Bulletin TSB-2023-08 and confirmed that some vehicles from this batch had an ACU software calibration defect causing incorrect recognition of the signal thresholds for a specific sensor batch. **Resolution:** Connected the vehicle to the BYD after-sales server and upgraded the Airbag Control Unit (ACU) software to the latest version (from V2.1.2 to V2.3.5). After the upgrade, performed the 'Seat Occupancy Sensor Sensitivity Learning' procedure (simulating both occupied and unoccupied states). Cleared stored fault codes and tested 10 cold starts; the fault was completely eliminated.
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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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.