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B16F612

DTC B16F612 indicates a short to vehicle battery positive (B+, usually 12V) in the first signal circuit of an airbag system (SRS) sensor — Qin Plus

Safety System

DTC B16F612 indicates a short to vehicle battery positive (B+, usually 12V) in the first signal circuit of an airbag system (SRS) sensor.

On the BYD Qin PRO, this typically points to the first signal circuit (pressure sensor signal wire or communication wire) of the front passenger Occupant Classification System (OCS) sensor.

During normal operation, this circuit voltage varies between 0-5V.

A short to power pulls the voltage to 12V, preventing the SRS control unit (ACU) from correctly identifying the seat occupancy status.

This fault triggers the safety system protection mechanism, which may disable the passenger-side airbag or seat belt pretensioner, or illuminate the airbag warning lamp continuously.

This creates a risk of the airbag failing to deploy during a collision or deploying unintentionally.

4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Worn under-seat wiring harness: Frequent front seat fore-and-aft movement wears the harness sheath, shorting internal wires to a power wire (such as constant B+ or IGN+).
  • 2Internal sensor short circuit: Internal circuit damage in the seat occupancy sensor (OCS) module shorts the signal terminal to the power supply terminal.
  • 3Connector water ingress and corrosion: Vehicle wading, car washing, or sunroof leaks cause water to enter the under-seat connector, resulting in a short circuit between terminals.
  • 4Accident repair wiring error: After collision repair, the SRS wiring harness is not routed along the standard path, signal and power wires are bundled too tightly, or the insulation is damaged.
  • 5SRS control unit internal fault: Damaged ACU internal sampling circuit incorrectly identifies a normal signal as a short to power (less common, but rule out).
What To Do
  • 1
    Use VDS or a dedicated diagnostic tool to read the complete fault code and freeze frame data. Confirm the fault is on the passenger side (B16F6 usually indicates the passenger side; B16F5 indicates the driver side).
  • 2
    Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge.
  • 3
    Remove the front passenger seat and inspect the under-seat wiring harness, specifically checking the harness sleeve in the seat rail sliding area for wear or splits.
  • 4
    Disconnect the Occupant Classification Sensor (OCS) connector. Use a multimeter to measure the voltage to ground on the first wire on the harness side (usually the signal wire, Pin 1). If the voltage is 12V, this confirms a short to power in the wiring harness. If the voltage is 0V, replace the sensor.
  • 5
    If a wiring harness short circuit is confirmed, progressively strip the harness sheath along the routing path for inspection. Focus on the intersections with the seat motor power wire and the heating pad power wire. Repair any damaged insulation and reroute the wiring.
  • 6
    If the wiring harness is intact, measure the resistance between the OCS sensor terminals to check for an internal short circuit. Replace the seat occupancy sensor assembly if necessary (on some models, replace the seat cushion assembly simultaneously).
  • 7
    After repair, reconnect all connectors and the battery. Use the diagnostic tool to clear the fault code and perform an SRS system self-check. Confirm B16F612 does not return.
  • 8
    Perform static and dynamic tests: simulate a passenger occupying and vacating the seat. Observe the ACU data stream to verify the occupancy status switches normally and confirm the fault is completely eliminated.
Real-World Cases
BYD DTC AI Analysis

Seat rail wear caused wiring harness short circuit in Qin Pro DM

✓
A 2019 BYD Qin Pro DM with 30,000 km had the airbag warning light on constantly. Retrieved DTC B16F612. Inspection found the OCS wiring harness beneath the passenger seat with sheath wear at the frontmost position of the seat rail. The internal purple signal wire and red power wire had worn through their insulation from prolonged friction, causing a short circuit. Repaired the damaged harness, fitted protective sleeving to the signal wire, and adjusted the harness clip positions to avoid interference with the seat rail. Fault resolved.
BYD DTC AI Analysis

OCS connector corroded and shorted after driving through water

✓
2018 Qin PRO petrol. Airbag warning light came on after driving through flood water, logging DTC B16F612. Inspection found water staining inside the OCS connector beneath the passenger seat. Electrolytic corrosion had created a short circuit resistance (~200 Ω) between Pin 1 (signal) and Pin 4 (12 V power) terminals. Repair steps: cleaned the connector thoroughly, flushed with electronic cleaner and dried, applied conductive paste, and reinstalled. Fault cleared. Recommend checking vehicle sealing integrity.
BYD DTC AI Analysis

Wiring harness incorrectly connected after accident repair

✓
Following front collision repairs on a Qin Pro DM, the airbag warning light illuminated upon delivery to the customer. Diagnosis revealed DTC B16F612. Inspection found that when reinstalling the passenger seat, the technician had reversed the OCS harness and seat heater power harness connectors (the two connectors are physically similar but have different pin configurations), causing the signal wire to connect directly to 12V power. The technician corrected the connector connections, confirmed the OCS sensor had not sustained overvoltage damage, cleared the fault codes, and the system returned to normal.
BYD DTC AI Analysis

OCS sensor internal circuit fault

✓
2019 BYD Qin Pro DM, no accident history or water damage. Airbag warning light intermittent; DTC B16F612 often appears during cold starts. Inspected wiring harness, intact. Measured an intermittent short between the OCS sensor signal wire and power terminal when shaking the sensor. Disassembled sensor: sealant on internal pressure sensing element had cracked; moisture ingress shorted the circuit board. Repair: Replaced seat occupancy sensor (requires also replacing seat cushion foam, since the sensor is integrated into the pad). After programming and matching, fault resolved.
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.