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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 — Seal U

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.

The B16F612 fault code on the Seal U indicates a high-severity short to battery positive in the first signal circuit of an SRS airbag/seat occupancy sensor. This can prevent correct passenger seat detection and may disable airbag or pretensioner functions or keep the airbag warning light on. Common causes include worn under-seat wiring or an internal OCS sensor fault. 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 U
  • 1Under-seat wiring harness wear: Frequent forward and backward movement of the front seat wears the harness sleeve, shorting internal wires to power wires (such as constant B+ or IGN+).
  • 2Sensor internal 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.
  • 4Collision repair wiring error: After collision repair, the SRS wiring harness deviates from the standard routing path, signal wires are bundled too tightly with power wires, or the insulation is damaged.
  • 5SRS control unit internal fault: A damaged ACU internal sampling circuit misinterprets 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 occurred on the passenger side (B16F6 usually corresponds to the passenger side; B16F5 usually corresponds to 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 wiring harness under the seat. Specifically check the harness sleeve in the seat rail sliding area for wear or cuts.
  • 4
    Disconnect the Occupant Classification Sensor (OCS) connector. Use a multimeter to measure the voltage to ground of the first wire on the harness side (usually signal wire Pin 1). If the voltage is 12V, confirm a short to power in the wiring harness. If the voltage is 0V, replace the sensor.
  • 5
    If inspection confirms a wiring harness short circuit, progressively open the harness sleeve along the routing to inspect. Focus on crossover points 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 (some models require replacing the seat cushion assembly simultaneously).
  • 7
    After repair, reconnect all connectors and the battery. Use the diagnostic tool to clear the fault code, perform an SRS system self-check, and confirm B16F612 does not return.
  • 8
    Perform static and dynamic tests: simulate a passenger occupying and leaving the seat, observe the ACU data stream to verify the occupancy status switches normally, and confirm the fault is completely resolved.
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 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.