AU
B16F612

DTC B16F612 indicates a short to vehicle battery positive (B+, usually 12V) in the first signal circuit of an airbag system (SRS) sensor — Atto 8

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 Atto 8 indicates a short to battery positive in the first signal circuit of an airbag/SRS sensor, often linked to the front passenger occupant classification sensor. Severity is high because it can affect airbag or seat belt pretensioner operation. Common causes include worn under-seat wiring or an internal sensor short. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Under-seat wiring harness wear: Frequent forward and backward movement of the front seat chafes the harness sleeve, shorting the internal wires to a power wire (such as constant B+ or IGN+).
  • 2Internal sensor short circuit: A damaged internal circuit 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 a sunroof leak allows water into the under-seat connector, causing a short circuit between terminals.
  • 4Accident repair wiring error: After collision repairs, the SRS wiring harness deviates from the standard path, the signal and power wires are bundled too tightly, or the insulation is damaged.
  • 5SRS control unit internal fault: Damaged ACU internal sampling circuit misinterprets a normal signal as a short to power supply (less common, but rule this 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 to ensure the SRS capacitor fully discharges.
  • 3
    Remove the front passenger seat and inspect the wiring harness under the seat. Specifically check the harness sleeve in the rail sliding area for wear or cuts.
  • 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, the harness is shorted to power. If the voltage is 0V, replace the sensor.
  • 5
    If a short circuit in the wiring harness is confirmed, progressively strip back the harness sleeve along the routing and inspect. Focus on crossing 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. If necessary, replace the seat occupancy sensor assembly (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, perform an SRS system self-check, and verify 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 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 Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.