AU
B16FF12

DTC B16FF12 indicates a short to the vehicle 12V power supply on the fourth circuit (typically the signal or CAN communication line) of an SRS (airbag system) crash sensor (such as the front crash sensor, side crash sensor, or seat occupancy sensor) — Qin Plus

Safety System

DTC B16FF12 indicates a short to the vehicle 12V power supply on the fourth circuit (typically the signal or CAN communication line) of an SRS (airbag system) crash sensor (such as the front crash sensor, side crash sensor, or seat occupancy sensor).

In the BYD Qin PRO 4-wire sensor architecture, the fourth wire typically transmits sensor signals or diagnostic communications.

When this circuit shorts to power, the SRS control unit (ACM) detects an abnormal voltage (continuous high level) and fails to receive the sensor acceleration signal correctly.

This triggers the safety protection mechanism, forces the airbag system into fail-safe mode (system disabled), and illuminates the instrument cluster airbag warning lamp.

This fault may prevent proper airbag deployment during a collision, posing a severe safety hazard.

The B16FF12 fault code on the Qin Plus indicates a short to the 12V power supply in the fourth circuit of an SRS crash or occupancy sensor. This is a high-severity airbag system fault that can disable proper airbag operation. Common causes include damaged wiring insulation or water/corrosion in the sensor connector. 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 — Qin Plus
  • 1Wiring harness mechanical damage: Long-term vibration and friction against sharp edges damage the wiring harness insulation in the engine compartment or doors, causing the fourth wire to contact and short to a power wire (such as a constant 12V wire). This commonly occurs where harnesses pass through the firewall or hinges.
  • 2Connector water ingress and corrosion: Water fording or poor sealing allows water to enter the sensor connector (usually located inside the front bumper or below the B-pillar). This causes an electrolytic short circuit between the pins, specifically creating a conductive path between the fourth wire and the power supply pin.
  • 3Internal sensor fault: Electrical breakdown of the signal processing chip or filter capacitor on the collision sensor internal PCB shorts the signal output terminal (wire 4) to the internal power supply terminal.
  • 4Improper repair work: During accident repairs or aftermarket equipment installation (such as dash cams or radar), mistakenly connecting the SRS sensor wiring harness in parallel with the power supply wire, or retaining clips piercing the wiring harness insulation.
  • 5External electromagnetic interference damage: Although rare, extreme high-power electromagnetic interference can damage the sensor internal circuit, causing the output stage to short to the power supply.
What To Do
  • 1
    Safety Preparation: Use the BYD VDS2000 or a dedicated diagnostic tool to read the fault code. Confirm B16FF12 is a current fault and the freeze frame data shows the vehicle status at the time of the fault. Disconnect the 12V battery negative terminal and wait at least 3 minutes to allow the SRS control unit capacitor to fully discharge for safe repair.
  • 2
    Locate the faulty sensor: Refer to the Qin PRO workshop manual wiring diagram and determine the specific sensor location (front left/front right crash sensor, side airbag sensor, or seat occupancy sensor) based on the DTC sub-code. Confirm the function of the fourth wire (usually the signal wire or CAN-L).
  • 3
    Sectional isolation test: Disconnect the sensor connector. Use a multimeter to measure the voltage between the fourth wire on the harness side and body ground. A 12V reading confirms the harness is shorted to power. Measure the resistance between the fourth wire on the sensor side and the power pin. Continuity indicates an internal sensor short circuit.
  • 4
    Wiring harness inspection and repair: Trace the sensor wiring harness, focusing on the firewall pass-through, harness retaining clips, and crossover points with the front compartment harness. If damaged, strip the harness, separate the shorted wires, and insulate them with heat-shrink tubing or electrical tape. Replace the entire harness section if necessary.
  • 5
    Connector handling: Inspect connector pins for oxidation, deformation, or water marks. Clean with electrical contact cleaner, apply conductive grease, and replace the connector assembly if necessary. Verify the waterproof sealing ring is intact.
  • 6
    Sensor replacement: If testing confirms an internal short circuit, replace with an OEM collision sensor (Note: some models require sensor coding or height calibration).
  • 7
    System verification: Restore all connections, connect the battery, and turn on the ignition. Use the diagnostic tool to clear the fault code. Perform the SRS system self-test (may include sensor communication testing and crash signal simulation). Confirm B16FF12 does not return and the instrument warning light turns off.
Real-World Cases
BYD DTC AI Analysis

A worn front bumper wiring harness on a Qin Pro DM caused a short circuit.

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A 2019 Qin PRO DM with 30,000 km had the airbag warning light on the dash stay on constantly. Scanning revealed DTC B16FF12 (Right front impact sensor Line 4 short to power). The wiring harness retaining clip inside the right front wheel arch had come loose, allowing the harness to chafe against the edge of the engine mount bracket. The insulation wore through, and the Line 4 signal wire contacted the 12V power wire. Repairing the wiring and re-securing the harness cleared the fault.
BYD DTC AI Analysis

Sensor connector shorted due to water ingress during wading

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2018 BYD Qin Pro (petrol). Airbag warning light came on after driving through heavy rain and flood water, logging DTC B16FF12. Diagnosis found water ingress in the left front impact sensor connector (inside the left front chassis rail). Electrolyte formed between the pins, shorting the fourth wire to the power pin. Cleaned and blow-dried the connector, applied waterproof silicone grease, and replaced the seal ring – fault resolved. Check the wading depth sensor for watertightness.
BYD DTC AI Analysis

Wiring harness pinched during accident repair, causing short circuit

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A 2019 BYD Qin Pro developed DTC B16FF12 following accident repairs. Inspection found the wiring loom incorrectly trapped between the metal bracket and front bumper during the repair, crushing the insulation on the fourth wire and causing a short to the bracket (indirectly energised via a modified LED light wire). Rerouted the wiring loom away from the pinch point. Fault cleared.
BYD DTC AI Analysis

Internal PCB failure in the sensor

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2019 Qin Pro DM. Recurring B16FF12 DTC. Checked wiring harness, no abnormality found. Measured between pin 4 of the sensor connector and the power supply terminal; found internal short. Replaced left front impact sensor, fault resolved. Diagnosed as internal signal processing chip breakdown, likely due to early batch component defect or voltage surge.
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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.