AU
B110F

DTC B110F indicates an actuator circuit failure in the solenoid valve (switching valve) inside the PM2 — Atto 3

Thermal Management System

DTC B110F indicates an actuator circuit failure in the solenoid valve (switching valve) inside the PM2.5 air quality detection module.

This solenoid valve controls the physical switching of the sampling air passage to select the channel for in-cabin or outside air sampling.

The air conditioning controller (ACU) triggers this code if it issues a switching command but fails to detect the solenoid valve current feedback or position confirmation signal (such as Hall sensor feedback), or if it detects a coil short or open circuit.

This failure prevents the system from accurately comparing the PM2.5 concentration difference between the cabin and outside air, disables Auto Clean mode, and may force the air conditioning system into a protective recirculation mode.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Solenoid valve coil burnt out or open circuit: Long-term use or voltage fluctuations cause abnormal coil resistance (standard resistance is typically 20-60Ω; a deviation exceeding ±10% indicates failure).
  • 2Valve core mechanically stuck: Dust, fibers, or oil accumulate in the PM2.5 sampling passage, causing the solenoid valve armature to stick or fail to return during operation. The resulting abnormal current draw triggers the diagnosis.
  • 3Wiring harness and connector fault: Wear at wiring harness bends inside the dashboard, oxidized or backed-out terminals, or high temperatures in the HVAC housing deforming the connector and causing an intermittent open circuit.
  • 4Drive circuit fault: Overcurrent damage to the solenoid valve driver chip (usually an H-bridge driver IC) inside the air conditioning controller prevents PWM control signal output.
  • 5Internal air leak in the sensor assembly: Solenoid valve seal aging causes air passage cross-leakage. The pressure sensor detects an abnormal pressure differential and reports a solenoid valve functional failure.
What To Do
  • 1
    Use the VDS1000 or Launch X431 diagnostic tool to read the complete DTCs, confirm whether the fault is current (Present) or history (History), and record the ambient temperature and air conditioning operating conditions from the freeze frame data.
  • 2
    Remove the front passenger glove box or PM2.5 sensor module cover (depending on configuration; on the Song MAX, it is usually located above the blower or on the side of the HVAC housing). Visually inspect the solenoid valve wiring harness connector for burning or water ingress.
  • 3
    Disconnect the solenoid valve connector and use a multimeter to measure the coil resistance. Normal range: 15-80Ω (refer to the repair manual for the standard value). If the reading shows OL (open circuit) or 0Ω (short circuit), replace the PM2.5 sensor assembly (the solenoid valve is usually unavailable separately).
  • 4
    Turn the ignition switch to ON. Measure the voltage between the connector power supply terminal and ground (should be 12V±0.5V), and check the ground wire continuity (resistance < 1Ω). Use an oscilloscope to measure the control signal wire, perform the air conditioning system active test (Air Quality Sensor Test), and observe a 12V square wave or PWM signal.
  • 5
    If the circuit is normal but the fault persists, perform a mechanical inspection: remove the PM2.5 sensor assembly, blow compressed air (< 0.5MPa) into the air inlet, and simultaneously use the diagnostic tool to trigger the solenoid valve. Listen for a clear switching "click". If there is no actuation or the sound is faint, confirm the valve core is stuck and replace the assembly.
  • 6
    After installing the new part, use the diagnostic tool to perform 'A/C System Self-learning' or 'Air Quality Sensor Calibration' (required on some models). Clear the fault code, run the A/C system for 10 minutes, and confirm the fault code does not return and the system automatically switches between recirculation and fresh air modes based on PM2.5 concentration.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX DM solenoid valve coil open circuit caused air conditioning auto mode failure

✓
When the vehicle arrived at the workshop, the dashboard displayed 'Air Quality System Fault'. The air conditioning had been stuck in recirculation mode for a long time and could not switch automatically. I measured the resistance between pins 3-4 of the PM2.5 module solenoid valve with a multimeter; the reading showed infinite resistance (normal: 45Ω). Disassembly revealed oxidised dry solder joints inside the coil. I replaced the PM2.5 sensor assembly (part number: HA-8121400). The fault was resolved, and Auto mode returned to normal, allowing automatic switching to fresh air mode for purification.
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX petrol: valve spool sticking causes intermittent DTCs

✓
The owner reported intermittent air conditioning odor and a dashboard warning. The scan tool showed B110F as an intermittent fault. During disassembly, I found significant dust and cotton lint accumulated on the solenoid valve spool guide rail (the owner frequently drives through textile industrial areas), causing excessive resistance in armature movement. The controller detected an abnormal drive current waveform with peak current continuously exceeding 800mA. After cleaning the valve spool with electronic cleaner and applying silicone-based grease, the current waveform returned to normal and the fault code cleared. I advised the owner to replace the cabin air filter regularly (CN95 grade).
BYD DTC AI AnalysisFrom Chinese market (translated)

Dashboard wiring harness chafing caused intermittent power to the solenoid.

✓
After driving over rough roads, the warning light came on. Checked the PM2.5 module solenoid valve supply voltage, which was only 3.2V and unstable. Traced the wiring harness along the dashboard frame and found the body harness rubbing against a metal bracket. The insulation had worn through, causing partial fracture of the copper strands and a poor connection with about 15Ω resistance. Repaired the harness by soldering and sealing with heat shrink tubing, then rerouted and secured it, adding corrugated tubing and extra cable tie mounting points. This completely resolved the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Air conditioning controller driver chip failure caused multiple system faults

✓
Both B110F (PM2.5 solenoid valve) and B2A2F (recirculation motor) DTCs were present. The solenoid valve resistance and voltage measured normal individually, but the active test produced no current output. Removing and disassembling the climate control module revealed the solenoid valve driver chip (L99MC6 or similar H-bridge type) had overheated and burned, with scorch marks on the surface. Replaced the climate control module assembly (online immobiliser matching and configuration coding required). This resolved the fault. Root cause: a previously installed non-genuine dashcam; when splicing into the power supply, the installer accidentally touched the climate control wiring, causing a voltage surge.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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. Sources: [1]