AU
B110B

DTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2 — Atto 3

Thermal Management System

DTC 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.

7
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Worn internal carbon brushes or a seized bearing in the air pump motor prevents rotation or draws excessive start-up current, triggering overcurrent protection.
  • 2Poor contact, backed-out terminals, or oxidized pins in the PM2.5 sensor wiring harness connector, interrupting the power supply, ground, or PWM control signal.
  • 3A damaged MOSFET or filter capacitor on the air pump drive circuit board inside the sensor assembly causes abnormal drive voltage.
  • 4Air conditioning controller (ACU) output control signal wire to the PM2.5 sensor shorted to ground or power.
  • 5After prolonged use, a blocked air pump inlet filter causes excessive load, or a damaged internal impeller causes mechanical seizure.
What To Do
  • 1
    Use a VDS or Launch diagnostic tool to read the complete fault codes. Confirm if it is a current fault (Current DTC), check for sub-codes such as B110B07 (air pump mechanical fault), and record the freeze frame data.
  • 2
    Remove the PM2.5 sensor assembly located inside the passenger-side dashboard or near the cabin air filter. Inspect the exterior for damage. Check the connector for looseness, water ingress, or corrosion. Measure the voltage and waveform at plug terminal 1 (constant power B+), terminal 2 (ground GND), and terminal 3 (LIN line or PWM control) to verify normal readings.
  • 3
    Disconnect the sensor connector and directly measure the resistance across the air pump motor terminals. The normal value is 15-30 Ω. If the resistance is infinite (open circuit) or close to 0 Ω (short circuit), replace the PM2.5 sensor assembly.
  • 4
    If motor resistance is normal, use an oscilloscope to check the air pump drive signal from the air conditioning controller (typically a 1kHz PWM signal). If the signal is normal but the air pump does not operate, replace the sensor assembly. If no signal is present, check wiring harness continuity and replace the air conditioning controller if necessary.
  • 5
    After replacing the sensor, perform "PM2.5 Sensor Calibration" or "Air Quality System Reset" using the diagnostic tool special functions. Clear the fault code. Start the vehicle and check the air pump operating sound (a slight humming noise is normal). Confirm the air quality reading displays normally on the instrument cluster.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX abnormal air pump noise followed by air quality detection failure

✓
2018 BYD Song MAX, 62,000 km. The owner reported the automatic climate control could not switch between recirculation and fresh air, and the dashboard PM2.5 reading consistently showed '--'. Retrieved DTC B110B (current fault). Removed the PM2.5 sensor behind the glovebox and found obvious signs of sticking in the air pump. When powered, the pump emitted a harsh grinding noise then stopped. The air pump coil resistance measured open circuit. Replaced the OEM PM2.5 sensor assembly (Part No.: HA-8113100). After sensor calibration, the air quality display returned to normal and the automatic recirculation function recovered.
BYD DTC AI AnalysisFrom Chinese market (translated)

Open circuit in PM2.5 air pump wiring after dashboard repair

✓
After an evaporator core replacement at a 4S shop, the HVAC warning light came on in a 2019 Song MAX. A diagnostic tool read DTC B110B with intermittent status. Inspection found that during dashboard removal, the PM2.5 sensor harness (on the right side of the HVAC unit) had been pinched. The pink control wire (LIN line) had fractured copper strands inside while the outer insulation remained intact, causing intermittent poor contact. The shop repaired the broken wire, re-wrapped the harness, and secured it with enough clearance from the dashboard frame. The fault was resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Water entering the sensor connector caused a short circuit in the air pump drive.

✓
Water pooled under the passenger-side A-pillar of a 2017 Song MAX after the front windscreen rubber seal deteriorated and leaked. The PM2.5 sensor connector, located above the pooled water, had water ingress and corrosion. Green copper oxide formed between the pins, shorting the air pump power supply terminal to ground. The sensor-side connector resistance measured 2Ω (abnormal short). Replaced the sensor assembly and serviced the connector (cleaned with electronic cleaner, applied conductive grease). After repairing the windscreen seal, the fault codes cleared and the system worked normally.
BYD DTC AI AnalysisFrom Chinese market (translated)

AC controller software falsely reporting air pump fault

✓
2018 Song MAX intermittently set DTC B110B. Inspected the air pump and wiring; both normal. The fault mostly occurred after prolonged sun exposure. Checked the technical service bulletin and confirmed early AC controller software (below V1.2) caused current sampling deviations for the air pump in high temperatures, resulting in false DTCs. Upgraded the AC controller software to V1.5 using VDS2000. Monitored the air pump operating current after the upgrade (normal range 80–120mA); the DTC no longer appeared.
BYD DTC AI AnalysisFrom Chinese market (translated)

Open circuit in PM2.5 air pump wiring after dashboard repair

✓
After a 4S shop replaced the evaporator core on a 2019 Song MAX, the HVAC warning light came on. The scan tool pulled DTC B110B with intermittent status. Inspection found that when the dashboard was removed, the PM2.5 sensor harness (located on the right side of the HVAC unit) was pinched, which broke the copper strands inside the pink control wire (LIN line) while the outer insulation stayed intact, causing intermittent poor contact. We repaired the harness, re-wrapped and secured it, and ensured sufficient clearance between the harness and the dashboard frame. The fault was fixed.
BYD DTC AI AnalysisFrom Chinese market (translated)

Water entering the sensor connector caused a short circuit in the air pump drive.

✓
A 2017 Song MAX had water pooling below the passenger-side A-pillar from a deteriorated front windscreen rubber seal. The PM2.5 sensor connector—located above the water—suffered water ingress and corrosion. Green copper corrosion formed between the connector pins, causing a short circuit between the air pump power supply terminal and earth terminal. Measured resistance at the sensor side connector was 2 Ω (abnormal short circuit). Replaced the sensor assembly and serviced the connector (cleaned with electronic cleaner, applied conductive grease). After repairing the windscreen seal, fault codes cleared and the system worked normally.
BYD DTC AI AnalysisFrom Chinese market (translated)

AC controller software falsely reporting air pump fault

✓
2018 Song MAX intermittently set DTC B110B. Inspected the air pump and wiring — both normal. The fault mostly occurred after prolonged sun exposure. Checked the technical service bulletin and confirmed that early AC controller software (below V1.2) had current sampling deviations for the air pump in high temperatures, causing false positives. Upgraded the AC controller software to V1.5 using VDS2000. Monitored air pump operating current after the upgrade (normal range 80-120mA); the fault no longer appeared.
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]