AU
B110B

DTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2 — Seal 6 EV

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 — Seal 6 EV
  • 1Worn internal carbon brushes or a seized bearing in the air pump motor prevents rotation or causes excessive startup current, triggering overcurrent protection.
  • 2Poor connection, backed-out terminal, or oxidized pin at the PM2.5 sensor wiring harness connector, interrupting the power supply, ground, or PWM control signal.
  • 3Damage to the MOSFET or filter capacitor on the air pump drive circuit board inside the sensor assembly causes abnormal drive voltage.
  • 4Control signal wire from the air conditioning controller (ACU) to the PM2.5 sensor shorted to ground or power
  • 5After prolonged use, a clogged air pump inlet filter causes excessive load, or a damaged internal impeller causes mechanical seizure.
What To Do
  • 1
    Use VDS or a 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 freeze frame data.
  • 2
    Remove the PM2.5 sensor assembly located inside the passenger-side dashboard or near the A/C filter. Inspect the exterior for damage and 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. Normal resistance 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 PWM signal at approximately 1 kHz). If the signal is normal but the air pump does not operate, replace the sensor assembly. If there is no signal output, 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" (via diagnostic tool special functions). Clear the fault codes, start the vehicle, and check the air pump operating sound (a slight humming noise is normal). Verify the air quality value 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 Seal 6 EV 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.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.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.
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]