AU
B110B07

This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2 — Seal U

Thermal Management System

This 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.

7
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Air pump motor mechanically seized or carbon brushes worn: After long-term use, the air pump bearing lacks lubrication, the impeller seizes, or worn motor carbon brushes prevent the motor from starting.
  • 2Power supply circuit fault: Blown PM2.5 sensor power supply fuse, poor connector contact, or oxidized or backed-out pins causing insufficient power supply voltage to the air pump.
  • 3Internal sensor circuit damage: air pump driver chip burnt out due to overheating, PCB moisture corrosion, or abnormal interlock control logic between the laser and air pump.
  • 4Air intake system blockage: Dust, lint, or foreign matter blocks the PM2.5 sensor air inlet, causing excessive air pump load and triggering overcurrent protection.
  • 5Wiring harness wear and short circuit: High engine compartment temperatures degrade and damage the air pump drive wiring harness insulation, causing a short to body ground.
What To Do
  • 1
    Use the VDS2000/6000 diagnostic tool to read the complete fault codes, confirm whether B110B07 is a current or history fault, and record freeze frame data (ambient temperature, vehicle speed, etc.).
  • 2
    Visually inspect the PM2.5 sensor installation. Confirm the mounting bracket is secure and the sensor air inlet filter has no visible blockages.
  • 3
    Disconnect the sensor connector and measure the voltage between PIN1 (constant power +B) and PIN2 (ground); the voltage should be 12V±0.5V. Measure the resistance and waveform between PIN3 (LIN line or PWM signal line) and ground to confirm normal communication.
  • 4
    Remove the sensor assembly and measure the resistance across the air pump motor terminals. Normal resistance is 50-200 Ω. Infinite resistance indicates an open circuit in the air pump. Resistance below 20 Ω indicates an internal short circuit.
  • 5
    Connect an external 12V regulated power supply directly to the air pump. Observe whether it operates normally without abnormal noise to verify the mechanical condition of the air pump.
  • 6
    If the air pump is damaged, replace the PM2.5 sensor assembly (part number usually starts with 5A- or EP-, depending on model year). Verify the new part includes a sealing ring.
  • 7
    After reassembly, clear the fault code, start the vehicle, and set the air conditioning to recirculation mode. Observe the diagnostic tool data stream to verify the PM2.5 value changes normally (hold a cigarette near the air intake to test responsiveness).
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM: Intermittent PM2.5 sensor fault after driving through water

✓
After wading, the instrument cluster intermittently displayed an air quality sensor fault. Inspection found the PM2.5 sensor mounted above the air conditioning box; the water level had exceeded the sensor base, causing water ingress and rust in the internal air pump motor. Disassembly revealed the air pump impeller shaft rusted and seized, and resistance measured open circuit. Replaced the sensor assembly, applied waterproof silicone grease to the connector, and rerouted the wiring harness to prevent water pooling at low points. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV300 A/C auto mode inoperative with DTC B110B07

✓
Owner reported the auto climate control would not switch between recirculation and fresh air automatically. Read current fault code B110B07. Removed and inspected the PM2.5 sensor and found its intake completely blocked by willow catkins. The air pump overload caused the driver chip to go into thermal protection. After cleaning the debris from the filter screen, the air pump still would not start. Resistance check confirmed the pump coil was burnt out (abnormal resistance). Replaced the sensor and installed a pre-filter. Instructed the owner to regularly clean debris from the climate control intake. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Chafed wiring loom caused intermittent short in air pump power feed.

✓
The warning light occasionally illuminated when driving on rough roads. Power supply to the PM2.5 sensor connector was normal, but the fault returned when shaking the wiring harness. Tracing the harness revealed the air pump power wire insulation had been cut by a metal edge at the firewall grommet, occasionally shorting to ground and blowing the fuse. Repaired the damaged wiring, wrapped it with corrugated tubing, repositioned the retaining clips, and replaced the blown F2/11 fuse (10A). The fault did not return.
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor aging caused degraded accuracy, triggering false fault codes

✓
5-year-old BYD Qin EV logged a DTC for air pump failure. Measured air pump resistance and supply voltage — both normal. Further scope check of the air pump drive PWM signal showed the ECU commanding 100% duty cycle, while the pump speed feedback signal remained below the threshold. Determined the air pump had mechanically worn and was spinning too slowly. After replacing the air pump, compared old and new pump flow rates under identical conditions; the old pump flowed 60% less. Confirmed air pump wear. The fault code cleared after replacement.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV300 A/C auto mode inoperative with DTC B110B07

✓
The owner reported the automatic climate control would not switch between fresh air and recirculation modes automatically. Retrieved DTC B110B07 (active). Removed and inspected the PM2.5 sensor and found willow catkins completely blocking the intake, causing the air pump driver chip to overheat under excessive load. After clearing debris from the filter screen, the pump still did not start. Measured the pump coil and found it burnt out (abnormal resistance). Replaced the sensor, fitted a pre-filter screen, and advised the owner to regularly clear debris from the A/C air intake. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Chafed wiring loom caused intermittent short in air pump power feed.

✓
The warning light occasionally illuminated when driving on rough roads. Checked the PM2.5 sensor connector and found normal power supply, but shaking the wiring harness caused the fault to return. Traced the harness and found the metal edge at the firewall grommet had cut the air pump power wire insulation, occasionally shorting to body earth and blowing the fuse. Repaired the damaged wiring, wrapped it with corrugated tubing, repositioned the retaining clips, and replaced the blown F2/11 fuse (10A). The fault has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

Sensor aging caused degraded accuracy, triggering false fault codes

✓
5-year-old BYD Qin EV logged a DTC for air pump failure. Measured air pump resistance and supply voltage—both normal. Further checked the air pump drive PWM signal with an oscilloscope and found the ECU commanding 100% duty cycle, but the air pump speed feedback signal remained below the threshold. Determined the air pump had mechanically aged and was spinning too slowly. After replacing the air pump, compared flow rates of the old and new pumps under identical conditions; the old pump showed a 60% flow drop, confirming wear. The fault code cleared after replacement.
Other Seal U 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]