AU
B110A02

DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2 — Qin Plus

Thermal Management System

DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle).

The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus.

The fault is essentially a communication link layer timeout.

Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage.

Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function.

In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.

8
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Internal fault in the PM2.5 sensor laser scattering module or damaged PCB CAN transceiver chip, preventing response to bus requests.
  • 2Loose sensor wiring harness connector (usually located inside the passenger-side dashboard), backed-out pins, or oxidized terminals causing increased CAN-H and CAN-L contact resistance (>5Ω) or an intermittent open circuit.
  • 3Sensor power supply fault: Blown B+ power supply fuse (constant or IGN power), excessive circuit voltage drop, or corrosion at ground points G301/G302 causing reference voltage drift.
  • 4CAN bus physical layer fault: Wiring harness wear at the firewall or instrument panel frame causing a short to ground or short to power, or damaged twisted-pair shielding introducing electromagnetic interference.
  • 5Degraded CAN port drive capability of the A/C controller (integrated into the thermal management unit), terminating resistor (120Ω) mismatch, or outdated software version causing communication protocol incompatibility.
What To Do
  • 1
    Use the VDS2000 or Launch X-431 diagnostic tool to read complete fault codes and freeze-frame data. Record the ambient temperature, IGN voltage, and vehicle speed at the time of the fault. Distinguish between current (Present) and historical (History) faults. If multiple CAN communication fault codes exist, troubleshoot common network issues first.
  • 2
    Remove the front passenger glovebox or cabin air filter cover and locate the PM2.5 sensor (usually a small black square box with an air inlet). Visually inspect the 4-wire connector (BAT+, GND, CAN-H, CAN-L) for oxidation or backed-out pins. Measure the supply voltage at the connector terminals (should be 12V±0.5V; some models use 5V). Ground resistance should be <1Ω.
  • 3
    Use a multimeter to measure the CAN line voltage: CAN-H to ground should be 2.5-3.5 V (dominant level), CAN-L to ground should be 1.5-2.5 V (recessive level), and the normal differential voltage is approximately 2 V. Disconnect power and measure the terminating resistance. It should be approximately 60 Ω (two 120 Ω resistors in parallel). If the resistance is abnormal (0 Ω or infinite), inspect the wiring for short or open circuits.
  • 4
    If static measurement is normal, use an oscilloscope (time base: 0.5ms/div, voltage: 2V/div) to capture the CAN waveform. Check for bit errors, frame errors, or overload frames. Also perform a sensor substitution test: bridge a known-good sensor of the same model and observe if the fault code changes to a history code to isolate a fault in the sensor itself.
  • 5
    If a wiring fault is confirmed, repair the damaged wiring harness using twisted pair wire (twist pitch within 20 mm) and restore the shielding layer. Avoid routing the harness parallel to the high-voltage wiring harness (orange). After repair, clear the fault code and perform a 15-minute air conditioning system self-check cycle. Confirm the 'PM2.5 concentration value' (AQI value) in the data stream changes normally during the smoke test.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM: Dashboard abnormal noise with automatic air conditioning mode failure

✓
2018 Qin Pro DM, 62,000 km. Owner reported that with the auto A/C on, the recirculation mode does not switch automatically based on air quality, and there is a rattle from inside the passenger side dashboard. The diagnostic tool read intermittent fault B110A02. Disassembly found the PM2.5 sensor retaining clip broken; the sensor body shook when the blower ran, causing the 4-pin connector to work loose. Resecured the sensor body, cleaned oxidation from the connector terminals and applied conductive grease, clearing the fault. Long-term vibration caused the mechanical mounting failure, leading to poor CAN bus communication contact.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV300 thermal management fault light stays on constantly and PM2.5 data stream is fixed at 0

✓
2017 BYD Qin EV300. After power-up, the high coolant temperature warning light illuminated. Retrieved DTC B110A02 (current). Live data showed the PM2.5 concentration reading stuck at 0μg/m³ regardless of environment. Measured sensor connector: 12V supply voltage normal, CAN-H voltage 0V. Traced the wiring and found thermal insulation at the firewall had worn through the harness, causing the CAN-H wire to short to ground. Repaired the damaged wires, re-wrapped with corrugated tubing, and adjusted the routing. Fault cleared.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro EV air conditioning system communication fault after modification

✓
2019 Qin Pro EV. After the owner fitted aftermarket ambient lighting, the HVAC panel flickered intermittently. The scan tool retrieved DTC B110A02 and multiple body CAN communication fault codes. Inspection revealed the installer had tapped power by cutting into the air conditioning controller wiring harness, compromising CAN bus signal integrity. We removed the unauthorised wiring, repaired the factory harness insulation, and ran new shielded twisted pair cable on an independent circuit. The fault cleared. For any CAN bus modifications, use an isolation transformer or independent power supply. Never splice into communication lines for power.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM sensor internal fault caused communication timeout.

✓
2019 BYD Qin Pro DM. No accident history, but DTC B110A02 logged frequently and reappeared about 50 km after each clear. Measured circuit voltage and resistance were normal; CAN waveform showed no abnormalities. Performed a swap test: installing the PM2.5 sensor from the faulty car into a normal car transferred the fault; installing a normal car's sensor into the faulty car restored communication. Traced the fault to poor thermal stability of the internal CAN transceiver chip in the PM2.5 sensor. Replaced the sensor assembly (P/N: MEH-8123100) and permanently resolved the issue.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV300 software version incompatibility causing false positives

✓
2017 BYD Qin EV300. After a battery pack replacement, a B110A02 DTC appeared, but the PM2.5 function worked normally (data stream updating normally, automatic recirculation functioning). Inspection found that a repair shop had previously flashed non-official software onto the AC controller. A BYD authorised service centre reflashed the system with official V1.8 software and relaxed the CAN communication timeout threshold from 500ms to 800ms. The fault code did not return. This is a software calibration issue, not a hardware fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM: Dashboard abnormal noise with automatic air conditioning mode failure

✓
2018 BYD Qin Pro DM, 62,000 km. Owner reported that with automatic climate control on, the recirculation mode failed to switch automatically based on air quality, and a noise came from inside the passenger side dashboard. Diagnostic scanner retrieved fault code B110A02, indicating an intermittent fault. Inspection found the PM2.5 sensor retaining clip had fractured, allowing the sensor body to vibrate when the blower ran and causing the 4-pin connector to come loose. Re-secured the sensor body, cleaned oxidation from the connector terminals, and applied conductive grease. Fault resolved. Analysis: prolonged road vibration caused the mechanical mount to fail, leading to poor CAN communication contact.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro EV air conditioning system communication fault after modification

✓
2019 BYD Qin PRO EV. After the owner fitted aftermarket ambient lighting, the air conditioning panel flickered intermittently. The scan tool logged B110A02 and multiple body CAN communication faults. Inspection revealed the installer had spliced into the air conditioning controller wiring harness to draw power, compromising CAN bus signal integrity. Removed the unauthorised wiring, repaired the factory harness insulation, and rerouted the lighting using shielded twisted pair cable on a separate circuit, which resolved the fault. For any CAN bus modifications, use isolation transformers or independent power supplies. Never tap power from communication lines.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM sensor internal fault caused communication timeout.

✓
2019 Qin Pro DM, no accident history, frequently sets DTC B110A02. Code returns after clearing and driving about 50 km. Measured circuit voltage and resistance — normal. CAN waveform — no abnormality. Performed substitution test: installed the faulty car's sensor into a known-good car, and the fault followed; swapped the good sensor into the faulty car, and communication restored. Diagnosed poor thermal stability in the PM2.5 sensor's internal CAN transceiver chip. Replaced sensor assembly (part number: MEH-8123100). Fault resolved.
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.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]