AU
B2A2B92

This fault code indicates the driver-side HVAC (Heating, Ventilation, and Air Conditioning) temperature blend door actuator (hot/cold blend door motor) cannot reach the target position or the position feedback signal is abnormal — Atto 8

Thermal Management System

This fault code indicates the driver-side HVAC (Heating, Ventilation, and Air Conditioning) temperature blend door actuator (hot/cold blend door motor) cannot reach the target position or the position feedback signal is abnormal.

The actuator uses a stepper motor or DC motor to drive a gear mechanism, adjusting the hot/cold blend door opening (0-100%).

This accurately controls the airflow mixing ratio through the heater core and evaporator, providing stepless adjustment of the outlet air temperature.

The air conditioning controller (AC ECU) logs this fault code if the deviation between the actual and target positions continuously exceeds the calibrated threshold (typically 5-10%) or if the motor stall current times out.

Triggering conditions include a faulty motor drive circuit, position sensor (potentiometer) signal drift, a binding gear drive mechanism, or excessive mechanical resistance at the blend door shaft.

This fault causes driver-side temperature adjustment failure, abnormal outlet air temperature (stuck excessively cold or hot), unstable temperature control in automatic air conditioning mode, or a clicking gear noise during temperature adjustment.

3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Worn, broken, or missing teeth in the internal plastic gear set of the air mix door actuator cause drive slippage or binding, preventing the door from reaching the target position.
  • 2Poor contact, carbon track wear, or resistance drift in the actuator position sensor (potentiometer) causes an inaccurate or erratic position feedback signal.
  • 3Mechanical binding of the air flap linkage or shaft (e.g., foreign objects in the HVAC housing, worn or deformed air flap shaft bushing, or lack of lubrication), causing excessive motor load and preventing the motor from reaching the target position.
  • 4Excessive contact resistance in the actuator power supply circuit (oxidized or loose connector pins) or poor grounding causes insufficient drive voltage and reduces motor torque.
  • 5Internal drive circuit fault or lost software calibration data in the air conditioning controller (AC ECU), causing it to output incorrect control signals or fail to recognize position feedback.
What To Do
  • 1
    Read fault codes using BYD VDS or a dedicated diagnostic tool. Confirm B2A2B92 is active and cannot be cleared. Check for accompanying fault codes (e.g., B2A2B14 circuit fault, B2A2C12 front passenger side fault). Record the ambient temperature and air flap position data stream at the time the fault occurred.
  • 2
    Perform the air flap actuator self-learning/initialization procedure: Access the air conditioning system special functions using the diagnostic tool, select 'Air Flap Initialization' or 'Actuator Reset', or disconnect the battery negative terminal for 10 minutes and reconnect power. Observe if the fault code changes to a history code or disappears.
  • 3
    Inspect the driver-side air mix door actuator wiring harness connector (located below the center of the instrument panel, on the driver-side evaporator housing). Check the pins for backing out, oxidation, or corrosion. Measure the supply voltage (should be 12V ± 0.5V) and ground resistance (<1Ω). Check the LIN line or PWM signal line waveform (depending on the specific vehicle topology).
  • 4
    Remove the air flap actuator (dashboard removal is usually unnecessary; access it from the driver's footwell). Manually turn the air flap shaft to check for mechanical resistance. Inspect the air flap linkage for detachment or deformation. Check the HVAC housing interior for foreign objects (such as leaves or pens) obstructing air flap movement. Clean and apply silicone-based grease if necessary.
  • 5
    Test the actuator: Connect the diagnostic tool, perform an active test, and observe if the motor runs smoothly; measure the position sensor resistance (value must change smoothly as the motor turns, without jumps or open circuits; typical range is 0-5 kΩ or 0-10 kΩ); measure the motor winding resistance (typically 30-100 Ω; refer to the workshop manual for specific values).
  • 6
    If the actuator internal gears are damaged or the sensor fails, replace the driver side air mix door actuator (verify the part number matches the vehicle model, as actuators differ between models such as Song MAX and Qin Pro). Position the air door in the middle before installation. After installing the actuator, perform the air door position self-learning procedure.
  • 7
    Clear the fault code and perform a function check: Adjust the temperature through the full range from LO to HI in both automatic and manual modes. Listen for smooth motor operation with no abnormal noise. Observe the data stream to verify the deviation between the actual position and target position is <3%. Confirm the driver-side air outlet temperature changes normally with the adjustment.
Real-World Cases
BYD DTC AI Analysis

Yuan PLUS dashboard rattle with DTC B2A2B92

✓
The owner scanned with a Launch golo pro4 and found DTC B2A2B92 (driver-side temperature control motor not reaching position) and B2A2B14 (driver-side temperature control motor short-to-ground or open circuit) in the body module–AC controller. The symptom was a faint, intermittent clicking noise from inside the dashboard, most noticeable when adjusting the temperature or starting the AC. Although the motor wasn't reaching position, cooling and heating still worked. Upon disassembly, the owner found slight wear on the actuator gear. Since the function hadn't completely failed and the part needed ordering, the owner decided to defer the repair and replace the actuator assembly when the fault worsened.
Original source ↗
BYD DTC AI Analysis

Qin EV Intermittent AC Cooling Failure Associated with DTC B2A2B92

✓
The owner reported the vehicle A/C frequently stopped cooling but returned to normal after driving for a period or restarting the vehicle. Scanning showed fault code B2A2B92 (HVAC blend door actuator position fault). Further inspection found the driver's side temperature blend door stuck at maximum heat (100%) when the fault occurred. Even with the temperature set to low, the mixed hot and cold air could not achieve cooling. This case shows B2A2B92 causes not only abnormal noise but can also stick the blend door in a fixed position, causing intermittent A/C failure. Inspect the blend door actuator mechanical linkage and internal gear condition.
Original source ↗
BYD DTC AI Analysis

Song MAX Blend Door Actuator Gear Wear Replacement Case

✓
A 2018 Song MAX owner reported the driver's side AC temperature would not adjust and remained stuck on warm. The technician scanned with VDS and found DTC B2A2B92. Data stream showed target position at 20% with actual position stuck at 95% (full heat). After removing the driver's side temperature blend door actuator, the technician found severe wear and broken teeth on both the drive and driven gears in the internal plastic gear set; the motor spun freely without moving the door. The technician replaced the blend door actuator (part number: HAD-8113210), ran the door initialization procedure, cleared the fault code, and restored normal temperature control. This case represents a typical mechanical failure mode for DTC B2A2B92.
Other Atto 8 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.