AU
B2A2992

This DTC indicates the HVAC Defrost Mode Actuator fails to reach the control module's commanded target position within the specified time — Qin Plus

Thermal Management System

This DTC indicates the HVAC Defrost Mode Actuator fails to reach the control module's commanded target position within the specified time.

The defrost motor, typically a stepper motor or DC gear motor with position feedback (potentiometer or Hall sensor), drives the mode door to engage the front windshield defrost mode.

After sending a position command, the HVAC control module continuously monitors the position sensor feedback voltage (typically a 0-5V analog signal or PWM signal).

The module triggers DTC B2A2992 if the deviation between the actual and target positions exceeds the threshold (e.g., 5%-10%) within the specified time (typically 10 seconds), or if it detects abnormal motor current (stall current).

This fault disables the defrost function or causes abnormal airflow distribution.

In low-temperature and high-humidity environments, the system fails to defog the front windshield, severely compromising driving safety.

The B2A2992 fault code on the Qin Plus indicates the HVAC defrost mode actuator is not reaching the position commanded by the control module in time. Severity is medium, as poor defrosting can reduce windshield visibility. Common causes include jammed or broken actuator gears, a weak motor, or a stuck air flap/linkage. The recommended fix is to visit an authorised dealer for diagnosis and actuator or flap repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Jammed internal gears, broken plastic gear teeth, or worn motor carbon brushes in the defrost flap actuator cause insufficient driving force.
  • 2Deformed air flap shaft inside the HVAC housing, broken or detached plastic linkage, or foreign matter (such as leaves, foam particles, or paper labels) jamming the air flap.
  • 3Poor contact or wear in the position sensor (potentiometer) causing an erratic signal, or an open or short circuit in the sensor power supply or signal wiring.
  • 4Poor contact, terminal back-out, or oxidized/corroded pins at the actuator wiring harness connector; or an unsecured wiring harness after dashboard removal and installation causing wear and an open circuit.
  • 5HVAC control module internal drive circuit fault, software logic error, or loss of air flap position learning data (common after power disconnection or module replacement without initialization)
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (ED400/VDS) to read the data stream. Compare the 'Defrost Air Door Target Position' and 'Actual Position' values to confirm the deviation. Simultaneously check the data of other air doors (mode motor, fresh/recirculated air motor) to rule out a bus fault.
  • 2
    Operate the A/C panel to cycle through the defrost/face/foot modes. Listen for a 'click' or continuous 'buzzing' noise inside the dashboard to determine if the motor is attempting to operate but is jammed.
  • 3
    Remove the front passenger glove box or lower dashboard trim panel. Visually inspect the defrost actuator (typically located on the right or top of the HVAC housing) installation condition and linkage connection, and check the air flap shaft for breakage.
  • 4
    Disconnect the actuator connector and measure the motor winding resistance (normal value approximately 20–100 Ω, depending on the specific model) and the position sensor resistance (must change smoothly as the gear rotates, without jumps or open circuits). Inspect the connector pins for oxidation or push-out.
  • 5
    If mechanical components and wiring are normal, use the diagnostic tool to perform the 'Air Flap Position Learning' or 'A/C Initialization' procedure (for some models, select 'Special Functions' - 'Air Flap Calibration' via VDS). If learning fails or the fault recurs, replace the defrost air flap actuator assembly and perform position learning again.
Real-World Cases
BYD DTC AI Analysis

Song MAX broken defrost damper linkage causes sticking

✓
Symptoms: 2018 Song MAX — no airflow from vents when front defrost mode selected; clicking noise from inside the dashboard; DTC B2A2992 stored. Diagnosis: Removed the glove box to inspect the defrost actuator. Gears operated normally, but the white plastic linkage connecting to the flap had snapped, trapping the flap in the face-level vent position. Repair: Replaced the HVAC box flap linkage assembly (some models require the complete flap assembly), reconnected the actuator, and performed the flap position learning procedure. Fault cleared.
BYD DTC AI Analysis

Qin EV: Defrost actuator motor internal open circuit

✓
Symptom: 2019 Qin EV defrost function failed suddenly. No warning lamp, but historic DTC B2A2992 stored. Diagnosis: Supply voltage at the actuator connector measured 12V (normal). Motor winding resistance measured infinite (open circuit), confirming internal coil break. Disassembled the actuator; motor brushes were worn out. Repair: Replaced the defrost air door actuator (part number likely EQEA-8101810 or similar). After installation, ran 'HVAC flap initialization' using VDS; live data confirmed normal position tracking.
BYD DTC AI Analysis

Song MAX – Loose wiring connector causing intermittent fault

✓
Symptoms: 2017 Song MAX instrument cluster occasionally displayed air conditioning fault warning when driving on rough roads. Diagnostic tool retrieved intermittent fault code B2A2992. Diagnosis: Found broken locking tab on actuator connector and enlarged, loose pins. Position signal in data stream jumped when gently shaking wiring harness. Resolution: Repaired wiring harness connector (replaced connector or tightened pins), secured harness with cable ties to prevent rubbing against dashboard frame, cleared fault codes. No recurrence after one week of monitoring.
BYD DTC AI Analysis

BYD Qin EV300: AC not initialized after battery pack replacement

✓
Symptoms: 2017 BYD Qin EV300 set false DTCs B2A2992 and B2A2914 (defrost motor short to ground/open circuit) and the defrost mode wouldn't hold after the high-voltage battery pack was replaced and the 12V auxiliary battery disconnected. Diagnosis: Line checks found no shorts, the actuator tested normal, but the data stream showed position feedback voltage locked at 0V. Fix: Using the scan tool, navigate to Air Conditioning System > Special Functions > Air Door Position Learning and complete the limit position calibration for all air doors (defrost, mode, recirculation) as prompted. The DTCs cleared automatically and system operation returned to normal.
BYD DTC AI Analysis

Song MAX: Foreign object jamming air flap in HVAC unit

✓
Symptoms: The owner of a 2019 Song MAX reported weak airflow in defrost mode accompanied by a squeaking friction noise. DTC B2A2992 stored. Diagnosis: Removed the blower motor and found leaves lodged in the air outlet. Further disassembly of the HVAC box revealed a paper label jammed at the edge of the defrost damper, preventing full closure. Continuous actuator stall triggered the fault. Resolution: Cleared all foreign objects from the HVAC box. Checked the damper sealing sponge for detachment (replace if necessary). Reset the actuator and tested all modes for smooth switching.
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.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.B110BDTC 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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus overview →
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.