AU
B2A4B14

This DTC indicates a fault in the drive circuit of the HVAC Recirculation Air Door Actuator motor — Qin Plus

Thermal Management System

This DTC indicates a fault in the drive circuit of the HVAC Recirculation Air Door Actuator motor.

Specifically, a "short to ground" indicates insulation failure between the motor supply line (typically the PWM control line or power line) and the vehicle body ground (GND), causing abnormal current leakage.

An "open circuit" indicates a broken internal motor coil, a loose connector, or a severed wiring harness.

This motor switches the HVAC air door between fresh air and recirculation modes.

A fault prevents mode switching or causes the door to stick in a fixed position, reducing cabin temperature control efficiency.

In extreme cases, this reduces battery thermal management performance (e.g., preventing effective heat dissipation via fresh air mode).

Therefore, the system classifies this as a severe fault.

The B2A4B14 fault code on the Qin Plus indicates a high-severity fault in the HVAC recirculation air door actuator motor circuit, such as a short to ground or open circuit. This can stop the system switching between fresh air and recirculation modes. Common causes include a burnt or shorted actuator motor coil, or corroded, loose, or damaged wiring/connectors. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Recirculation air flap actuator motor internal coil burnt out or short-circuited: Prolonged motor jamming or overload damages the coil insulation, resulting in a short to ground or internal open circuit.
  • 2Wiring harness and connector fault: Water ingress or poor sealing causes pin corrosion or oxidation at the wiring harness connector near the HVAC unit (usually behind the glovebox or firewall), or vehicle vibration loosens the male and female terminals.
  • 3Mechanical jamming causes motor damage: Foreign matter (such as leaves or accumulated dust) jams the air flap mechanism, or the linkage deforms. This causes excessive motor stall current, eventually burning out the drive circuit or motor winding.
  • 4Air conditioning controller (HVAC ECU) internal fault: Damage to the internal H-bridge drive circuit or MOSFET causes an abnormal output signal (such as a short to ground), triggering a false fault.
  • 5Wiring harness worn or damaged: An improperly secured wiring harness in the engine compartment or instrument panel rubs against metal body edges, damaging the insulation and causing a short to ground.
What To Do
  • 1
    Diagnostic confirmation: Use the BYD VDS diagnostic tool to read all DTCs. Confirm only B2A4B14 or related fault codes are present. Record freeze frame data (such as motor duty cycle and position feedback value at the time of the fault). Clear the fault codes, operate the fresh air/recirculation switch, and verify if the fault reoccurs.
  • 2
    Visual and connector inspection: Remove the glove box or front passenger lower trim panel and locate the recirculation flap actuator (usually marked 'REC' or 'Intake'). Check the connector for looseness, backed-out pins, or green/white corrosion. Measure the connector terminal resistance to ground to check for a short circuit.
  • 3
    Actuator unit inspection: Disconnect the connector and use a multimeter to measure the resistance between the two motor terminals (normal range is typically 30-80Ω; refer to the vehicle repair manual for specific values). A resistance of 0Ω indicates a short circuit; infinite resistance indicates an open circuit. Also, manually move the air flap blade to confirm the mechanical mechanism operates without binding or abnormal noise.
  • 4
    Harness continuity and insulation test: Measure harness continuity (power wire, ground wire, signal wire) from the actuator connector along the harness toward the air conditioning controller. Use a megohmmeter or a multimeter on the high-resistance setting to measure the insulation resistance of each wire to ground. Resistance must be greater than 1MΩ. Inspect harness bend points passing through the firewall and hinges.
  • 5
    Controller output check: Connect the diagnostic tool and perform the Actuation Test. Observe the PWM output waveform and voltage from the air conditioning controller to the recirculation motor. If the controller output is normal but the motor does not operate, replace the actuator. If the controller has no output or the output is shorted to ground, repair or replace the air conditioning controller.
  • 6
    Component replacement and repair: Replace the recirculation air flap actuator motor (Note: some models require replacing the complete air flap housing assembly) or repair the damaged wiring harness (seal with heat-shrink tubing and restore original wrapping). If the flap mechanism binds, clear foreign matter and apply specified grease.
  • 7
    Calibration and Verification: After completing the repair, use VDS to execute the 'Door Motor Calibration' procedure to teach the controller the flap limit positions. Operate the recirculation/fresh air switch and confirm the flap moves smoothly without abnormal noise. Read the data stream to confirm the position feedback value changes according to the command (recirculation is typically 0-20%, fresh air is 80-100%). Perform a road test to verify the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

Song MAX recirculation door jammed, motor burned out

✓
A 2018 BYD Song MAX DM with 60,000 km displayed "Air Conditioning System Fault" on the dashboard. Found DTC B2A4B14. Disassembly revealed mud ingress at the recirculation door actuator connector and the door shaft jammed with accumulated leaves and dust. The motor continuously attempted to drive while stalled, overheating and burning out the internal coil. Measured resistance: 0.5Ω (short to ground). Solution: Cleaned the door mechanism and foreign objects from the HVAC unit, lubricated the shaft, replaced the recirculation door actuator, and cleaned and waterproofed the wiring harness connector. Fault resolved.
BYD DTC AI Analysis

Qin Pro EV HVAC unit wiring harness chafed, shorted to ground

✓
2019 BYD Qin Pro EV. Intermittent B2A4B14 DTC. When the fault occurred, the recirculation mode would not switch. Inspection revealed the fault occurred on rough roads. Removed the passenger side dashboard and found the recirculation flap actuator power supply wire (pink) had chafed against a metal body bracket where it passes through the firewall. Damaged insulation caused an intermittent short to earth. Measured resistance from the wire to earth with a multimeter; resistance fluctuated between 0–10 ohms when moving the harness. Repair: Cut out the damaged section, soldered in an extension, and insulated with double-layer heat shrink tubing. Re-secured the harness routing and added a rubber grommet to prevent chafing. Fault has not reoccurred.
BYD DTC AI Analysis

Qin EV300 Actuator Internal Open Circuit Fault

✓
2017 BYD Qin EV300. Air conditioning recirculation mode inoperative, system forced to fresh air mode with DTC B2A4B14 stored. Scan tool live data showed 'Invalid' for flap position. Measured motor coil resistance at the recirculation flap actuator connector: open circuit (infinite resistance). Disassembled the actuator: gearset intact, but motor brushes severely worn causing open circuit. This model uses a sealed, non-serviceable actuator. Replaced the air conditioning recirculation flap actuator assembly (part number similar to BG-8112600). Performed flap calibration after replacement. Recirculation and fresh air functions returned to normal.
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.