AU
B2A4B14

This DTC indicates a fault in the drive circuit of the HVAC Recirculation Air Door Actuator motor — Seal 6 EV

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 Seal 6 EV 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 and recirculated air. Common causes include a failed actuator motor coil or corroded, loose wiring connectors. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Recirculation air flap actuator motor internal coil burnt out or short-circuited: Prolonged motor jamming or overloading damages the coil insulation, causing 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 glove box or at the firewall), or vehicle vibration loosens the male and female terminals.
  • 3Mechanical jamming causing motor damage: Foreign matter (such as leaves or accumulated dust) jams the air flap mechanism, or the linkage mechanism deforms, generating excessive motor stall current and ultimately burning out the drive circuit or motor windings.
  • 4Air conditioning controller (HVAC ECU) internal fault: Damage to the controller's internal H-bridge drive circuit or MOSFET causes an abnormal output signal (such as a short to ground), triggering a false fault.
  • 5Harness wear or damage: Improperly secured wiring harnesses in the engine compartment or instrument panel rub 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 if only B2A4B14 is present or if related fault codes accompany it. Record freeze frame data (such as the motor duty cycle and position feedback values when the fault occurred). Clear the fault codes, operate the fresh air/recirculation switch, and verify if the fault returns.
  • 2
    Visual and connector inspection: Remove the glove box or front passenger lower trim panel and locate the recirculation air flap actuator (usually marked 'REC' or 'Intake'). Check for a loose connector, backed-out pins, and green or white corrosion. Measure the connector terminal-to-ground resistance 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 exact specifications). A resistance of 0Ω indicates a short circuit; infinite resistance indicates an open circuit. 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 toward the air conditioning controller. Use a megohmmeter or the high-resistance range of a multimeter to measure the insulation resistance of each wire to ground. Resistance must be greater than 1 MΩ. Inspect harness bend points passing through the firewall and hinges.
  • 5
    Controller output check: Connect the diagnostic tool and perform an Actuation Test. Observe the air conditioning controller PWM output waveform and voltage 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 (on some models, replace the complete flap housing assembly), or repair the damaged wiring harness (seal with heat-shrink tubing and restore the original wrapping). If the flap mechanism binds, remove foreign matter and apply the specified grease.
  • 7
    Calibration and verification: After completing the repair, use VDS to perform the 'Door Motor Calibration' procedure to allow the controller to learn the air flap limit positions. Operate the recirculation/fresh air switch and confirm the air flap moves smoothly without abnormal noise. Read the data stream to confirm the position feedback value changes according to the command (recirculation is usually 0-20%, fresh air is 80-100%). Road test the vehicle 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

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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

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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 Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.