AU
B2A3214

This DTC indicates the air conditioning control unit (ACU) or thermal management controller detects an abnormal electrical condition in the front HVAC blower motor power supply circuit, specifically a short to body ground (impedance <1Ω) or an open circuit/high resistance (impedance >10kΩ) — Atto 3

Thermal Management System

This DTC indicates the air conditioning control unit (ACU) or thermal management controller detects an abnormal electrical condition in the front HVAC blower motor power supply circuit, specifically a short to body ground (impedance <1Ω) or an open circuit/high resistance (impedance >10kΩ).

In the BYD e-platform architecture, a PWM (pulse-width modulation) or LIN bus communication speed control module typically controls the blower motor.

The ACU determines the circuit status by monitoring the blower motor current or feedback signal.

The ACU triggers this DTC when it detects sustained high current (short circuit) or zero current (open circuit) exceeding the calibrated threshold (typically 200ms-1s).

This fault prevents the front HVAC module from supplying air and affects cabin temperature regulation.

In extreme cases, a short circuit can overheat the wiring harness and trigger the high-voltage interlock protection.

The B2A3214 fault code on the Atto 3 indicates a high-severity fault in the front HVAC blower motor power supply circuit, usually a short to ground or an open/high-resistance circuit. Common causes include a burnt or worn blower motor, or damaged wiring insulation chafing against body metal near the firewall. The front air supply may stop working. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Burnt blower motor internal windings or worn commutator causing a short circuit to the housing. Common in vehicles over 3 years old or vehicles operating the air conditioning under prolonged high load.
  • 2Instrument panel wiring harness insulation chafes at the firewall pass-through hole and contacts body metal, causing a short to ground. Assembly processes or vibration typically cause this.
  • 3An internal power transistor in the blower speed control module (Power Transistor) breaks down and short-circuits, causing the ACU to detect an abnormally high current.
  • 4Water ingress and corrosion at the power supply line connector from the front compartment power distribution box to the blower motor (usually inside the passenger-side dashboard), causing an intermittent open circuit or short to ground; this often occurs with a blocked air conditioning drain hose.
  • 5Air conditioning controller internal drive circuit fault or abnormal software calibration outputting an incorrect diagnostic signal.
What To Do
  • 1
    Safety preparation: Wear insulated gloves, disconnect the high-voltage service disconnect (MSD), wait 5 minutes for the high-voltage capacitors to fully discharge, and disconnect the 12V battery negative terminal.
  • 2
    Fault confirmation: Use the VDS2000 or DiLink diagnostic tool to read all DTCs. Check for accompanying fault codes (such as B2A3314 speed control signal fault) and record the current value in the freeze frame data.
  • 3
    Power supply check: Check if the air conditioning system fuse in the front compartment fuse box (usually F2/10A or blower fuse 20A) is blown. Measure the voltage at the blower power supply terminal (should be 12V/B+ with the key in the ON position).
  • 4
    Circuit continuity test: Disconnect the blower connector (usually located above the front passenger footwell). Measure resistance to ground on the wiring harness side (normal: >1 MΩ; short circuit: <1 Ω). Measure continuity from the wiring harness terminal to the ACU terminal (<1 Ω).
  • 5
    Component inspection: Measure the blower motor resistance (normal: 2-5 Ω; short circuit: <1 Ω; open circuit: infinite). Check the waveform at the blower speed control module output terminal (PWM signal duty cycle must vary from 0-100% with fan speed adjustment).
  • 6
    Insulation test: Use a megohmmeter (500V setting) to measure the insulation resistance between the blower power supply wire and the vehicle body (should be >20 MΩ) and check for hidden short circuits.
  • 7
    Repair/Replacement: Replace the damaged blower assembly or speed control module, or repair the wiring harness (insulate with heat-shrink tubing). Apply conductive paste to the connector to prevent corrosion.
  • 8
    Verification test: Reconnect all components and clear the fault code. Power on the vehicle and test each fan speed setting (levels 1-7 or AUTO mode). Confirm normal current draw (typically 3-15A, varying with speed). Monitor continuously for 10 minutes to verify the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

Song MAX blower motor intermittent stoppage (short to ground)

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Symptoms: Air conditioning suddenly stopped blowing while driving a 2018 Song MAX. The instrument cluster displayed an AC fault, with intermittent recovery after restarting. Diagnosis: Connected VDS and retrieved DTC B2A3214. Measured the blower motor power feed during rough-road testing and found ground resistance fluctuating between 0-5Ω. Inspection revealed the firewall harness insulation was cut through by a sharp metal bracket edge. Fix: Repaired the damaged harness (fitted corrugated tubing and heat-shrink sleeving), rerouted the harness to avoid interference, and replaced the blower fuse. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro EV blower motor burned out (internal short circuit)

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Symptoms: 2019 Qin Pro EV blows AC fuse at max blower speed; replacement fuse blows instantly. Diagnosis: Disconnecting the blower motor connector stops the fuse from blowing. Measured 0.3Ω between motor terminals and housing (severe short to ground). Disassembled the motor: commutator heavily carboned, windings burned. Resolution: Replaced front blower motor assembly (PN: TA-8103010). Cleaned AC evaporator (dust from motor burnout). Replaced speed control module (possibly damaged by long-term overload).
Original source ↗
BYD DTC AI Analysis

Qin EV speed control module fault causes false open circuit

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Symptoms: 2017 Qin EV climate control panel displays normally but the blower does not run. Scan tool reports B2A3214 open-circuit fault. Diagnosis: Powered the blower motor directly—it ran normally, ruling out motor failure. Input voltage at the speed control module (located under the blower) was normal, but output had no voltage. LIN bus communication was normal. Determined the module’s internal MOSFET had failed open-circuit. Solution: Replaced the blower speed control module (PWM Controller), programmed and matched it. Fault cleared. This case shows that "open circuit" in the fault code can indicate an internal open in the speed control module rather than a wiring fault.
BYD DTC AI Analysis

Song MAX connector water ingress and corrosion (intermittent fault)

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Symptoms: 2019 Song MAX AC automatically shut down frequently during rainy season but operated normally on sunny days. Fault code B2A3214 intermittent. Diagnosis: Passenger-side floor was damp. Blocked AC drain hose caused condensate overflow. The blower power connector (white 6-pin) had severely oxidised (green) internal pins; contact resistance exceeded 10 Ω, producing a false open-circuit fault. Resolution: Cleared the drain hose, cleaned the connector pins with electrical contact cleaner, applied dielectric grease, and replaced the connector housing where necessary.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.