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) — Seal U

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 Seal U indicates a high-severity electrical fault in the front HVAC blower motor power supply circuit, caused by a short to body ground or an open/high-resistance circuit. This can stop cabin airflow and affect temperature control. Common causes include a burnt blower motor winding or chafed instrument panel wiring near the firewall. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Burnt blower motor internal winding or worn commutator causing a short circuit to the housing. Common in vehicles over 3 years old or subject to prolonged high-load air conditioning operation.
  • 2Instrument panel wiring harness insulation chafes at the firewall pass-through hole, contacting body metal and causing a short to ground, typically due to assembly issues or vibration.
  • 3The 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 circuit connector from the front compartment power distribution box to the blower motor (usually located inside the passenger-side dashboard) causes an intermittent open circuit or short to ground. A blocked air conditioning drain hose often accompanies this fault.
  • 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 manual service disconnect (MSD), wait 5 minutes for the high-voltage capacitors to discharge completely, 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 power distribution 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 above the front passenger footwell), measure resistance to ground on the wiring harness side (normal: >1 MΩ; short circuit: <1 Ω), and 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 speed control module output terminal (PWM signal duty cycle should vary between 0–100% with fan speed adjustment).
  • 6
    Insulation test: Use a megohmmeter (500V range) to measure the insulation resistance between the blower power supply wire and the vehicle body (must be >20MΩ) to locate hidden short circuits.
  • 7
    Repair/Replace: 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. Clear the fault code. Power on and test each fan speed setting (levels 1-7 or AUTO mode). Confirm normal current draw (typically 3-15A, varying with fan speed). Observe for 10 minutes to confirm the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

Song MAX blower motor intermittent stoppage (short to ground)

✓
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)

✓
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

✓
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)

✓
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 Seal U Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.