AU
B2A5A11

This DTC indicates a short to ground in the signal circuit of the front passenger side FACE mode outlet air temperature sensor — Seal 6 EV

Thermal Management System

This DTC indicates a short to ground in the signal circuit of the front passenger side FACE mode outlet air temperature sensor.

In the BYD dual-zone automatic air conditioning system, this sensor uses an NTC (negative temperature coefficient) thermistor.

Under normal conditions, sensor resistance decreases as temperature increases (approximately 2 kΩ at 20°C).

The air conditioning controller calculates the actual outlet air temperature by detecting the voltage signal (typically in the 0-5 V range) through a voltage divider circuit.

When the signal wire shorts to the vehicle body ground, the controller detects a continuous voltage below 0.1 V (or close to 0 V) and sets DTC B2A5A11.

This disables the front passenger side temperature control.

The air conditioning system may enter limp mode and default to a fixed output temperature, reducing passenger comfort.

In extreme cases, false readings may trigger thermal management system protection.

The B2A5A11 fault code on the Seal 6 EV indicates a high-severity short to ground in the front passenger FACE mode outlet air temperature sensor signal circuit. This can disable passenger-side temperature control or trigger limp mode. Common causes include an internal sensor short or damaged dashboard duct wiring contacting metal. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1A breakdown and short circuit of the thermistor inside the temperature sensor body directly grounds the signal terminal.
  • 2Damaged wiring harness insulation inside the right dashboard air conditioning duct causes the signal wire to contact the metal duct or a sharp body edge and short to ground.
  • 3Poor sensor connector sealing allows A/C condensate to seep in, causing a short circuit between pins or a short to ground.
  • 4Detached wiring harness retaining clip allows the harness to rub against the instrument panel frame during driving, causing chafing damage over time.
  • 5Incorrect wiring harness routing after previous repairs caused the instrument panel trim to pinch the harness and pierce the insulation.
What To Do
  • 1
    Connect the VDS2000 or BYD dedicated diagnostic tool, read the fault code to confirm B2A5A11 is a Current fault, and record the ambient temperature value from the freeze frame data.
  • 2
    Remove the passenger-side lower dashboard trim panel and locate the face vent temperature sensor (usually inside the right HVAC assembly outlet duct). Disconnect the connector and measure the sensor resistance: at 20°C it should be 1.8-2.2kΩ. If it reads 0-10Ω, the sensor has an internal short circuit. Replace the sensor.
  • 3
    Leave the connector disconnected. Use a multimeter to measure the resistance between the harness-side signal pin (usually the yellow wire) and body ground. The resistance must exceed 10 MΩ. If continuity exists, inspect the wiring harness along its routing for damage. Focus on sharp edges, such as where the harness passes through the firewall and the instrument panel bracket.
  • 4
    Check connector seal ring integrity. Inspect pins for oxidation, verdigris, or water marks. If necessary, clean with electrical contact cleaner and spray WD-40 for waterproofing. Replace the connector if severely corroded.
  • 5
    If the wiring harness appears normal but is shorted to ground, use the sectional isolation method: disconnect the intermediate connector and measure the insulation of the front and rear harness sections separately to isolate the faulty wire segment.
  • 6
    Check the air conditioning controller side: disconnect the controller connector and measure the resistance from the corresponding pin to ground to rule out an internal short circuit in the controller (very rare).
  • 7
    After repairing or replacing the faulty wiring harness or sensor, restore the connections and clear the fault code. Start the vehicle and turn on the air conditioning (set to 22°C, face mode). Run the system for 15 minutes and monitor the 'front passenger face vent temperature' in the data stream. The temperature must gradually decrease with airflow. Verify the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

2018 BYD Song MAX: Sensor Short Circuit from Water Ingress

✓
After heavy rain while parked outdoors, the passenger side A/C vents blew icy cold air and wouldn't adjust. The scanner showed active DTC B2A5A11. Sensor resistance measured 0.5Ω (shorted). Disassembly revealed the sensor mounted at the lowest point of the air duct. A blocked drain hole caused condensate to accumulate, completely submerging the connector and shorting the pins. Fix: Cleared the A/C drain tube, replaced the passenger face-level temperature sensor, dried the connector and applied anti-corrosion treatment. Fault cleared.
BYD DTC AI Analysis

2019 BYD Qin Pro DM Dashboard Wiring Harness Wear Case

✓
When driving on rough roads, the AC panel occasionally displayed an 'E3' error, eventually triggering DTC B2A5A11. Static sensor tests showed normal readings, but resistance to ground fluctuated when wiggling the harness. Removed the dashboard and found the harness retaining clip had fallen off where it passes through the metal bracket. Long-term rubbing against the sharp edge wore through 3 mm of insulation, exposing the copper core to the body. Repaired the wiring by soldering and adding heat-shrink tubing, re-secured the harness with a rubber grommet, and adjusted the routing to avoid interference.
BYD DTC AI Analysis

2019 Qin EV Sensor Aging Failure Case

✓
After 4 years, the passenger-side temperature display stuck at -40°C (ultra-low) with intermittent DTC B2A5A11. Sensor resistance measured only 50Ω at ambient temperature (normal: 2kΩ), indicating internal thermistor breakdown from aging. Harness insulation tested normal and connectors showed no water ingress. Replaced the OEM passenger-side face-level air temperature sensor (Part No.: EG-8107010B). Temperature display returned to normal; fault code cleared and has not returned.
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.