AU
B2A5A11

This DTC indicates a short to ground in the signal circuit of the front passenger side FACE mode outlet air temperature sensor — Atto 3

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.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1The internal thermistor of the temperature sensor breaks down and short-circuits, connecting the signal terminal directly to ground.
  • 2Damaged wiring harness insulation inside the right dashboard A/C 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 ingress, causing a short circuit between pins or a short to ground.
  • 4A detached wiring harness retaining clip causes the harness to chafe against the instrument panel frame while driving, resulting in long-term damage.
  • 5Improper 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 in the freeze frame data.
  • 2
    Remove the passenger-side lower dash trim panel and locate the face vent temperature sensor (usually inside the right HVAC assembly air outlet duct). Disconnect the connector and measure the sensor resistance: at 20°C, it must be 1.8-2.2 kΩ. A reading of 0-10 Ω indicates an internal short circuit. Replace the sensor.
  • 3
    Keep the connector disconnected. Use a multimeter to measure the resistance between the harness-side signal pin (usually the yellow wire) and body ground. Normal resistance exceeds 10MΩ. If continuity exists, inspect the wiring harness routing for damage, focusing on sharp edges at the firewall and instrument panel bracket.
  • 4
    Check connector seal ring integrity. Inspect pins for oxidation, verdigris, or water stains. If necessary, clean with electronic contact cleaner and spray WD-40 for waterproofing. Replace the connector if severely corroded.
  • 5
    If the wiring harness appears normal but a short to ground exists, use the sectional isolation method: disconnect the intermediate connector and measure the insulation of the front and rear harness sections separately to isolate the fault to a specific wire segment.
  • 6
    Check the air conditioning controller side: Disconnect the controller connector and measure the resistance from the corresponding pin to ground to confirm the controller has no internal short circuit (very rare).
  • 7
    After repairing or replacing the faulty wiring harness or sensor, restore 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. Monitor the data stream to verify the 'front passenger face vent temperature' reads normally (the temperature should gradually decrease with airflow). Confirm 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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.