AU
B2A2013

BYD technical documentation defines DTC B2A2013 as "Evaporator Temperature Sensor Circuit Open," rather than a generic "cabin temperature sensor" fault — Atto 3

Thermal Management System

BYD technical documentation defines DTC B2A2013 as "Evaporator Temperature Sensor Circuit Open," rather than a generic "cabin temperature sensor" fault.

Located inside the HVAC evaporator case, this sensor monitors the evaporator core surface temperature in real time.

It sends critical feedback to the air conditioning controller (AC ECU) to prevent evaporator icing, regulate compressor displacement, and control the electronic expansion valve opening.

The AC ECU logs an open circuit fault when it detects the sensor signal voltage remaining above 4.95V or below 0.05V (outside the valid range).

This fault triggers the A/C system protection logic, which forcibly disengages the compressor electromagnetic clutch or stops the electric compressor, completely disabling A/C cooling.

Because BYD New Energy Vehicles (NEVs) deeply integrate the A/C and battery thermal management systems (typically incorporating the battery chiller into the A/C refrigerant circuit), this fault can cascade into a battery cooling system failure.

This causes abnormal vehicle thermal management and may restrict power output.

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Cases Logged
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Causes
Likely Causes — Atto 3
  • 1Internal open circuit in the evaporator temperature sensor or thermistor characteristic drift, preventing the sensor from generating a valid temperature-resistance signal.
  • 2Sensor wiring harness wear, breakage, or crush damage at stress concentration points such as the firewall wiring grommet and instrument panel frame mounting points.
  • 3Oxidation, corrosion, or poor contact at the sensor connector plug pins due to evaporator case condensate leakage, floor water ingress, or leaks during car washing.
  • 4Loose wiring harness retaining clip causes vibration during driving. Prolonged tension breaks the wire at the base of the connector (intermittent open circuit).
  • 5Fault in the air conditioning controller internal signal sampling circuit (such as an open voltage divider resistor or shorted filter capacitor), preventing the controller from correctly identifying the sensor signal.
What To Do
  • 1
    Use a dedicated diagnostic tool (such as VDS2000 or Launch X-431) to read air conditioning system fault codes, confirm B2A2013 is present, and record freeze frame data (abnormal ambient and evaporator temperature values are typically -40℃ or a fixed high value).
  • 2
    Enter data stream mode and monitor the 'Evaporator Temperature Sensor' value in real time. After turning on the air conditioning, if the value does not change or remains at an extreme value (-40°C/120°C), confirm an abnormal signal.
  • 3
    Remove the front passenger side glove box or lower dashboard trim panel and locate the evaporator temperature sensor (usually a two-wire NTC thermistor located on the evaporator housing). Visually inspect the connector for looseness, water ingress, or signs of corrosion.
  • 4
    Disconnect the connector and measure the sensor resistance. At 25°C ambient temperature, the standard value is 1.8-2.5 kΩ. Warm the sensor by hand; the resistance must decrease as temperature rises (negative temperature coefficient characteristic). If the resistance is infinite or does not change, replace the sensor.
  • 5
    Measure harness-side voltage: With the ignition switch ON and the connector disconnected, verify the harness terminal has a 5V reference voltage (supplied by the AC ECU) and a ground circuit. If the voltage is 0V or 12V, check the power supply and ground wiring.
  • 6
    Measure wiring harness continuity between the sensor and the AC ECU using a multimeter set to resistance. Standard resistance must be less than 1 Ω. Inspect the firewall wiring grommet and floor wiring harness sleeve bends. Repair any open circuits and install a wear-resistant protective sleeve.
  • 7
    If the wiring harness and sensor are normal, measure continuity between the corresponding AC ECU pin and the sensor. If the ECU side does not output a 5V reference voltage, this indicates an internal fault in the air conditioning controller. Replace or repair the controller.
  • 8
    After completing the repair, reconnect all connectors, clear the fault code, and run the 'Air Conditioning System Self-Diagnosis' or 'Component Test' function to confirm the evaporator temperature data stream returns to normal (typically 2-10°C depending on operating conditions).
  • 9
    Perform a 30-minute road test to verify if the fault code reappears. Check the A/C cooling performance and verify normal coordinated operation of the battery cooling system.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV300 AC not cooling — oxidized connector causing intermittent open circuit

✓
2017 Qin EV300, 60,000 km. Owner reported the A/C suddenly stopped cooling, blowing ambient air. Scan tool showed DTC B2A2013 (evaporator temperature sensor circuit open) and B2A2111. Live data indicated evaporator temperature at -40°C (abnormal). Removed the glove box and found the evaporator temperature sensor connector loose with green oxidation on the pins. Measured sensor resistance at 2.1kΩ—normal—but the loose connection interrupted the signal. Cleaned the connector with electronic cleaner, polished the pins with fine sandpaper, applied conductive grease, and resecured the plug. Cleared the fault codes. Evaporator temperature now read 8°C, the compressor clutch engaged normally, and cooling was restored.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM intermittent AC shutdown – sensor corroded by condensate

✓
A 2018 BYD Tang DM had intermittent AC cooling that suddenly cut out while driving, occasionally recovering after restart. DTC B2A2013 set intermittently. Live data showed evaporator temperature jumping between -40°C and actual values. Removing the evaporator housing revealed condensate pooling at the temperature sensor mounting hole; the sensor pins had corroded and blackened. Further inspection found the evaporator drain hole blocked with dust, causing condensate to accumulate and continuously soak the sensor. Cleared the drain hole, replaced the evaporator temperature sensor assembly, and applied waterproof sealant to the connector. Monitored for one month with no recurrence.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro EV compressor not working — firewall wiring harness chafed through, open circuit

✓
A 2019 Song Pro EV had no cold air with the AC on; the compressor clutch did not engage. DTCs B2A2013 and B2A2A14 present. Evaporator temperature sensor supply measured 5V (normal), but the signal line measured 4.98V (close to reference voltage, indicating an open circuit). Traced the wiring and found the harness rubbing against a sharp metal edge at the firewall grommet; insulation was damaged and the wire broken. Cut out the damaged section, soldered the connection, insulated with heat-shrink tubing, rerouted the wiring, and added a rubber sleeve to prevent further chafing. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Water in BYD Han EV floor corroded sensor connector

✓
A 2020 Han EV came in with the AC not cooling and the battery cooling system warning light on. The scan tool read DTC B2A2013 from the air conditioning system and a cooling system fault from the BMS. Inspection found water ingress at the wiring harness connector under the passenger floor; the evaporator temperature sensor connector pins had corroded and broken. Traced the source to a perished front windscreen seal letting rainwater into the floor. Replaced the corroded harness connector, dried the harness, repaired the seal, and raised the connector mounting position to keep it clear of standing water. Bled the battery cooling system and calibrated the AC.
Original source ↗
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.