AU
B2A2413

DTC B2A2413 indicates the air conditioning control unit (AC ECU) detects an open circuit in the evaporator temperature sensor circuit — Seal U

Thermal Management System

DTC B2A2413 indicates the air conditioning control unit (AC ECU) detects an open circuit in the evaporator temperature sensor circuit.

This sensor, typically a negative temperature coefficient (NTC) thermistor, mounts to the evaporator fin surface inside the HVAC assembly.

It monitors real-time evaporator core temperature (normal operating range: 2–8°C).

If the sensor fails open, the wiring harness disconnects, or the connector has poor contact, the ECU detects a continuous 5V signal (or open-circuit voltage) and cannot obtain accurate evaporator temperature data.

The system then triggers a protection strategy.

To prevent evaporator icing, expansion, and core damage, the ECU forcibly disengages the compressor electromagnetic clutch or disables the electric compressor.

It may also default to a substitute value (such as 0°C or ambient temperature) to maintain limited cooling.

This causes air conditioning performance to degrade severely or fail completely.

Prolonged operation with this fault can cause frequent compressor cycling, abnormal battery pack thermal management (on models where the air conditioning system couples with battery cooling), and even high-voltage system insulation faults.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Internal open circuit in the evaporator temperature sensor: Prolonged exposure to low temperatures and high humidity causes the internal thermistor element to age and crack, or the package seal to fail, resulting in moisture ingress, corrosion, and an open circuit.
  • 2Loose harness connector or backed-out terminal: Prolonged driving on rough roads causes the sensor plug (usually a 2-pin white connector) on the passenger-side dashboard HVAC assembly to loosen, the locking tab to break, or the terminal to back out, resulting in poor contact.
  • 3Physical wiring harness damage: Metal edges cut the internal dashboard wiring harness during assembly or repair, or rodents chew through the signal wire (the relatively quiet motor compartment in EV models attracts rodents to chew the wiring harness).
  • 4Pin corrosion: Operating the vehicle in coastal or high-humidity areas degrades the sensor plug sealing ring. Moisture intrusion oxidizes the copper pins, forming green corrosion and causing a high-resistance open circuit.
  • 5Air conditioning controller internal sampling circuit fault: cold solder joints at the controller terminals or a damaged internal pull-up resistor prevents correct sensor signal recognition (rule out the first four items before confirming this diagnosis).
What To Do
  • 1
    Connect the VDS2000/Launch X431 diagnostic tool, access the air conditioning system to read fault codes, and confirm B2A2413 is a Current DTC. Record the Freeze Frame data and observe the ambient temperature and system status when the fault occurred.
  • 2
    Remove the front passenger glovebox or lower trim panel. Locate the evaporator temperature sensor (positioned between the fins on the right side of the evaporator core, usually with a black plastic housing and a 2-wire connector). Visually inspect the connector for looseness and the wiring harness for damage.
  • 3
    Disconnect the sensor connector and use a multimeter to measure the resistance between the two sensor terminals. At an ambient temperature of 25°C, the normal value is approximately 2.0-2.5 kΩ (refer to the temperature-resistance curve table in the workshop manual for specific values). If the multimeter reads OL (open circuit) or the resistance significantly exceeds the nominal value, replace the sensor assembly.
  • 4
    If the sensor resistance is normal, measure at the wiring harness connector: Set the ignition switch to ON. Measure the voltage between the signal wire and ground wire; it should be the 5V reference voltage. Turn the ignition switch OFF. Measure the continuity from the sensor connector to the corresponding pin of the air conditioning controller. The resistance should be less than 1Ω. If there is no continuity, inspect the wiring harness in sections to locate the break.
  • 5
    Check the sensor connector pins for oxidation, terminal spread, or bent pins. If necessary, clean the pins with electrical contact cleaner and restore pin tension. Apply conductive grease and reconnect the plug. Ensure the locking tab clicks fully into place.
  • 6
    If the wiring harness and sensor are normal, remove the air conditioning controller. Inspect the corresponding controller terminals (usually specific pins in the B23 or B24 connector) for dry solder joints or corrosion. Replace the controller assembly if necessary.
  • 7
    After repair, clear the fault code. Start the vehicle and set the air conditioning to maximum cooling mode. Monitor the data stream to verify the evaporator temperature gradually drops from ambient temperature to 2-5°C during the cooling process. Confirm no icing occurs and the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

Atto 3 air conditioning not cooling with fault code B2A2413

✓
2022 BYD Atto3 (Yuan Plus), 12,000 km. With the AC on, the vents blew only ambient air. No dashboard warnings appeared, but cooling failed. A scan tool showed current fault code B2A2413 (evaporator temperature sensor open circuit). Removing the passenger-side glovebox revealed the evaporator temperature sensor connector lock tab had broken; the connector worked loose and interrupted the signal. Without a temperature signal, the ECU entered protection mode and shut down the electric compressor. Re-securing the connector and reinforcing the wiring harness with cable ties restored operation: the data stream showed evaporator temperature dropping from 35°C to 4°C, and cooling returned to normal.
Original source ↗
BYD DTC AI Analysis

Qin Pro DM evaporator icing and low-pressure line frosting

✓
2019 BYD Qin Pro DM, 30,000 km. Owner reported AC cooling dropped sharply after 10 minutes. Found severe frost on the low-pressure line. Initially suspected a faulty expansion valve, but the scan showed intermittent DTC B2A2413. Inspection revealed the sensor harness chafed through at the firewall by a retaining clip. 80% of the internal copper wires had broken, leaving only a few strands connected and causing an intermittent open. When the signal interrupted, the ECU could not detect the evaporator had dropped below 0°C, so the compressor kept running and iced up the system. Repaired the harness and fitted a protective sleeve. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Rodents chewed through wiring inside the dashboard of a Song MAX, causing a sensor open circuit.

✓
A 2018 Song MAX was parked for one week. At startup, the AC failed to cool and emitted a slight odor. The scan tool reported B2A2413 and B2A2011 (sunlight sensor faults, same harness branch). Removed the dashboard to inspect the HVAC assembly and found rodents had chewed through multiple wires in the evaporator temperature sensor and sunlight sensor harnesses above the blower motor; the evaporator temperature sensor signal wire was completely severed. Cleaned up the wiring debris, re-ran new wires from the root with corrugated tubing, replaced the damaged sensors, and performed the AC system self-learning procedure using VDS (some models require zone matching). Fault resolved.
BYD DTC AI Analysis

Qin EV300 sensor pin corrosion caused intermittent open circuit

✓
A 2017 Qin EV300 used in a coastal area had intermittent AC cooling failure. DTC B2A2413 stored as a history code, occurring mainly on cold startup. Inspection found the evaporator temperature sensor connector pins covered in green copper corrosion. The connector seal had aged, letting salt spray from sea breezes intrude and corrode the terminals. Static testing sometimes showed continuity, but driving vibration increased contact resistance, causing the ECU to misinterpret the signal as an open circuit. Cleaned the pins with WD-40 Precision Electrical Contact Cleaner, applied dielectric grease, and replaced the connector with a new sealed unit. No recurrence after one month of monitoring.
Other Seal U 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.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.
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.