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B2A2213

DTC B2A2213 indicates an open circuit fault in the Ambient Temperature Sensor circuit — Seal U

Thermal Management System

DTC B2A2213 indicates an open circuit fault in the Ambient Temperature Sensor circuit.

Typically an NTC (Negative Temperature Coefficient) thermistor installed near the front bumper or side mirror, this sensor monitors ambient temperature in real time and sends a feedback signal to the HVAC ECU.

The controller logs an open circuit if it detects the sensor signal voltage remaining continuously high (typically the undivided 5V reference voltage, representing an open circuit) beyond the set threshold (generally 2–5 seconds).

This fault prevents the automatic air conditioning system from accurately calculating the target outlet air temperature.

It affects compressor start-stop control, PTC heater power regulation, fresh/recirculated air switching logic, and battery thermal management strategies (such as low-temperature charging preheating and high-temperature cooling activation).

In extreme cases, the system triggers thermal management derating protection and limits motor power output to protect the high-voltage powertrain.

Therefore, the system classifies this as a severe fault.

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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Internal open circuit or resistance drift in the ambient temperature sensor (thermistor open circuit caused by impact cracking or water ingress from seal failure).
  • 2Backed-out terminals, oxidation, or poor contact at the sensor harness connector (common after water ingress into the front compartment, high-pressure washing, or prolonged salt spray exposure)
  • 3Physical open circuit in the signal wiring harness from the sensor to the air conditioning controller (high engine compartment temperatures causing insulation embrittlement and breakage, or a poor connection at the firewall pass-through connector)
  • 4A/C controller internal signal sampling circuit fault (electrostatic breakdown, cold solder joints, or loose connector causing a floating sampling terminal)
  • 5Loose sensor mounting bracket causes long-term bending and fatigue fracture of the wiring harness (especially mechanical fatigue after driving on rough roads).
What To Do
  • 1
    Visual inspection: Verify the ambient temperature sensor has no damage or cracks, mounts in the correct position unobstructed, and the wiring harness sleeve shows no mechanical damage or heat melting marks.
  • 2
    Sensor body measurement: Disconnect the sensor connector. Use a multimeter to measure the resistance between the two sensor terminals (standard value at 25°C is approx. 2.0-2.5kΩ; resistance decreases non-linearly as temperature rises). If the resistance is infinite, replace the sensor.
  • 3
    Circuit continuity test: Use a multimeter continuity buzzer to measure the continuity of the signal wire (usually the center pin) and ground wire between the sensor connector and the air conditioning controller. Inspect the front compartment firewall intermediate connectors (such as BJA01, B2A01) for oxidized, backed-out, or enlarged terminals.
  • 4
    Voltage and signal verification: Connect the sensor. With power ON, measure the voltage between the signal wire and ground (normal range: 0.5-4.5V, varying with ambient temperature). A constant 5V confirms an open circuit. Short the sensor connector to simulate a short circuit and observe if the fault code changes to B2A2311 (short circuit code) to locate the faulty section.
  • 5
    Controller and software check: After ruling out wiring and sensor faults, use the VDS2000 diagnostic tool to check the air conditioning controller software version. Some early versions contain signal sampling algorithm defects and require an update to the latest version. Replace the air conditioning controller assembly if necessary.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM: Sudden A/C Failure with Communication Fault

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Symptoms: AC quit cooling while driving; vents blew ambient air. The temp display on the control panel showed abnormal values, and the system intermittently recovered after a restart. Diagnosis: Connected VDS2000 and read DTC B2A2213 (AC compressor control circuit open). Checked the electric compressor controller power supply fuse F1/14 in the front compartment — normal. Measured constant power at controller plug pin 1: 12.4V (normal). Pin 3 had continuity to ground (normal). Checked CAN bus communication: pin 5 CAN-H measured 0V (normal 2.5–3.5V). Traced the harness and found pin 18 of the BJA01 connector at the front firewall oxidized, causing poor contact. Resolution: Cleaned the BJA01 connector pins with electrical contact cleaner and applied conductive grease. Reconnected the plug and secured the harness with cable ties to prevent movement. Cleared the DTCs and test-drove 50 km; the fault did not return.
Original source ↗
BYD DTC AI Analysis

Song PLUS DM-i AC fault after fast charging

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Symptoms: Air conditioning failed to start after DC fast charging. The AC button was unresponsive and the dash displayed "Air Conditioning System Fault." The fault appeared every time the vehicle connected to a charging station. Diagnosis: Scanned DTCs B2A2213 and U016487 (lost communication with HVAC controller). Checked the high-voltage distribution box and measured the electric compressor high-voltage interlock loop, finding abnormal 12V signal on the interlock line. Analyzed live data and found that during fast charging, the BMS prioritizes limiting air conditioning power, but the compressor controller software version V1.2 failed to respond correctly to the power reduction command, causing a communication timeout. Fix: Upgraded the electric compressor controller software to version V1.5 using the BYD dedicated diagnostic tool (online programming). Also inspected high-voltage wiring harness connections. After the update, fast-charging logic worked normally and the air conditioning automatically stopped and started as power was adjusted.
Original source ↗
BYD DTC AI Analysis

Tang DM control fault following compressor noise

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Symptoms: Turned on the air conditioning and heard a buzzing noise lasting ~10 seconds before disappearing. The air conditioning then stopped cooling. Restarted the vehicle and the air conditioning did not operate at all. Scanned DTC B2A2213. Diagnosis: Initial inspection found the compressor mechanically seized. Disassembly confirmed the internal motor windings burned out, tripping controller overcurrent protection. Measured the compressor controller output terminals and found a short to ground. Further inspection revealed the IGBT module inside the controller failed. Traced the root cause to a previous repair at an independent shop that overcharged the refrigerant, overloading and burning out the compressor. Resolution: Replaced the electric compressor assembly (including controller). Refilled with R134a refrigerant and PAG oil strictly to the standard charge of 650g±25g. Thoroughly cleaned the air conditioning lines before replacement to prevent debris from damaging the new compressor.
Original source ↗
BYD DTC AI Analysis

e5 taxi intermittent AC failure

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Symptoms: The air conditioning randomly cut out during taxi operations, particularly under high ambient temperatures and heavy loads. When the fault occurred the instrument cluster showed no display, but cycling the ignition restored operation. Fault code B2A2213 stored as a history code. Diagnosis: Reproduced the fault by heating the compressor controller connector with a heat gun to simulate high-temperature conditions. Measured the controller supply line and found the 12V feed dropped to 3V at the moment of failure, indicating high resistance. Inspected the power wiring from the fuse box to the compressor and found the insulation had been damaged during a previous GPS installation, causing intermittent shorting under heat. Measured CAN bus termination resistance at 120 Ω (normal), ruling out network faults. Resolution: Repaired the damaged power wiring harness (re-soldered and sealed with heat-shrink tubing). Relocated the GPS power feed to downstream of the ACC relay to prevent interference with the compressor high-current circuit. Applied waterproof tape to the compressor controller connector to protect against engine bay heat.
Original source ↗
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.