AU
B2AB349

This DTC indicates an abnormal signal or functional failure of the temperature sensor integrated inside the Electric A/C Compressor — Atto 8

Thermal Management System

This DTC indicates an abnormal signal or functional failure of the temperature sensor integrated inside the Electric A/C Compressor.

This sensor is embedded near the compressor motor winding or power module (IPM).

It monitors the operating temperature of the compressor core components in real time to prevent motor demagnetization or controller damage from overheating.

When the sensor experiences an open circuit, short circuit, signal drift, or detects a value outside the normal threshold (-40°C to 150°C), the compressor controller triggers DTC B2AB349 and enters protection mode, forcibly cutting operating power to the compressor.

This fault directly causes the air conditioning system to lose cooling capacity.

In extreme cases, the lack of cooling may indirectly affect the traction battery thermal management circuit, but it typically does not limit vehicle power.

3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Compressor internal temperature sensor damaged, or thermistor resistance drift (due to long-term high-temperature aging or refrigerant chemical corrosion).
  • 2Temperature signal acquisition circuit fault on the compressor controller PCB (e.g., burnt sampling resistor, failed filter capacitor, or cold solder joint)
  • 3Open circuit in the compressor internal temperature sensor wiring harness, or poor connector contact (due to continuous compressor vibration)
  • 4Severely low system refrigerant or poor refrigerant oil lubrication causes the compressor to overheat, triggering the sensor over-temperature protection threshold.
  • 5Strong external electromagnetic interference or high-voltage system transient surges cause abnormal sensor signals (e.g., interference from an insulation fault).
What To Do
  • 1
    Scan the entire vehicle system using VDS2000 or the latest diagnostic tool. Verify B2AB349 is a current fault that does not clear, and record the freeze frame data.
  • 2
    Read the air conditioning system data stream and check if the displayed 'compressor internal temperature' value is abnormal (e.g., displays -40°C, 150°C, or significantly deviates from ambient temperature).
  • 3
    Disconnect the compressor low-voltage 12V control connector. Measure the temperature sensor resistance with a multimeter (refer to the workshop manual; typically approx. 2kΩ-10kΩ at 25°C) to check if the sensor itself is damaged.
  • 4
    Check the low-voltage wiring harness connector for water ingress, corrosion, terminal back-out, or poor contact. Measure the continuity and insulation resistance of the wiring between the connector and the controller (insulation resistance must be greater than 1MΩ).
  • 5
    Check the high-voltage interlock loop (HVIL) continuity and compressor high-voltage power supply (DC high voltage) for normal operation to rule out cascading faults in the high-voltage system.
  • 6
    If the sensor and external wiring are normal but the fault persists, the compressor internal control board is faulty. Replace the compressor assembly.
  • 7
    Use a refrigerant recovery machine to recover R134a or R1234yf refrigerant, then remove and replace the electric compressor assembly (the internal sensor is not serviced separately).
  • 8
    Simultaneously replace the desiccant/receiver drier. Add POE refrigerant oil (usually 40-80 ml, depending on vehicle model) and the specified amount of refrigerant per repair manual specifications.
  • 9
    After assembly, perform a system pressure hold leak test and evacuate the system (for at least 30 minutes). Run the compressor initialization learning procedure (such as 'Compressor Zero Position Calibration' in VDS), and perform an air conditioning performance test.
Real-World Cases
BYD DTC AI Analysis

BYD Yuan Plus: Sudden AC Cooling Failure

✓
The air conditioning suddenly stopped cooling during normal driving. No warning lights appeared on the dash, but the vents blew ambient air. A VDS scan retrieved DTC B2AB349 (internal temperature sensor fault). Live data showed the compressor internal temperature at -40°C (clearly abnormal), indicating an open circuit in the sensor. Resistance across the temperature sensor pins at the compressor low-pressure connector measured infinite, confirming sensor failure. Since the sensor is integrated inside the compressor and cannot be replaced separately, the fix involved replacing the electric compressor assembly, recharging the refrigerant and refilling the compressor oil. This resolved the fault.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV Intermittent Air Conditioning Failure Case

✓
AC intermittently cuts out in hot weather or after extended use, returning to normal after a key cycle. Retrieved DTC B2AB349. Live data showed compressor internal temperature intermittently spiking above 150°C (over-temperature protection threshold). Checked external cooling system: normal. Measured sensor resistance; found abnormal temperature-resistance characteristics (resistance drift). Diagnosed as sensor degradation. Replaced compressor assembly; fault completely resolved.
BYD DTC AI Analysis

Compressor Internal Mechanical Failure with Temperature Sensor Malfunction

✓
The BYD EV had poor air conditioning performance with high low-side pressure, low high-side pressure, and ice on the low-pressure lines. The diagnostic scanner detected DTC B2AB349 and other compressor fault codes. Removed the compressor and found abnormal wear on the scroll plate surfaces, plus friction damage to the internal temperature sensor wiring. Internal mechanical seizure caused overheating, damaging the temperature sensor. Replaced the scroll plate assembly with an improved design (addresses early design defect) or replaced the complete compressor. Refilled with special POE refrigerant oil and the system returned to normal.
Original source ↗
Other Atto 8 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.