AU
B2AB6-4B

DTC B2AB6-4B indicates the Electric A/C Compressor internal temperature sensor detects a temperature outside the normal operating range (typically >120°C or an abnormal temperature rise rate) — Atto 8

Thermal Management System

DTC B2AB6-4B indicates the Electric A/C Compressor internal temperature sensor detects a temperature outside the normal operating range (typically >120°C or an abnormal temperature rise rate).

This fault indicates the compressor internal thermal protection mechanism triggered.

Electrical insulation failure, mechanical friction overheating, abnormal controller drive, or refrigerant circulation faults can cause this condition.

This fault disables the air conditioning cooling function.

In severe cases, thermal management system anomalies may trigger the 'EV Function Limited' protection mode, restricting the vehicle's pure electric driving capability.

It typically does not affect high-voltage system safety.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Internal insulation failure in the electric compressor (short to ground or insulation resistance <0.5MΩ), causing leakage current to convert into heat.
  • 2Compressor Controller fault causing abnormal drive current or loss of speed control, resulting in overheating.
  • 3Scroll plate wear or design defect (early version without sealing ring), causing internal leakage, reduced compression efficiency, and abnormal heat generation.
  • 4A/C thermostat or electronic expansion valve fault causes abnormal system pressures (high pressure too high / low pressure too low), resulting in excessive compressor load.
  • 5Refrigerant leak or insufficient POE compressor oil, causing poor lubrication and reduced heat dissipation.
What To Do
  • 1
    Connect the VDS diagnostic tool to read the complete fault codes. Check for accompanying fault codes such as B2AB573 (operation unsuccessful) and B2AB41D (internal current too high), and record the compressor speed, current, and temperature data streams.
  • 2
    Use a megohmmeter to measure the insulation resistance between the electric compressor high-voltage terminal and ground. Normal value: >20MΩ. A reading <0.5MΩ confirms insulation failure.
  • 3
    Connect an A/C manifold gauge set to check the refrigerant system pressure. Normal pressure: high side 1.3-1.5 MPa, low side 0.15-0.25 MPa. If the high-side pressure is too high and the low-side pressure is too low, check the thermostat and expansion valve.
  • 4
    Check the compressor controller connector and CAN communication wiring. If necessary, perform a controller swap test to rule out an abnormal control signal.
  • 5
    If the above checks are normal, disassemble the compressor, inspect the scroll plate sealing (on early models, check for a missing sealing ring), and measure the scroll plate clearance.
  • 6
    Replace the faulty component (compressor assembly/controller/thermostat/scroll plate) based on inspection results. Install the improved scroll plate (with sealing ring) and add the specified POE refrigerant oil.
  • 7
    After completing the repair, evacuate the system, charge with the standard amount of refrigerant (usually 450-550g), run the self-learning program, and monitor the compressor internal temperature data stream.
Real-World Cases
BYD DTC AI Analysis

Compressor insulation failure caused abnormal temperature

✓
AC not cooling; vents blowing ambient air. After driving for some time, the instrument cluster displayed 'EV Function Limited'. Diagnosis found DTCs B2AB573 (Operation Unsuccessful) and B2AB64B (Internal Temperature Abnormal). Measured refrigerant compressor insulation resistance to ground at 0.00MΩ, indicating internal insulation failure. System pressures were also abnormal: high-side pressure high, low-side pressure low. Replaced the electric refrigerant compressor and AC thermostat, recharged the refrigerant, and eliminated the fault.
Original source ↗
BYD DTC AI Analysis

Compressor controller fault caused recurring temperature abnormalities

✓
Two days after compressor replacement, the vehicle again failed to cool. Scanned DTCs B2AB41D (excessive internal current), B2AB64B (abnormal internal temperature), and B2AB774 (abnormal speed). Data analysis showed the compressor running continuously at high speed with abnormal thermostat opening. Confirmed the AC controller failed, causing abnormal compressor operation. Replaced the AC controller and cross-verified on another vehicle, completely resolving the fault.
Original source ↗
BYD DTC AI Analysis

Air conditioning system combined fault (thermostat and controller)

✓
Air conditioning completely failed with no cooling. Retrieved fault codes B2AB573 (operation unsuccessful) and B2AB64B (internal temperature abnormal). Troubleshooting found abnormal insulation resistance to ground on the refrigerant compressor, with high-side pressure too high and low-side pressure too low. Replaced the thermostat and recharged refrigerant initially, but the fault persisted. Further inspection found the air conditioning controller also needed replacement. Replaced the controller, thermostat, and refrigerant to fully resolve.
Original source ↗
BYD DTC AI Analysis

Scroll plate design defect causes abnormal internal temperature

✓
Poor AC cooling: high low-side pressure, low high-side pressure, ice on the low-pressure line, no cooling. Removed the compressor and inspected the scroll plates. Found mirror-like surface finish but no internal seal ring (design defect), causing gas leakage and internal bypass that reduced efficiency and created abnormal internal temperatures. Replaced the scroll plates with an improved design featuring seal rings, charged with EV-specific POE refrigeration oil, reinstalled the compressor to the original position, and tested. Outlet temperature dropped to 4°C and cooling performance restored.
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.