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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) — Seal 6 EV

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.

The B2AB6-4B fault code on the Seal 6 EV indicates the electric A/C compressor internal temperature is too high or rising abnormally, triggering thermal protection and disabling cabin cooling. Severity is medium; it usually does not affect high-voltage safety but may limit EV function in severe cases. Common causes include compressor insulation failure or a faulty compressor controller. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Electric compressor internal insulation failure (short to ground or insulation resistance <0.5 MΩ), causing leakage current to convert into heat.
  • 2Compressor controller fault causes abnormal drive current or loss of speed control, resulting in overheating.
  • 3Scroll plate wear or design defect (early version without sealing ring), causing internal gas blow-by, reduced compression efficiency, and abnormal heat generation.
  • 4A/C thermostat / electronic expansion valve fault causes abnormal system pressures (high-side pressure too high / low-side pressure too low), resulting in excessive compressor load.
  • 5Refrigerant leak or insufficient POE compressor oil, resulting in poor lubrication and reduced heat dissipation.
What To Do
  • 1
    Connect the VDS diagnostic tool to read the complete fault codes. Check for accompanying related fault codes such as B2AB573 (operation unsuccessful) and B2AB41D (excessive internal current). Record the compressor speed, current, and temperature data stream.
  • 2
    Use a megohmmeter to measure the insulation resistance between the electric compressor high-voltage terminal and ground. The normal value is >20MΩ. A reading <0.5MΩ confirms insulation failure.
  • 3
    Connect an A/C pressure gauge to check the refrigerant system pressure. Normal high pressure is 1.3-1.5 MPa and normal low pressure is 0.15-0.25 MPa. If the high pressure is abnormally high and the low pressure is abnormally 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, check the scroll plate sealing (for early models, check for a missing sealing ring), and measure the scroll plate clearance.
  • 6
    Replace the faulty component based on the inspection results (compressor assembly/controller/thermostat/scroll plate). Install the improved scroll plate (with sealing ring) and add the specified POE refrigerant oil.
  • 7
    After repair, evacuate the system, charge with the standard amount of refrigerant (usually 450-550g), run the self-learning procedure, and monitor the compressor internal temperature data stream.
Real-World Cases
BYD DTC AI Analysis

Compressor insulation failure caused abnormal temperature

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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

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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)

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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

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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 Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV overview →
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.