AU
B2AB64B

DTC B2AB64B indicates the electric A/C compressor internal temperature monitoring point detects an abnormally high temperature or an abnormal temperature signal — Atto 3

Thermal Management System

DTC B2AB64B indicates the electric A/C compressor internal temperature monitoring point detects an abnormally high temperature or an abnormal temperature signal.

On 2019 BYD Qin EV models, this fault typically indicates the electric scroll compressor (BYD in-house or third-party supplied) internal motor winding temperature, power module (IPM) temperature, or compressor housing temperature exceeds the normal operating range (typical threshold: 110–130°C).

When this fault occurs, the compressor controller enters protection mode.

It limits compressor speed or stops operation to prevent insulation damage or mechanical seizure.

Because the Qin EV uses the A/C system for battery thermal management (the battery chiller integrates into the A/C circuit), this fault causes loss of cabin cooling and can reduce traction battery cooling capacity, subsequently triggering battery thermal management power derating protection.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Abnormal refrigerant circulation: System refrigerant leak causes insufficient flow, or air/moisture in the refrigerant causes poor compressor cooling and lubrication, resulting in frictional heating of the compressor pump body.
  • 2Compressor temperature sensor fault: An open circuit, short circuit, or resistance drift in the NTC thermistor, as well as water ingress or poor connection at the sensor wiring harness connector, causes a false high-temperature warning.
  • 3Compressor internal mechanical fault: scroll plate wear, bearing seizure due to lack of lubrication, or degraded motor insulation increases operating resistance and copper loss, generating abnormal heat.
  • 4Poor heat dissipation system efficiency: A dirty or clogged condenser, insufficient cooling fan speed, or blocked cooling air duct causes excessive high-side pressure and increases compressor load.
  • 5Electronic control system fault: Compressor controller (inverter) internal IPM module drive fault, current sampling resistor failure, or improper software over-temperature protection threshold setting.
What To Do
  • 1
    Use VDS2000 or the BYD dedicated diagnostic tool to read freeze frame data. Record the compressor speed, high-side pressure, internal temperature, and ambient temperature at the time of the fault to determine whether the condition is actual overheating or a false sensor reading.
  • 2
    Check the air conditioning system refrigerant quantity and purity. Use a refrigerant recovery machine to extract and weigh the refrigerant to check for a low charge (standard quantity: approx. 600-700g, depending on configuration). If necessary, perform a pressure-holding leak test (hold pressure at 1.5MPa; 30-minute pressure drop <0.1MPa).
  • 3
    Measure the compressor temperature sensor resistance (approx. 10 kΩ at 25°C; resistance decreases as temperature increases). Check the sensor wiring harness for continuity and short circuits to ground or power. Inspect the pins in connectors B12/B13 and others for backing out or corrosion.
  • 4
    Check compressor operation: Disconnect the high-voltage service disconnect, measure the compressor three-phase winding resistance (normal value: 0.5–2 Ω, three-phase balance: <5%), and measure the insulation resistance to the housing (>20 MΩ); power on the system and check if the compressor operating current is abnormally high (normal: 6–8 A; >15 A when faulty).
  • 5
    Check the thermal management system heat dissipation capacity: clean debris from the condenser surface, check the electric fan high and low-speed operation and duty cycle control, and verify the cooling fan controller (RFC) operates normally. If necessary, replace the receiver drier, then evacuate and recharge the system with the standard amount of refrigerant.
  • 6
    If the above checks are normal but the fault occurs intermittently, replace the compressor assembly (with controller) and verify the software version (on some early vehicles, update the compressor controller software to the latest version to optimize the over-temperature protection strategy).
Real-World Cases
BYD DTC AI Analysis

Minor refrigerant leak triggered compressor thermal protection.

✓
2019 Qin EV, 80,000 km. After 30 minutes of summer highway driving, the air conditioning suddenly stopped cooling. No warning lights on the dash, but DTC B2AB64B logged. Freeze frame showed compressor internal temperature at 128°C (threshold 125°C) and high-side pressure at 2.8 MPa (elevated). Inspection found oil residue at the lower left corner of the condenser; a pressure test revealed a minor leak. Recovered only 450g of refrigerant (standard 650g). Replaced the condenser and seals, recharged the refrigerant, and ran continuous high-speed testing for 2 hours. Compressor internal temperature stabilized at 85-95°C. Fault resolved.
BYD DTC AI Analysis

Loose connection in compressor temperature sensor wiring harness causing false alarms

✓
Vehicle intermittently logged DTC B2AB64B approximately once per week, clearing after restart. Diagnostic tool showed internal temperature of -40°C when fault occurred (sensor open-circuit value). Checked compressor controller connector B12: pin 3 (temperature signal) had loose retention and detached when lightly pulled. Repaired pin, applied conductive grease, and re-secured harness routing to prevent vibration interference. No recurrence after 3 months.
BYD DTC AI Analysis

Seized compressor bearing caused high temperature

✓
At 60,000 km, the vehicle emitted a sharp screech after turning on the air conditioning, then set DTC B2AB64B and shut down the AC. Tore down the compressor: the scroll bearing was grinding dry from oil starvation; increased rotor axial clearance caused rotor-to-stator rubbing, overheating and discoloring the windings locally. Three-phase winding resistance measured 1.2Ω/1.3Ω/0.8Ω (imbalanced) with insulation resistance down to only 2MΩ. Replaced the electric compressor assembly, flushed the AC lines—found substantial metal debris—and replaced the receiver drier and expansion valve. Fault cleared completely.
BYD DTC AI Analysis

High ambient temperature and high battery cooling load caused overheating

✓
40°C summer ambient. During fast charging with battery cooling active, the compressor ran continuously at 6000rpm and set DTC B2AB64B. Insufficient condenser cooling combined with high ambient temperature caused the fault. The cooling fan ran at high speed, but condenser fins were severely clogged with catkins. After deep-cleaning the condenser, compressor internal temperature dropped from 122°C to 105°C under identical conditions; protection did not trigger again. Advised owner to clean the condenser regularly, particularly during pollen and catkin season.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.