AU
B2AB3-49

This DTC indicates a fault in the internal temperature monitoring circuit of the electric air conditioning compressor (E-Compressor) — Atto 3

Thermal Management System

This DTC indicates a fault in the internal temperature monitoring circuit of the electric air conditioning compressor (E-Compressor).

Specifically, the compressor control module (IPM) detects the internal NTC thermistor signal falls outside the valid range (open circuit, short circuit, or signal drift).

As a result, the module cannot accurately read the real-time temperature of the compressor motor windings or power module.

This failure disables the thermal management strategy.

To prevent overheating damage, the system forces the compressor off, directly degrading air conditioning cooling performance and disrupting the battery pack thermal management loop.

In severe cases, the system fails to cool the traction battery effectively.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Compressor internal temperature sensor (NTC thermistor) aging, open circuit, or short circuit
  • 2Backed-out terminals, poor contact, or corrosion at the compressor low-voltage wiring harness connector (commonly at connector G09)
  • 3Compressor cooling circuit fault (insufficient coolant, electronic water pump failure, or radiator blockage) causes actual overheating and triggers protection.
  • 4Compressor control board (IPM/IGBT module) sampling circuit fault, falsely reporting abnormal temperature
  • 5Abnormal compressor supply voltage (high voltage or 12V low voltage fluctuation) causes unstable operation of the temperature sampling circuit.
What To Do
  • 1
    Use the dedicated diagnostic tool to read the DTC freeze frame and record the temperature, high voltage, and compressor speed when the fault occurred.
  • 2
    Check the compressor low-voltage wiring harness connectors (G09, etc.) for backed-out pins, looseness, or water corrosion. Measure the terminal resistance.
  • 3
    Disconnect the compressor connector and measure the internal temperature sensor resistance to verify the sensor condition (reference: approximately 10 kΩ at 25°C; refer to the standard curve in the workshop manual).
  • 4
    Check the compressor cooling system (if equipped with an independent cooling circuit): verify the coolant level, electric water pump operation, and cooling pipe flow.
  • 5
    Check the compressor high-voltage interlock circuit and the 12V control power supply stability to eliminate power supply interference.
  • 6
    If sensor resistance is abnormal or the compressor has an internal fault, replace the electric compressor assembly (the temperature sensor is usually integrated into the compressor and not supplied separately).
  • 7
    After replacement, perform the compressor run-in procedure (if applicable) and verify the thermal management system operates normally.
Real-World Cases
BYD DTC AI Analysis

Qin Pro EV AC not cooling, replaced compressor assembly

✓
Vehicle presented with intermittent AC failure. Retrieved DTC B2AB3-49 (internal temperature sensor fault). Measured infinite resistance (open circuit) between pins G09-4/5 of the compressor harness connector; normal range is 5-15kΩ at 25°C ambient. Diagnosed open circuit in the compressor internal NTC sensor. Replaced the electric compressor assembly. New compressor sensor measured 9.8kΩ. Cleared fault codes. AC system returned to normal. Battery cooling circuit working normally.
BYD DTC AI Analysis

Backed-out wiring harness connector pin caused false DTC on BYD Song DM

✓
While driving, the air conditioning intermittently stopped working and the dashboard displayed "Thermal Management System Fault". The scan tool read DTC B2AB3-49. Inspection revealed pin 14 of the compressor low-voltage connector G09 (temperature sensor signal line) had backed out, causing poor contact. Re-secured the pin and applied conductive grease. The sensor signal voltage tested normal (0.5-4.5V varying with temperature) and the fault cleared. This case shows mechanical connection faults can trigger sensor DTCs.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV300 compressor overheat protection trigger sensor fault

✓
In high summer temperatures, the AC failed after prolonged high-speed driving, setting DTC B2AB3-49. The compressor coolant pump had stopped working, pushing actual compressor temperature above 120°C and triggering protective open circuit or signal drift in the internal sensor. Repaired the pump power supply circuit (blown fuse) and topped up coolant. Compressor temperature returned to normal and the fault code has not returned. Peripheral thermal management faults can trigger this code.
BYD DTC AI Analysis

Software update resolves false fault codes on Qin Pro DM

✓
The vehicle had no actual air conditioning performance issues, but intermittently set DTC B2AB3-49. Inspected the compressor sensor wiring and the sensor itself; both tested normal. Per a technical service bulletin, the compressor control software on this batch has sampling thresholds set too tight. Updated the AC controller and compressor control module software to version V2.1.3 or above. The fault code cleared and has not returned during one week of monitoring. The control strategy caused this false positive.
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.