AU
B2AB0-49

DTC B2AB0-49 indicates an abnormality in the electric A/C compressor current sampling circuit — Qin Plus

Thermal Management System

DTC B2AB0-49 indicates an abnormality in the electric A/C compressor current sampling circuit.

In electric compressors driven by a three-phase permanent magnet synchronous motor (PMSM), the controller (MCU) monitors the motor phase currents (U/V/W phases) in real time via a Hall effect sensor or precision shunt resistor for field-oriented control (FOC) and overcurrent protection.

This fault indicates the sampling signal exceeds the valid threshold (open circuit, short circuit, or short to power/ground).

Consequently, the compressor controller cannot accurately read the motor current value and triggers a protection mechanism to stop the compressor, impairing A/C cooling and battery thermal management functions.

This is a hardware-level circuit fault, not a software logic error.

The B2AB0-49 fault code on the Qin Plus indicates a medium-severity issue with the electric A/C compressor's current sampling circuit, where the controller cannot accurately read motor current due to signal abnormalities. Common causes include a faulty Hall current sensor or a damaged current sensing resistor on the controller board. The fix requires visiting an authorised dealer. Typical repair cost data is available based on five recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Damaged or aged Hall current sensor inside the electric compressor, causing output signal drift or interruption.
  • 2Current sensing resistor on the compressor controller board (PCB) (typically a milliohm precision resistor) burnt out or has a cold solder joint.
  • 3Poor contact, backed-out terminals, or corrosion from water ingress in the low-voltage signal wiring harness, causing abnormal transmission of the 5V reference voltage or sampling signal.
  • 4Damaged insulation on the compressor high-voltage wiring harness interferes with the low-voltage sampling signal or causes overvoltage damage to the controller internal sampling circuit.
  • 5An inter-turn short circuit or insulation degradation in the compressor motor winding distorts the actual current waveform, triggering abnormal sampling protection.
What To Do
  • 1
    Use the VDS2000/VDS3000 diagnostic tool to read all fault codes. Check for accompanying faults, such as B2AB049 and B2AC000, and record the freeze frame data.
  • 2
    Inspect the electric compressor low-voltage connector (usually located on the top or side of the compressor, 4-5 pins) for looseness, water ingress, or pin oxidation. Measure the connector terminal voltages to verify the power (+12V/+5V), ground (GND), and CAN lines (around 2.5V) are normal.
  • 3
    Disconnect the high-voltage manual service disconnect (MSD) and wait 5 minutes for the high-voltage capacitor to discharge. Measure the insulation resistance to ground for the positive and negative terminals of the compressor high-voltage wiring harness. The resistance must be greater than 500 MΩ (use a 1000 V megohmmeter).
  • 4
    Disconnect the compressor low-pressure connector and use an oscilloscope to check the current sampling signal waveform (if equipped with a Hall sensor, the normal signal is a 0.5-4.5V linear voltage or PWM signal). If the signal is a constant 0V or 5V, this confirms a faulty sensor.
  • 5
    If the external wiring is normal and the fault persists, the compressor internal controller board has failed. Because BYD supplies electric compressors (such as Sanden Behr or Aotecar integrated compressors) as complete assemblies, do not service the controller board separately. Replace the entire electric compressor assembly. Perform refrigerant recovery, vacuum evacuation, and recharge with the standard amount of R134a (approximately 600-800 g, depending on the vehicle model).
  • 6
    After replacement, use the diagnostic tool to perform 'A/C system self-learning' or 'compressor zero-point calibration' (required on some models). Clear the fault code and road test the vehicle. Observe the data stream to verify 'compressor speed' and 'compressor current' change normally when turning on the A/C.
Real-World Cases
BYD DTC AI Analysis

Qin PRO EV compressor Hall sensor intermittent open circuit

✓
The vehicle came in with intermittent A/C cooling failure and intermittent DTC B2AB0-49. Inspection found expanded pin sockets in the compressor low-voltage connector were interrupting Hall sensor power supply when the vehicle vibrated. Re-crimped the pins and applied conductive grease. Fault resolved. This case shows vibration-induced poor contact is a common cause.
BYD DTC AI Analysis

Qin EV300 compressor controller board sampling resistor burnt out

✓
Customer reported complete AC failure. Retrieved active DTC B2AB0-49. Disassembled compressor controller; internal sampling resistor (1mΩ precision resistor) burned out from high voltage surge, surface charred. Traced to previous use of non-standard charging station causing voltage fluctuation. Replaced electric compressor assembly; fault resolved.
BYD DTC AI Analysis

热管理线束磨损导致信号干扰

✓
车辆行驶中空调突然停止，仪表显示热管理系统故障。检查发现前舱左侧空调压缩机低压线束与车架干涉磨损，导致电流采样信号线（黄色）对地短路。修复线束并重新固定走向，添加防护波纹管，故障码清除后未再出现。
BYD DTC AI Analysis

Insufficient refrigerant caused abnormal current fluctuations in the compressor.

✓
DTC B2AB0-49 appeared with B2A0300 (abnormal compressor speed). Inspection found a refrigerant leak at the high- and low-pressure line connections, causing excessive current fluctuation when the compressor ran at low frequency and triggering a false report from the sampling circuit. Recharged the refrigerant and repaired the leak, then reset the compressor control parameters using a diagnostic scanner.
BYD DTC AI Analysis

Software false positive (phantom DTC)

✓
2018 Qin PRO DM intermittently set DTC B2AB0-49 after the multimedia system upgrade. Wiring checked normal. Data stream confirmed current sampling values were normal. Identified as AC controller (AC ECU) software bug. Executed 'AC Controller Program Update' via VDS (V1.2 to V1.4). Fault cleared.
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.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 Qin Plus →Qin Plus 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.